diff --git a/src/librustc/back/archive.rs b/src/librustc/back/archive.rs
index a0b38700ecf0a..67140ac1920e3 100644
--- a/src/librustc/back/archive.rs
+++ b/src/librustc/back/archive.rs
@@ -129,12 +129,12 @@ impl<'a> Archive<'a> {
     }
 
     /// Lists all files in an archive
-    pub fn files(&self) -> Vec<~str> {
+    pub fn files(&self) -> Vec<StrBuf> {
         let output = run_ar(self.sess, "t", None, [&self.dst]);
         let output = str::from_utf8(output.output.as_slice()).unwrap();
         // use lines_any because windows delimits output with `\r\n` instead of
         // just `\n`
-        output.lines_any().map(|s| s.to_owned()).collect()
+        output.lines_any().map(|s| s.to_strbuf()).collect()
     }
 
     fn add_archive(&mut self, archive: &Path, name: &str,
diff --git a/src/librustc/back/arm.rs b/src/librustc/back/arm.rs
index 792992833a218..0acee6dd1dfae 100644
--- a/src/librustc/back/arm.rs
+++ b/src/librustc/back/arm.rs
@@ -13,56 +13,57 @@ use driver::config::cfg_os_to_meta_os;
 use metadata::loader::meta_section_name;
 use syntax::abi;
 
-pub fn get_target_strs(target_triple: ~str, target_os: abi::Os) -> target_strs::t {
-    let cc_args = if target_triple.contains("thumb") {
-        vec!("-mthumb".to_owned())
+pub fn get_target_strs(target_triple: StrBuf, target_os: abi::Os) -> target_strs::t {
+    let cc_args = if target_triple.as_slice().contains("thumb") {
+        vec!("-mthumb".to_strbuf())
     } else {
-        vec!("-marm".to_owned())
+        vec!("-marm".to_strbuf())
     };
     return target_strs::t {
-        module_asm: "".to_owned(),
+        module_asm: "".to_strbuf(),
 
-        meta_sect_name: meta_section_name(cfg_os_to_meta_os(target_os)).to_owned(),
+        meta_sect_name:
+            meta_section_name(cfg_os_to_meta_os(target_os)).to_strbuf(),
 
         data_layout: match target_os {
           abi::OsMacos => {
-            "e-p:32:32:32".to_owned() +
-                "-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64" +
-                "-f32:32:32-f64:64:64" +
-                "-v64:64:64-v128:64:128" +
-                "-a0:0:64-n32"
+            "e-p:32:32:32\
+                -i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64\
+                -f32:32:32-f64:64:64\
+                -v64:64:64-v128:64:128\
+                -a0:0:64-n32".to_strbuf()
           }
 
           abi::OsWin32 => {
-            "e-p:32:32:32".to_owned() +
-                "-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64" +
-                "-f32:32:32-f64:64:64" +
-                "-v64:64:64-v128:64:128" +
-                "-a0:0:64-n32"
+            "e-p:32:32:32\
+                -i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64\
+                -f32:32:32-f64:64:64\
+                -v64:64:64-v128:64:128\
+                -a0:0:64-n32".to_strbuf()
           }
 
           abi::OsLinux => {
-            "e-p:32:32:32".to_owned() +
-                "-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64" +
-                "-f32:32:32-f64:64:64" +
-                "-v64:64:64-v128:64:128" +
-                "-a0:0:64-n32"
+            "e-p:32:32:32\
+                -i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64\
+                -f32:32:32-f64:64:64\
+                -v64:64:64-v128:64:128\
+                -a0:0:64-n32".to_strbuf()
           }
 
           abi::OsAndroid => {
-            "e-p:32:32:32".to_owned() +
-                "-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64" +
-                "-f32:32:32-f64:64:64" +
-                "-v64:64:64-v128:64:128" +
-                "-a0:0:64-n32"
+            "e-p:32:32:32\
+                -i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64\
+                -f32:32:32-f64:64:64\
+                -v64:64:64-v128:64:128\
+                -a0:0:64-n32".to_strbuf()
           }
 
           abi::OsFreebsd => {
-            "e-p:32:32:32".to_owned() +
-                "-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64" +
-                "-f32:32:32-f64:64:64" +
-                "-v64:64:64-v128:64:128" +
-                "-a0:0:64-n32"
+            "e-p:32:32:32\
+                -i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64\
+                -f32:32:32-f64:64:64\
+                -v64:64:64-v128:64:128\
+                -a0:0:64-n32".to_strbuf()
           }
         },
 
diff --git a/src/librustc/back/link.rs b/src/librustc/back/link.rs
index 45641d08d1e35..588d30ee4af01 100644
--- a/src/librustc/back/link.rs
+++ b/src/librustc/back/link.rs
@@ -54,15 +54,15 @@ pub enum OutputType {
     OutputTypeExe,
 }
 
-pub fn llvm_err(sess: &Session, msg: ~str) -> ! {
+pub fn llvm_err(sess: &Session, msg: StrBuf) -> ! {
     unsafe {
         let cstr = llvm::LLVMRustGetLastError();
         if cstr == ptr::null() {
-            sess.fatal(msg);
+            sess.fatal(msg.as_slice());
         } else {
             let err = CString::new(cstr, true);
             let err = str::from_utf8_lossy(err.as_bytes());
-            sess.fatal(msg + ": " + err.as_slice());
+            sess.fatal((msg.as_slice() + ": " + err.as_slice()));
         }
     }
 }
@@ -79,7 +79,7 @@ pub fn WriteOutputFile(
             let result = llvm::LLVMRustWriteOutputFile(
                     target, pm, m, output, file_type);
             if !result {
-                llvm_err(sess, "could not write output".to_owned());
+                llvm_err(sess, "could not write output".to_strbuf());
             }
         })
     }
@@ -115,7 +115,7 @@ pub mod write {
     fn target_feature<'a>(sess: &'a Session) -> &'a str {
         match sess.targ_cfg.os {
             abi::OsAndroid => {
-                if "" == sess.opts.cg.target_feature {
+                if "" == sess.opts.cg.target_feature.as_slice() {
                     "+v7"
                 } else {
                     sess.opts.cg.target_feature.as_slice()
@@ -173,8 +173,12 @@ pub mod write {
                 }
             };
 
-            let tm = sess.targ_cfg.target_strs.target_triple.with_c_str(|t| {
-                sess.opts.cg.target_cpu.with_c_str(|cpu| {
+            let tm = sess.targ_cfg
+                         .target_strs
+                         .target_triple
+                         .as_slice()
+                         .with_c_str(|t| {
+                sess.opts.cg.target_cpu.as_slice().with_c_str(|cpu| {
                     target_feature(sess).with_c_str(|features| {
                         llvm::LLVMRustCreateTargetMachine(
                             t, cpu, features,
@@ -201,7 +205,7 @@ pub mod write {
             // If we're verifying or linting, add them to the function pass
             // manager.
             let addpass = |pass: &str| {
-                pass.with_c_str(|s| llvm::LLVMRustAddPass(fpm, s))
+                pass.as_slice().with_c_str(|s| llvm::LLVMRustAddPass(fpm, s))
             };
             if !sess.no_verify() { assert!(addpass("verify")); }
 
@@ -212,7 +216,7 @@ pub mod write {
             }
 
             for pass in sess.opts.cg.passes.iter() {
-                pass.with_c_str(|s| {
+                pass.as_slice().with_c_str(|s| {
                     if !llvm::LLVMRustAddPass(mpm, s) {
                         sess.warn(format!("unknown pass {}, ignoring", *pass));
                     }
@@ -355,7 +359,7 @@ pub mod write {
             assembly.as_str().unwrap().to_owned()];
 
         debug!("{} '{}'", cc, args.connect("' '"));
-        match Process::output(cc, args) {
+        match Process::output(cc.as_slice(), args) {
             Ok(prog) => {
                 if !prog.status.success() {
                     sess.err(format!("linking with `{}` failed: {}", cc, prog.status));
@@ -400,7 +404,7 @@ pub mod write {
             if sess.print_llvm_passes() { add("-debug-pass=Structure"); }
 
             for arg in sess.opts.cg.llvm_args.iter() {
-                add(*arg);
+                add((*arg).as_slice());
             }
         }
 
@@ -527,19 +531,20 @@ pub fn find_crate_id(attrs: &[ast::Attribute], out_filestem: &str) -> CrateId {
     match attr::find_crateid(attrs) {
         None => from_str(out_filestem).unwrap_or_else(|| {
             let mut s = out_filestem.chars().filter(|c| c.is_XID_continue());
-            from_str(s.collect::<~str>()).or(from_str("rust-out")).unwrap()
+            from_str(s.collect::<StrBuf>()
+                      .to_owned()).or(from_str("rust-out")).unwrap()
         }),
         Some(s) => s,
     }
 }
 
-pub fn crate_id_hash(crate_id: &CrateId) -> ~str {
+pub fn crate_id_hash(crate_id: &CrateId) -> StrBuf {
     // This calculates CMH as defined above. Note that we don't use the path of
     // the crate id in the hash because lookups are only done by (name/vers),
     // not by path.
     let mut s = Sha256::new();
     s.input_str(crate_id.short_name_with_version().as_slice());
-    truncated_hash_result(&mut s).slice_to(8).to_owned()
+    truncated_hash_result(&mut s).as_slice().slice_to(8).to_strbuf()
 }
 
 pub fn build_link_meta(krate: &ast::Crate, out_filestem: &str) -> LinkMeta {
@@ -551,10 +556,10 @@ pub fn build_link_meta(krate: &ast::Crate, out_filestem: &str) -> LinkMeta {
     return r;
 }
 
-fn truncated_hash_result(symbol_hasher: &mut Sha256) -> ~str {
+fn truncated_hash_result(symbol_hasher: &mut Sha256) -> StrBuf {
     let output = symbol_hasher.result_bytes();
     // 64 bits should be enough to avoid collisions.
-    output.slice_to(8).to_hex()
+    output.slice_to(8).to_hex().to_strbuf()
 }
 
 
@@ -563,7 +568,7 @@ fn symbol_hash(tcx: &ty::ctxt,
                symbol_hasher: &mut Sha256,
                t: ty::t,
                link_meta: &LinkMeta)
-               -> ~str {
+               -> StrBuf {
     // NB: do *not* use abbrevs here as we want the symbol names
     // to be independent of one another in the crate.
 
@@ -572,16 +577,16 @@ fn symbol_hash(tcx: &ty::ctxt,
     symbol_hasher.input_str("-");
     symbol_hasher.input_str(link_meta.crate_hash.as_str());
     symbol_hasher.input_str("-");
-    symbol_hasher.input_str(encoder::encoded_ty(tcx, t));
+    symbol_hasher.input_str(encoder::encoded_ty(tcx, t).as_slice());
     // Prefix with 'h' so that it never blends into adjacent digits
     let mut hash = StrBuf::from_str("h");
-    hash.push_str(truncated_hash_result(symbol_hasher));
-    hash.into_owned()
+    hash.push_str(truncated_hash_result(symbol_hasher).as_slice());
+    hash
 }
 
-fn get_symbol_hash(ccx: &CrateContext, t: ty::t) -> ~str {
+fn get_symbol_hash(ccx: &CrateContext, t: ty::t) -> StrBuf {
     match ccx.type_hashcodes.borrow().find(&t) {
-        Some(h) => return h.to_str(),
+        Some(h) => return h.to_strbuf(),
         None => {}
     }
 
@@ -595,7 +600,7 @@ fn get_symbol_hash(ccx: &CrateContext, t: ty::t) -> ~str {
 // Name sanitation. LLVM will happily accept identifiers with weird names, but
 // gas doesn't!
 // gas accepts the following characters in symbols: a-z, A-Z, 0-9, ., _, $
-pub fn sanitize(s: &str) -> ~str {
+pub fn sanitize(s: &str) -> StrBuf {
     let mut result = StrBuf::new();
     for c in s.chars() {
         match c {
@@ -630,11 +635,10 @@ pub fn sanitize(s: &str) -> ~str {
     }
 
     // Underscore-qualify anything that didn't start as an ident.
-    let result = result.into_owned();
     if result.len() > 0u &&
-        result[0] != '_' as u8 &&
-        ! char::is_XID_start(result[0] as char) {
-        return "_".to_owned() + result;
+        result.as_slice()[0] != '_' as u8 &&
+        ! char::is_XID_start(result.as_slice()[0] as char) {
+        return ("_" + result.as_slice()).to_strbuf();
     }
 
     return result;
@@ -642,7 +646,7 @@ pub fn sanitize(s: &str) -> ~str {
 
 pub fn mangle<PI: Iterator<PathElem>>(mut path: PI,
                                       hash: Option<&str>,
-                                      vers: Option<&str>) -> ~str {
+                                      vers: Option<&str>) -> StrBuf {
     // Follow C++ namespace-mangling style, see
     // http://en.wikipedia.org/wiki/Name_mangling for more info.
     //
@@ -679,10 +683,10 @@ pub fn mangle<PI: Iterator<PathElem>>(mut path: PI,
     }
 
     n.push_char('E'); // End name-sequence.
-    n.into_owned()
+    n
 }
 
-pub fn exported_name(path: PathElems, hash: &str, vers: &str) -> ~str {
+pub fn exported_name(path: PathElems, hash: &str, vers: &str) -> StrBuf {
     // The version will get mangled to have a leading '_', but it makes more
     // sense to lead with a 'v' b/c this is a version...
     let vers = if vers.len() > 0 && !char::is_XID_start(vers.char_at(0)) {
@@ -695,8 +699,8 @@ pub fn exported_name(path: PathElems, hash: &str, vers: &str) -> ~str {
 }
 
 pub fn mangle_exported_name(ccx: &CrateContext, path: PathElems,
-                            t: ty::t, id: ast::NodeId) -> ~str {
-    let mut hash = StrBuf::from_owned_str(get_symbol_hash(ccx, t));
+                            t: ty::t, id: ast::NodeId) -> StrBuf {
+    let mut hash = get_symbol_hash(ccx, t);
 
     // Paths can be completely identical for different nodes,
     // e.g. `fn foo() { { fn a() {} } { fn a() {} } }`, so we
@@ -723,25 +727,28 @@ pub fn mangle_exported_name(ccx: &CrateContext, path: PathElems,
 
 pub fn mangle_internal_name_by_type_and_seq(ccx: &CrateContext,
                                             t: ty::t,
-                                            name: &str) -> ~str {
+                                            name: &str) -> StrBuf {
     let s = ppaux::ty_to_str(ccx.tcx(), t);
-    let path = [PathName(token::intern(s)),
+    let path = [PathName(token::intern(s.as_slice())),
                 gensym_name(name)];
     let hash = get_symbol_hash(ccx, t);
     mangle(ast_map::Values(path.iter()), Some(hash.as_slice()), None)
 }
 
-pub fn mangle_internal_name_by_path_and_seq(path: PathElems, flav: &str) -> ~str {
+pub fn mangle_internal_name_by_path_and_seq(path: PathElems, flav: &str) -> StrBuf {
     mangle(path.chain(Some(gensym_name(flav)).move_iter()), None, None)
 }
 
-pub fn output_lib_filename(id: &CrateId) -> ~str {
-    format!("{}-{}-{}", id.name, crate_id_hash(id), id.version_or_default())
+pub fn output_lib_filename(id: &CrateId) -> StrBuf {
+    format_strbuf!("{}-{}-{}",
+                   id.name,
+                   crate_id_hash(id),
+                   id.version_or_default())
 }
 
-pub fn get_cc_prog(sess: &Session) -> ~str {
+pub fn get_cc_prog(sess: &Session) -> StrBuf {
     match sess.opts.cg.linker {
-        Some(ref linker) => return linker.to_owned(),
+        Some(ref linker) => return linker.to_strbuf(),
         None => {}
     }
 
@@ -750,23 +757,23 @@ pub fn get_cc_prog(sess: &Session) -> ~str {
     // instead of hard-coded gcc.
     // For win32, there is no cc command, so we add a condition to make it use gcc.
     match sess.targ_cfg.os {
-        abi::OsWin32 => return "gcc".to_owned(),
+        abi::OsWin32 => return "gcc".to_strbuf(),
         _ => {},
     }
 
     get_system_tool(sess, "cc")
 }
 
-pub fn get_ar_prog(sess: &Session) -> ~str {
+pub fn get_ar_prog(sess: &Session) -> StrBuf {
     match sess.opts.cg.ar {
-        Some(ref ar) => return ar.to_owned(),
+        Some(ref ar) => return (*ar).clone(),
         None => {}
     }
 
     get_system_tool(sess, "ar")
 }
 
-fn get_system_tool(sess: &Session, tool: &str) -> ~str {
+fn get_system_tool(sess: &Session, tool: &str) -> StrBuf {
     match sess.targ_cfg.os {
         abi::OsAndroid => match sess.opts.cg.android_cross_path {
             Some(ref path) => {
@@ -774,14 +781,16 @@ fn get_system_tool(sess: &Session, tool: &str) -> ~str {
                     "cc" => "gcc",
                     _ => tool
                 };
-                format!("{}/bin/arm-linux-androideabi-{}", *path, tool_str)
+                format_strbuf!("{}/bin/arm-linux-androideabi-{}",
+                               *path,
+                               tool_str)
             }
             None => {
                 sess.fatal(format!("need Android NDK path for the '{}' tool \
                                     (-C android-cross-path)", tool))
             }
         },
-        _ => tool.to_owned(),
+        _ => tool.to_strbuf(),
     }
 }
 
@@ -1022,7 +1031,7 @@ fn link_staticlib(sess: &Session, obj_filename: &Path, out_filename: &Path) {
                 continue
             }
         };
-        a.add_rlib(&p, name, sess.lto()).unwrap();
+        a.add_rlib(&p, name.as_slice(), sess.lto()).unwrap();
         let native_libs = csearch::get_native_libraries(&sess.cstore, cnum);
         for &(kind, ref lib) in native_libs.iter() {
             let name = match kind {
@@ -1057,7 +1066,11 @@ fn link_natively(sess: &Session, trans: &CrateTranslation, dylib: bool,
     // Invoke the system linker
     debug!("{} {}", cc_prog, cc_args.connect(" "));
     let prog = time(sess.time_passes(), "running linker", (), |()|
-                    Process::output(cc_prog, cc_args.as_slice()));
+                    Process::output(cc_prog.as_slice(),
+                                    cc_args.iter()
+                                           .map(|x| (*x).to_owned())
+                                           .collect::<Vec<_>>()
+                                           .as_slice()));
     match prog {
         Ok(prog) => {
             if !prog.status.success() {
@@ -1096,20 +1109,20 @@ fn link_args(sess: &Session,
              tmpdir: &Path,
              trans: &CrateTranslation,
              obj_filename: &Path,
-             out_filename: &Path) -> Vec<~str> {
+             out_filename: &Path) -> Vec<StrBuf> {
 
     // The default library location, we need this to find the runtime.
     // The location of crates will be determined as needed.
     // FIXME (#9639): This needs to handle non-utf8 paths
     let lib_path = sess.target_filesearch().get_lib_path();
-    let stage: ~str = "-L".to_owned() + lib_path.as_str().unwrap();
+    let stage = ("-L".to_owned() + lib_path.as_str().unwrap()).to_strbuf();
 
     let mut args = vec!(stage);
 
     // FIXME (#9639): This needs to handle non-utf8 paths
     args.push_all([
-        "-o".to_owned(), out_filename.as_str().unwrap().to_owned(),
-        obj_filename.as_str().unwrap().to_owned()]);
+        "-o".to_strbuf(), out_filename.as_str().unwrap().to_strbuf(),
+        obj_filename.as_str().unwrap().to_strbuf()]);
 
     // Stack growth requires statically linking a __morestack function. Note
     // that this is listed *before* all other libraries, even though it may be
@@ -1126,14 +1139,14 @@ fn link_args(sess: &Session,
     // line, but inserting this farther to the left makes the
     // "rust_stack_exhausted" symbol an outstanding undefined symbol, which
     // flags libstd as a required library (or whatever provides the symbol).
-    args.push("-lmorestack".to_owned());
+    args.push("-lmorestack".to_strbuf());
 
     // When linking a dynamic library, we put the metadata into a section of the
     // executable. This metadata is in a separate object file from the main
     // object file, so we link that in here.
     if dylib {
         let metadata = obj_filename.with_extension("metadata.o");
-        args.push(metadata.as_str().unwrap().to_owned());
+        args.push(metadata.as_str().unwrap().to_strbuf());
     }
 
     // We want to prevent the compiler from accidentally leaking in any system
@@ -1144,7 +1157,7 @@ fn link_args(sess: &Session,
     //
     // FIXME(#11937) we should invoke the system linker directly
     if sess.targ_cfg.os != abi::OsWin32 {
-        args.push("-nodefaultlibs".to_owned());
+        args.push("-nodefaultlibs".to_strbuf());
     }
 
     // If we're building a dylib, we don't use --gc-sections because LLVM has
@@ -1152,20 +1165,20 @@ fn link_args(sess: &Session,
     // metadata. If we're building an executable, however, --gc-sections drops
     // the size of hello world from 1.8MB to 597K, a 67% reduction.
     if !dylib && sess.targ_cfg.os != abi::OsMacos {
-        args.push("-Wl,--gc-sections".to_owned());
+        args.push("-Wl,--gc-sections".to_strbuf());
     }
 
     if sess.targ_cfg.os == abi::OsLinux {
         // GNU-style linkers will use this to omit linking to libraries which
         // don't actually fulfill any relocations, but only for libraries which
         // follow this flag. Thus, use it before specifying libraries to link to.
-        args.push("-Wl,--as-needed".to_owned());
+        args.push("-Wl,--as-needed".to_strbuf());
 
         // GNU-style linkers support optimization with -O. GNU ld doesn't need a
         // numeric argument, but other linkers do.
         if sess.opts.optimize == config::Default ||
            sess.opts.optimize == config::Aggressive {
-            args.push("-Wl,-O1".to_owned());
+            args.push("-Wl,-O1".to_strbuf());
         }
     } else if sess.targ_cfg.os == abi::OsMacos {
         // The dead_strip option to the linker specifies that functions and data
@@ -1178,14 +1191,14 @@ fn link_args(sess: &Session,
         // won't get much benefit from dylibs because LLVM will have already
         // stripped away as much as it could. This has not been seen to impact
         // link times negatively.
-        args.push("-Wl,-dead_strip".to_owned());
+        args.push("-Wl,-dead_strip".to_strbuf());
     }
 
     if sess.targ_cfg.os == abi::OsWin32 {
         // Make sure that we link to the dynamic libgcc, otherwise cross-module
         // DWARF stack unwinding will not work.
         // This behavior may be overridden by --link-args "-static-libgcc"
-        args.push("-shared-libgcc".to_owned());
+        args.push("-shared-libgcc".to_strbuf());
 
         // And here, we see obscure linker flags #45. On windows, it has been
         // found to be necessary to have this flag to compile liblibc.
@@ -1212,13 +1225,13 @@ fn link_args(sess: &Session,
         //
         // [1] - https://sourceware.org/bugzilla/show_bug.cgi?id=13130
         // [2] - https://code.google.com/p/go/issues/detail?id=2139
-        args.push("-Wl,--enable-long-section-names".to_owned());
+        args.push("-Wl,--enable-long-section-names".to_strbuf());
     }
 
     if sess.targ_cfg.os == abi::OsAndroid {
         // Many of the symbols defined in compiler-rt are also defined in libgcc.
         // Android linker doesn't like that by default.
-        args.push("-Wl,--allow-multiple-definition".to_owned());
+        args.push("-Wl,--allow-multiple-definition".to_strbuf());
     }
 
     // Take careful note of the ordering of the arguments we pass to the linker
@@ -1263,22 +1276,23 @@ fn link_args(sess: &Session,
     if dylib {
         // On mac we need to tell the linker to let this library be rpathed
         if sess.targ_cfg.os == abi::OsMacos {
-            args.push("-dynamiclib".to_owned());
-            args.push("-Wl,-dylib".to_owned());
+            args.push("-dynamiclib".to_strbuf());
+            args.push("-Wl,-dylib".to_strbuf());
             // FIXME (#9639): This needs to handle non-utf8 paths
             if !sess.opts.cg.no_rpath {
-                args.push("-Wl,-install_name,@rpath/".to_owned() +
-                          out_filename.filename_str().unwrap());
+                args.push(format_strbuf!("-Wl,-install_name,@rpath/{}",
+                                         out_filename.filename_str()
+                                                     .unwrap()));
             }
         } else {
-            args.push("-shared".to_owned())
+            args.push("-shared".to_strbuf())
         }
     }
 
     if sess.targ_cfg.os == abi::OsFreebsd {
-        args.push_all(["-L/usr/local/lib".to_owned(),
-                       "-L/usr/local/lib/gcc46".to_owned(),
-                       "-L/usr/local/lib/gcc44".to_owned()]);
+        args.push_all(["-L/usr/local/lib".to_strbuf(),
+                       "-L/usr/local/lib/gcc46".to_strbuf(),
+                       "-L/usr/local/lib/gcc44".to_strbuf()]);
     }
 
     // FIXME (#2397): At some point we want to rpath our guesses as to
@@ -1295,7 +1309,7 @@ fn link_args(sess: &Session,
     //
     // This is the end of the command line, so this library is used to resolve
     // *all* undefined symbols in all other libraries, and this is intentional.
-    args.push("-lcompiler-rt".to_owned());
+    args.push("-lcompiler-rt".to_strbuf());
 
     // Finally add all the linker arguments provided on the command line along
     // with any #[link_args] attributes found inside the crate
@@ -1317,16 +1331,16 @@ fn link_args(sess: &Session,
 // Also note that the native libraries linked here are only the ones located
 // in the current crate. Upstream crates with native library dependencies
 // may have their native library pulled in above.
-fn add_local_native_libraries(args: &mut Vec<~str>, sess: &Session) {
+fn add_local_native_libraries(args: &mut Vec<StrBuf>, sess: &Session) {
     for path in sess.opts.addl_lib_search_paths.borrow().iter() {
         // FIXME (#9639): This needs to handle non-utf8 paths
-        args.push("-L" + path.as_str().unwrap().to_owned());
+        args.push(("-L" + path.as_str().unwrap().to_owned()).to_strbuf());
     }
 
     let rustpath = filesearch::rust_path();
     for path in rustpath.iter() {
         // FIXME (#9639): This needs to handle non-utf8 paths
-        args.push("-L" + path.as_str().unwrap().to_owned());
+        args.push(("-L" + path.as_str().unwrap().to_owned()).to_strbuf());
     }
 
     // Some platforms take hints about whether a library is static or dynamic.
@@ -1340,21 +1354,21 @@ fn add_local_native_libraries(args: &mut Vec<~str>, sess: &Session) {
             cstore::NativeUnknown | cstore::NativeStatic => {
                 if takes_hints {
                     if kind == cstore::NativeStatic {
-                        args.push("-Wl,-Bstatic".to_owned());
+                        args.push("-Wl,-Bstatic".to_strbuf());
                     } else {
-                        args.push("-Wl,-Bdynamic".to_owned());
+                        args.push("-Wl,-Bdynamic".to_strbuf());
                     }
                 }
-                args.push("-l" + *l);
+                args.push(format_strbuf!("-l{}", *l));
             }
             cstore::NativeFramework => {
-                args.push("-framework".to_owned());
-                args.push(l.to_owned());
+                args.push("-framework".to_strbuf());
+                args.push(l.to_strbuf());
             }
         }
     }
     if takes_hints {
-        args.push("-Wl,-Bdynamic".to_owned());
+        args.push("-Wl,-Bdynamic".to_strbuf());
     }
 }
 
@@ -1363,7 +1377,7 @@ fn add_local_native_libraries(args: &mut Vec<~str>, sess: &Session) {
 // Rust crates are not considered at all when creating an rlib output. All
 // dependencies will be linked when producing the final output (instead of
 // the intermediate rlib version)
-fn add_upstream_rust_crates(args: &mut Vec<~str>, sess: &Session,
+fn add_upstream_rust_crates(args: &mut Vec<StrBuf>, sess: &Session,
                             dylib: bool, tmpdir: &Path,
                             trans: &CrateTranslation) {
     // All of the heavy lifting has previously been accomplished by the
@@ -1405,16 +1419,16 @@ fn add_upstream_rust_crates(args: &mut Vec<~str>, sess: &Session,
     }
 
     // Converts a library file-stem into a cc -l argument
-    fn unlib(config: &config::Config, stem: &str) -> ~str {
+    fn unlib(config: &config::Config, stem: &str) -> StrBuf {
         if stem.starts_with("lib") && config.os != abi::OsWin32 {
-            stem.slice(3, stem.len()).to_owned()
+            stem.slice(3, stem.len()).to_strbuf()
         } else {
-            stem.to_owned()
+            stem.to_strbuf()
         }
     }
 
     // Adds the static "rlib" versions of all crates to the command line.
-    fn add_static_crate(args: &mut Vec<~str>, sess: &Session, tmpdir: &Path,
+    fn add_static_crate(args: &mut Vec<StrBuf>, sess: &Session, tmpdir: &Path,
                         cnum: ast::CrateNum, cratepath: Path) {
         // When performing LTO on an executable output, all of the
         // bytecode from the upstream libraries has already been
@@ -1445,21 +1459,21 @@ fn add_upstream_rust_crates(args: &mut Vec<~str>, sess: &Session,
                         sess.abort_if_errors();
                     }
                 }
-                let dst_str = dst.as_str().unwrap().to_owned();
+                let dst_str = dst.as_str().unwrap().to_strbuf();
                 let mut archive = Archive::open(sess, dst);
                 archive.remove_file(format!("{}.o", name));
                 let files = archive.files();
-                if files.iter().any(|s| s.ends_with(".o")) {
+                if files.iter().any(|s| s.as_slice().ends_with(".o")) {
                     args.push(dst_str);
                 }
             });
         } else {
-            args.push(cratepath.as_str().unwrap().to_owned());
+            args.push(cratepath.as_str().unwrap().to_strbuf());
         }
     }
 
     // Same thing as above, but for dynamic crates instead of static crates.
-    fn add_dynamic_crate(args: &mut Vec<~str>, sess: &Session,
+    fn add_dynamic_crate(args: &mut Vec<StrBuf>, sess: &Session,
                          cratepath: Path) {
         // If we're performing LTO, then it should have been previously required
         // that all upstream rust dependencies were available in an rlib format.
@@ -1468,9 +1482,11 @@ fn add_upstream_rust_crates(args: &mut Vec<~str>, sess: &Session,
         // Just need to tell the linker about where the library lives and
         // what its name is
         let dir = cratepath.dirname_str().unwrap();
-        if !dir.is_empty() { args.push("-L" + dir); }
+        if !dir.is_empty() {
+            args.push(format_strbuf!("-L{}", dir));
+        }
         let libarg = unlib(&sess.targ_cfg, cratepath.filestem_str().unwrap());
-        args.push("-l" + libarg);
+        args.push(format_strbuf!("-l{}", libarg));
     }
 }
 
@@ -1492,7 +1508,7 @@ fn add_upstream_rust_crates(args: &mut Vec<~str>, sess: &Session,
 // generic function calls a native function, then the generic function must
 // be instantiated in the target crate, meaning that the native symbol must
 // also be resolved in the target crate.
-fn add_upstream_native_libraries(args: &mut Vec<~str>, sess: &Session) {
+fn add_upstream_native_libraries(args: &mut Vec<StrBuf>, sess: &Session) {
     // Be sure to use a topological sorting of crates because there may be
     // interdependencies between native libraries. When passing -nodefaultlibs,
     // for example, almost all native libraries depend on libc, so we have to
@@ -1507,10 +1523,12 @@ fn add_upstream_native_libraries(args: &mut Vec<~str>, sess: &Session) {
         let libs = csearch::get_native_libraries(&sess.cstore, cnum);
         for &(kind, ref lib) in libs.iter() {
             match kind {
-                cstore::NativeUnknown => args.push("-l" + *lib),
+                cstore::NativeUnknown => {
+                    args.push(format_strbuf!("-l{}", *lib))
+                }
                 cstore::NativeFramework => {
-                    args.push("-framework".to_owned());
-                    args.push(lib.to_owned());
+                    args.push("-framework".to_strbuf());
+                    args.push(lib.to_strbuf());
                 }
                 cstore::NativeStatic => {
                     sess.bug("statics shouldn't be propagated");
diff --git a/src/librustc/back/lto.rs b/src/librustc/back/lto.rs
index f581b7a38a80e..74ac972e5c4b2 100644
--- a/src/librustc/back/lto.rs
+++ b/src/librustc/back/lto.rs
@@ -20,7 +20,7 @@ use libc;
 use flate;
 
 pub fn run(sess: &session::Session, llmod: ModuleRef,
-           tm: TargetMachineRef, reachable: &[~str]) {
+           tm: TargetMachineRef, reachable: &[StrBuf]) {
     if sess.opts.cg.prefer_dynamic {
         sess.err("cannot prefer dynamic linking when performing LTO");
         sess.note("only 'staticlib' and 'bin' outputs are supported with LTO");
@@ -67,13 +67,16 @@ pub fn run(sess: &session::Session, llmod: ModuleRef,
             if !llvm::LLVMRustLinkInExternalBitcode(llmod,
                                                     ptr as *libc::c_char,
                                                     bc.len() as libc::size_t) {
-                link::llvm_err(sess, format!("failed to load bc of `{}`", name));
+                link::llvm_err(sess,
+                               (format_strbuf!("failed to load bc of `{}`",
+                                               name)));
             }
         });
     }
 
     // Internalize everything but the reachable symbols of the current module
-    let cstrs: Vec<::std::c_str::CString> = reachable.iter().map(|s| s.to_c_str()).collect();
+    let cstrs: Vec<::std::c_str::CString> =
+        reachable.iter().map(|s| s.as_slice().to_c_str()).collect();
     let arr: Vec<*i8> = cstrs.iter().map(|c| c.with_ref(|p| p)).collect();
     let ptr = arr.as_ptr();
     unsafe {
diff --git a/src/librustc/back/mips.rs b/src/librustc/back/mips.rs
index ddf67ae564a3e..d044d75ee7743 100644
--- a/src/librustc/back/mips.rs
+++ b/src/librustc/back/mips.rs
@@ -13,51 +13,52 @@ use driver::config::cfg_os_to_meta_os;
 use metadata::loader::meta_section_name;
 use syntax::abi;
 
-pub fn get_target_strs(target_triple: ~str, target_os: abi::Os) -> target_strs::t {
+pub fn get_target_strs(target_triple: StrBuf, target_os: abi::Os) -> target_strs::t {
     return target_strs::t {
-        module_asm: "".to_owned(),
+        module_asm: "".to_strbuf(),
 
-        meta_sect_name: meta_section_name(cfg_os_to_meta_os(target_os)).to_owned(),
+        meta_sect_name:
+            meta_section_name(cfg_os_to_meta_os(target_os)).to_strbuf(),
 
         data_layout: match target_os {
           abi::OsMacos => {
-            "E-p:32:32:32".to_owned() +
-                "-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64" +
-                "-f32:32:32-f64:64:64" +
-                "-v64:64:64-v128:64:128" +
-                "-a0:0:64-n32"
+            "E-p:32:32:32\
+                -i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64\
+                -f32:32:32-f64:64:64\
+                -v64:64:64-v128:64:128\
+                -a0:0:64-n32".to_strbuf()
           }
 
           abi::OsWin32 => {
-            "E-p:32:32:32".to_owned() +
-                "-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64" +
-                "-f32:32:32-f64:64:64" +
-                "-v64:64:64-v128:64:128" +
-                "-a0:0:64-n32"
+            "E-p:32:32:32\
+                -i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64\
+                -f32:32:32-f64:64:64\
+                -v64:64:64-v128:64:128\
+                -a0:0:64-n32".to_strbuf()
           }
 
           abi::OsLinux => {
-            "E-p:32:32:32".to_owned() +
-                "-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64" +
-                "-f32:32:32-f64:64:64" +
-                "-v64:64:64-v128:64:128" +
-                "-a0:0:64-n32"
+            "E-p:32:32:32\
+                -i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64\
+                -f32:32:32-f64:64:64\
+                -v64:64:64-v128:64:128\
+                -a0:0:64-n32".to_strbuf()
           }
 
           abi::OsAndroid => {
-            "E-p:32:32:32".to_owned() +
-                "-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64" +
-                "-f32:32:32-f64:64:64" +
-                "-v64:64:64-v128:64:128" +
-                "-a0:0:64-n32"
+            "E-p:32:32:32\
+                -i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64\
+                -f32:32:32-f64:64:64\
+                -v64:64:64-v128:64:128\
+                -a0:0:64-n32".to_strbuf()
           }
 
           abi::OsFreebsd => {
-            "E-p:32:32:32".to_owned() +
-                "-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64" +
-                "-f32:32:32-f64:64:64" +
-                "-v64:64:64-v128:64:128" +
-                "-a0:0:64-n32"
+            "E-p:32:32:32\
+                -i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64\
+                -f32:32:32-f64:64:64\
+                -v64:64:64-v128:64:128\
+                -a0:0:64-n32".to_strbuf()
           }
         },
 
diff --git a/src/librustc/back/rpath.rs b/src/librustc/back/rpath.rs
index c49adce904a51..8557cfc0bc2bb 100644
--- a/src/librustc/back/rpath.rs
+++ b/src/librustc/back/rpath.rs
@@ -22,7 +22,7 @@ fn not_win32(os: abi::Os) -> bool {
   os != abi::OsWin32
 }
 
-pub fn get_rpath_flags(sess: &Session, out_filename: &Path) -> Vec<~str> {
+pub fn get_rpath_flags(sess: &Session, out_filename: &Path) -> Vec<StrBuf> {
     let os = sess.targ_cfg.os;
 
     // No rpath on windows
@@ -33,9 +33,9 @@ pub fn get_rpath_flags(sess: &Session, out_filename: &Path) -> Vec<~str> {
     let mut flags = Vec::new();
 
     if sess.targ_cfg.os == abi::OsFreebsd {
-        flags.push_all(["-Wl,-rpath,/usr/local/lib/gcc46".to_owned(),
-                        "-Wl,-rpath,/usr/local/lib/gcc44".to_owned(),
-                        "-Wl,-z,origin".to_owned()]);
+        flags.push_all(["-Wl,-rpath,/usr/local/lib/gcc46".to_strbuf(),
+                        "-Wl,-rpath,/usr/local/lib/gcc44".to_strbuf(),
+                        "-Wl,-z,origin".to_strbuf()]);
     }
 
     debug!("preparing the RPATH!");
@@ -47,16 +47,19 @@ pub fn get_rpath_flags(sess: &Session, out_filename: &Path) -> Vec<~str> {
         l.map(|p| p.clone())
     }).collect::<Vec<_>>();
 
-    let rpaths = get_rpaths(os, sysroot, output, libs.as_slice(),
-                            sess.opts.target_triple);
+    let rpaths = get_rpaths(os,
+                            sysroot,
+                            output,
+                            libs.as_slice(),
+                            sess.opts.target_triple.as_slice());
     flags.push_all(rpaths_to_flags(rpaths.as_slice()).as_slice());
     flags
 }
 
-pub fn rpaths_to_flags(rpaths: &[~str]) -> Vec<~str> {
+pub fn rpaths_to_flags(rpaths: &[StrBuf]) -> Vec<StrBuf> {
     let mut ret = Vec::new();
     for rpath in rpaths.iter() {
-        ret.push("-Wl,-rpath," + *rpath);
+        ret.push(("-Wl,-rpath," + (*rpath).as_slice()).to_strbuf());
     }
     return ret;
 }
@@ -65,7 +68,7 @@ fn get_rpaths(os: abi::Os,
               sysroot: &Path,
               output: &Path,
               libs: &[Path],
-              target_triple: &str) -> Vec<~str> {
+              target_triple: &str) -> Vec<StrBuf> {
     debug!("sysroot: {}", sysroot.display());
     debug!("output: {}", output.display());
     debug!("libs:");
@@ -82,7 +85,7 @@ fn get_rpaths(os: abi::Os,
     // And a final backup rpath to the global library location.
     let fallback_rpaths = vec!(get_install_prefix_rpath(sysroot, target_triple));
 
-    fn log_rpaths(desc: &str, rpaths: &[~str]) {
+    fn log_rpaths(desc: &str, rpaths: &[StrBuf]) {
         debug!("{} rpaths:", desc);
         for rpath in rpaths.iter() {
             debug!("    {}", *rpath);
@@ -102,14 +105,14 @@ fn get_rpaths(os: abi::Os,
 
 fn get_rpaths_relative_to_output(os: abi::Os,
                                  output: &Path,
-                                 libs: &[Path]) -> Vec<~str> {
+                                 libs: &[Path]) -> Vec<StrBuf> {
     libs.iter().map(|a| get_rpath_relative_to_output(os, output, a)).collect()
 }
 
 pub fn get_rpath_relative_to_output(os: abi::Os,
                                     output: &Path,
                                     lib: &Path)
-                                 -> ~str {
+                                 -> StrBuf {
     use std::os;
 
     assert!(not_win32(os));
@@ -129,10 +132,11 @@ pub fn get_rpath_relative_to_output(os: abi::Os,
     let relative = lib.path_relative_from(&output);
     let relative = relative.expect("could not create rpath relative to output");
     // FIXME (#9639): This needs to handle non-utf8 paths
-    prefix+"/"+relative.as_str().expect("non-utf8 component in path")
+    (prefix + "/" + relative.as_str()
+                            .expect("non-utf8 component in path")).to_strbuf()
 }
 
-pub fn get_install_prefix_rpath(sysroot: &Path, target_triple: &str) -> ~str {
+pub fn get_install_prefix_rpath(sysroot: &Path, target_triple: &str) -> StrBuf {
     let install_prefix = option_env!("CFG_PREFIX").expect("CFG_PREFIX");
 
     let tlib = filesearch::relative_target_lib_path(sysroot, target_triple);
@@ -140,10 +144,10 @@ pub fn get_install_prefix_rpath(sysroot: &Path, target_triple: &str) -> ~str {
     path.push(&tlib);
     let path = os::make_absolute(&path);
     // FIXME (#9639): This needs to handle non-utf8 paths
-    path.as_str().expect("non-utf8 component in rpath").to_owned()
+    path.as_str().expect("non-utf8 component in rpath").to_strbuf()
 }
 
-pub fn minimize_rpaths(rpaths: &[~str]) -> Vec<~str> {
+pub fn minimize_rpaths(rpaths: &[StrBuf]) -> Vec<StrBuf> {
     let mut set = HashSet::new();
     let mut minimized = Vec::new();
     for rpath in rpaths.iter() {
@@ -163,8 +167,13 @@ mod test {
 
     #[test]
     fn test_rpaths_to_flags() {
-        let flags = rpaths_to_flags(["path1".to_owned(), "path2".to_owned()]);
-        assert_eq!(flags, vec!("-Wl,-rpath,path1".to_owned(), "-Wl,-rpath,path2".to_owned()));
+        let flags = rpaths_to_flags([
+            "path1".to_strbuf(),
+            "path2".to_strbuf()
+        ]);
+        assert_eq!(flags,
+                   vec!("-Wl,-rpath,path1".to_strbuf(),
+                        "-Wl,-rpath,path2".to_strbuf()));
     }
 
     #[test]
@@ -190,18 +199,37 @@ mod test {
 
     #[test]
     fn test_minimize1() {
-        let res = minimize_rpaths(["rpath1".to_owned(), "rpath2".to_owned(), "rpath1".to_owned()]);
-        assert!(res.as_slice() == ["rpath1".to_owned(), "rpath2".to_owned()]);
+        let res = minimize_rpaths([
+            "rpath1".to_strbuf(),
+            "rpath2".to_strbuf(),
+            "rpath1".to_strbuf()
+        ]);
+        assert!(res.as_slice() == [
+            "rpath1".to_strbuf(),
+            "rpath2".to_strbuf()
+        ]);
     }
 
     #[test]
     fn test_minimize2() {
-        let res = minimize_rpaths(["1a".to_owned(), "2".to_owned(),  "2".to_owned(),
-                                   "1a".to_owned(), "4a".to_owned(), "1a".to_owned(),
-                                   "2".to_owned(),  "3".to_owned(),  "4a".to_owned(),
-                                   "3".to_owned()]);
-        assert!(res.as_slice() == ["1a".to_owned(), "2".to_owned(), "4a".to_owned(),
-                                   "3".to_owned()]);
+        let res = minimize_rpaths([
+            "1a".to_strbuf(),
+            "2".to_strbuf(),
+            "2".to_strbuf(),
+            "1a".to_strbuf(),
+            "4a".to_strbuf(),
+            "1a".to_strbuf(),
+            "2".to_strbuf(),
+            "3".to_strbuf(),
+            "4a".to_strbuf(),
+            "3".to_strbuf()
+        ]);
+        assert!(res.as_slice() == [
+            "1a".to_strbuf(),
+            "2".to_strbuf(),
+            "4a".to_strbuf(),
+            "3".to_strbuf()
+        ]);
     }
 
     #[test]
diff --git a/src/librustc/back/svh.rs b/src/librustc/back/svh.rs
index 633850f37180d..8a2f7ff197650 100644
--- a/src/librustc/back/svh.rs
+++ b/src/librustc/back/svh.rs
@@ -54,13 +54,13 @@ use syntax::ast;
 
 #[deriving(Clone, Eq)]
 pub struct Svh {
-    hash: ~str,
+    hash: StrBuf,
 }
 
 impl Svh {
     pub fn new(hash: &str) -> Svh {
         assert!(hash.len() == 16);
-        Svh { hash: hash.to_owned() }
+        Svh { hash: hash.to_strbuf() }
     }
 
     pub fn as_str<'a>(&'a self) -> &'a str {
diff --git a/src/librustc/back/target_strs.rs b/src/librustc/back/target_strs.rs
index e8cdbbdad48cd..9dc85dfe39667 100644
--- a/src/librustc/back/target_strs.rs
+++ b/src/librustc/back/target_strs.rs
@@ -11,9 +11,9 @@
 #![allow(non_camel_case_types)]
 
 pub struct t {
-    pub module_asm: ~str,
-    pub meta_sect_name: ~str,
-    pub data_layout: ~str,
-    pub target_triple: ~str,
-    pub cc_args: Vec<~str> ,
+    pub module_asm: StrBuf,
+    pub meta_sect_name: StrBuf,
+    pub data_layout: StrBuf,
+    pub target_triple: StrBuf,
+    pub cc_args: Vec<StrBuf> ,
 }
diff --git a/src/librustc/back/x86.rs b/src/librustc/back/x86.rs
index b572b59cf6e3b..68a5d4d2ce2c2 100644
--- a/src/librustc/back/x86.rs
+++ b/src/librustc/back/x86.rs
@@ -14,38 +14,41 @@ use driver::config::cfg_os_to_meta_os;
 use metadata::loader::meta_section_name;
 use syntax::abi;
 
-pub fn get_target_strs(target_triple: ~str, target_os: abi::Os) -> target_strs::t {
+pub fn get_target_strs(target_triple: StrBuf, target_os: abi::Os)
+                       -> target_strs::t {
     return target_strs::t {
-        module_asm: "".to_owned(),
+        module_asm: "".to_strbuf(),
 
-        meta_sect_name: meta_section_name(cfg_os_to_meta_os(target_os)).to_owned(),
+        meta_sect_name:
+            meta_section_name(cfg_os_to_meta_os(target_os)).to_strbuf(),
 
         data_layout: match target_os {
           abi::OsMacos => {
-            "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16".to_owned() +
-                "-i32:32:32-i64:32:64" +
-                "-f32:32:32-f64:32:64-v64:64:64" +
-                "-v128:128:128-a0:0:64-f80:128:128" + "-n8:16:32"
+            "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16\
+                -i32:32:32-i64:32:64\
+                -f32:32:32-f64:32:64-v64:64:64\
+                -v128:128:128-a0:0:64-f80:128:128\
+                -n8:16:32".to_strbuf()
           }
 
           abi::OsWin32 => {
-            "e-p:32:32-f64:64:64-i64:64:64-f80:32:32-n8:16:32".to_owned()
+            "e-p:32:32-f64:64:64-i64:64:64-f80:32:32-n8:16:32".to_strbuf()
           }
 
           abi::OsLinux => {
-            "e-p:32:32-f64:32:64-i64:32:64-f80:32:32-n8:16:32".to_owned()
+            "e-p:32:32-f64:32:64-i64:32:64-f80:32:32-n8:16:32".to_strbuf()
           }
           abi::OsAndroid => {
-            "e-p:32:32-f64:32:64-i64:32:64-f80:32:32-n8:16:32".to_owned()
+            "e-p:32:32-f64:32:64-i64:32:64-f80:32:32-n8:16:32".to_strbuf()
           }
 
           abi::OsFreebsd => {
-            "e-p:32:32-f64:32:64-i64:32:64-f80:32:32-n8:16:32".to_owned()
+            "e-p:32:32-f64:32:64-i64:32:64-f80:32:32-n8:16:32".to_strbuf()
           }
         },
 
         target_triple: target_triple,
 
-        cc_args: vec!("-m32".to_owned()),
+        cc_args: vec!("-m32".to_strbuf()),
     };
 }
diff --git a/src/librustc/back/x86_64.rs b/src/librustc/back/x86_64.rs
index 58f1a72e03c62..d0c72fe46d2a3 100644
--- a/src/librustc/back/x86_64.rs
+++ b/src/librustc/back/x86_64.rs
@@ -14,46 +14,47 @@ use driver::config::cfg_os_to_meta_os;
 use metadata::loader::meta_section_name;
 use syntax::abi;
 
-pub fn get_target_strs(target_triple: ~str, target_os: abi::Os) -> target_strs::t {
+pub fn get_target_strs(target_triple: StrBuf, target_os: abi::Os) -> target_strs::t {
     return target_strs::t {
-        module_asm: "".to_owned(),
+        module_asm: "".to_strbuf(),
 
-        meta_sect_name: meta_section_name(cfg_os_to_meta_os(target_os)).to_owned(),
+        meta_sect_name:
+            meta_section_name(cfg_os_to_meta_os(target_os)).to_strbuf(),
 
         data_layout: match target_os {
           abi::OsMacos => {
-            "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-".to_owned()+
-                "f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-"+
-                "s0:64:64-f80:128:128-n8:16:32:64"
+            "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-\
+                f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-\
+                s0:64:64-f80:128:128-n8:16:32:64".to_strbuf()
           }
 
           abi::OsWin32 => {
             // FIXME: Test this. Copied from linux (#2398)
-            "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-".to_owned()+
-                "f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-"+
-                "s0:64:64-f80:128:128-n8:16:32:64-S128"
+            "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-\
+                f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-\
+                s0:64:64-f80:128:128-n8:16:32:64-S128".to_strbuf()
           }
 
           abi::OsLinux => {
-            "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-".to_owned()+
-                "f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-"+
-                "s0:64:64-f80:128:128-n8:16:32:64-S128"
+            "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-\
+                f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-\
+                s0:64:64-f80:128:128-n8:16:32:64-S128".to_strbuf()
           }
           abi::OsAndroid => {
-            "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-".to_owned()+
-                "f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-"+
-                "s0:64:64-f80:128:128-n8:16:32:64-S128"
+            "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-\
+                f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-\
+                s0:64:64-f80:128:128-n8:16:32:64-S128".to_strbuf()
           }
 
           abi::OsFreebsd => {
-            "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-".to_owned()+
-                "f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-"+
-                "s0:64:64-f80:128:128-n8:16:32:64-S128"
+            "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-\
+                f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-\
+                s0:64:64-f80:128:128-n8:16:32:64-S128".to_strbuf()
           }
         },
 
         target_triple: target_triple,
 
-        cc_args: vec!("-m64".to_owned()),
+        cc_args: vec!("-m64".to_strbuf()),
     };
 }
diff --git a/src/librustc/driver/config.rs b/src/librustc/driver/config.rs
index ef8c8f1f70a47..e9c8d4a58cdef 100644
--- a/src/librustc/driver/config.rs
+++ b/src/librustc/driver/config.rs
@@ -76,7 +76,7 @@ pub struct Options {
     // this.
     pub addl_lib_search_paths: RefCell<HashSet<Path>>,
     pub maybe_sysroot: Option<Path>,
-    pub target_triple: ~str,
+    pub target_triple: StrBuf,
     // User-specified cfg meta items. The compiler itself will add additional
     // items to the crate config, and during parsing the entire crate config
     // will be added to the crate AST node.  This should not be used for
@@ -105,7 +105,7 @@ pub fn basic_options() -> Options {
         output_types: Vec::new(),
         addl_lib_search_paths: RefCell::new(HashSet::new()),
         maybe_sysroot: None,
-        target_triple: driver::host_triple().to_owned(),
+        target_triple: driver::host_triple().to_strbuf(),
         cfg: Vec::new(),
         test: false,
         parse_only: false,
@@ -247,26 +247,26 @@ macro_rules! cgoptions(
             }
         }
 
-        fn parse_opt_string(slot: &mut Option<~str>, v: Option<&str>) -> bool {
+        fn parse_opt_string(slot: &mut Option<StrBuf>, v: Option<&str>) -> bool {
             match v {
-                Some(s) => { *slot = Some(s.to_owned()); true },
+                Some(s) => { *slot = Some(s.to_strbuf()); true },
                 None => false,
             }
         }
 
-        fn parse_string(slot: &mut ~str, v: Option<&str>) -> bool {
+        fn parse_string(slot: &mut StrBuf, v: Option<&str>) -> bool {
             match v {
-                Some(s) => { *slot = s.to_owned(); true },
+                Some(s) => { *slot = s.to_strbuf(); true },
                 None => false,
             }
         }
 
-        fn parse_list(slot: &mut Vec<~str>, v: Option<&str>)
+        fn parse_list(slot: &mut Vec<StrBuf>, v: Option<&str>)
                       -> bool {
             match v {
                 Some(s) => {
                     for s in s.words() {
-                        slot.push(s.to_owned());
+                        slot.push(s.to_strbuf());
                     }
                     true
                 },
@@ -278,23 +278,23 @@ macro_rules! cgoptions(
 ) )
 
 cgoptions!(
-    ar: Option<~str> = (None, parse_opt_string,
+    ar: Option<StrBuf> = (None, parse_opt_string,
         "tool to assemble archives with"),
-    linker: Option<~str> = (None, parse_opt_string,
+    linker: Option<StrBuf> = (None, parse_opt_string,
         "system linker to link outputs with"),
-    link_args: Vec<~str> = (Vec::new(), parse_list,
+    link_args: Vec<StrBuf> = (Vec::new(), parse_list,
         "extra arguments to pass to the linker (space separated)"),
-    target_cpu: ~str = ("generic".to_owned(), parse_string,
+    target_cpu: StrBuf = ("generic".to_strbuf(), parse_string,
         "select target processor (llc -mcpu=help for details)"),
-    target_feature: ~str = ("".to_owned(), parse_string,
+    target_feature: StrBuf = ("".to_strbuf(), parse_string,
         "target specific attributes (llc -mattr=help for details)"),
-    passes: Vec<~str> = (Vec::new(), parse_list,
+    passes: Vec<StrBuf> = (Vec::new(), parse_list,
         "a list of extra LLVM passes to run (space separated)"),
-    llvm_args: Vec<~str> = (Vec::new(), parse_list,
+    llvm_args: Vec<StrBuf> = (Vec::new(), parse_list,
         "a list of arguments to pass to llvm (space separated)"),
     save_temps: bool = (false, parse_bool,
         "save all temporary output files during compilation"),
-    android_cross_path: Option<~str> = (None, parse_opt_string,
+    android_cross_path: Option<StrBuf> = (None, parse_opt_string,
         "the path to the Android NDK"),
     no_rpath: bool = (false, parse_bool,
         "disables setting the rpath in libs/exes"),
@@ -310,7 +310,7 @@ cgoptions!(
         "prefer dynamic linking to static linking"),
     no_integrated_as: bool = (false, parse_bool,
         "use an external assembler rather than LLVM's integrated one"),
-    relocation_model: ~str = ("pic".to_owned(), parse_string,
+    relocation_model: StrBuf = ("pic".to_strbuf(), parse_string,
          "choose the relocation model to use (llc -relocation-model for details)"),
 )
 
@@ -456,13 +456,16 @@ static architecture_abis : &'static [(&'static str, abi::Architecture)] = &'stat
     ("mips",   abi::Mips)];
 
 pub fn build_target_config(sopts: &Options) -> Config {
-    let os = match get_os(sopts.target_triple) {
+    let os = match get_os(sopts.target_triple.as_slice()) {
       Some(os) => os,
       None => early_error("unknown operating system")
     };
-    let arch = match get_arch(sopts.target_triple) {
+    let arch = match get_arch(sopts.target_triple.as_slice()) {
       Some(arch) => arch,
-      None => early_error("unknown architecture: " + sopts.target_triple)
+      None => {
+          early_error("unknown architecture: " +
+                      sopts.target_triple.as_slice())
+      }
     };
     let (int_type, uint_type) = match arch {
       abi::X86 => (ast::TyI32, ast::TyU32),
@@ -541,7 +544,7 @@ pub fn optgroups() -> Vec<getopts::OptGroup> {
 
 
 // Convert strings provided as --cfg [cfgspec] into a crate_cfg
-fn parse_cfgspecs(cfgspecs: Vec<~str> ) -> ast::CrateConfig {
+fn parse_cfgspecs(cfgspecs: Vec<StrBuf> ) -> ast::CrateConfig {
     cfgspecs.move_iter().map(|s| {
         parse::parse_meta_from_source_str("cfgspec".to_strbuf(),
                                           s.to_strbuf(),
@@ -639,7 +642,10 @@ pub fn build_session_options(matches: &getopts::Matches) -> Options {
     }
 
     let sysroot_opt = matches.opt_str("sysroot").map(|m| Path::new(m));
-    let target = matches.opt_str("target").unwrap_or(driver::host_triple().to_owned());
+    let target = match matches.opt_str("target") {
+        Some(supplied_target) => supplied_target.to_strbuf(),
+        None => driver::host_triple().to_strbuf(),
+    };
     let opt_level = {
         if (debugging_opts & NO_OPT) != 0 {
             No
@@ -689,10 +695,14 @@ pub fn build_session_options(matches: &getopts::Matches) -> Options {
         Path::new(s.as_slice())
     }).collect();
 
-    let cfg = parse_cfgspecs(matches.opt_strs("cfg").move_iter().collect());
+    let cfg = parse_cfgspecs(matches.opt_strs("cfg")
+                                    .move_iter()
+                                    .map(|x| x.to_strbuf())
+                                    .collect());
     let test = matches.opt_present("test");
     let write_dependency_info = (matches.opt_present("dep-info"),
-                                 matches.opt_str("dep-info").map(|p| Path::new(p)));
+                                 matches.opt_str("dep-info")
+                                        .map(|p| Path::new(p)));
 
     let print_metas = (matches.opt_present("crate-id"),
                        matches.opt_present("crate-name"),
diff --git a/src/librustc/driver/driver.rs b/src/librustc/driver/driver.rs
index 19f2d33e5b1eb..f5f85d748bb27 100644
--- a/src/librustc/driver/driver.rs
+++ b/src/librustc/driver/driver.rs
@@ -71,9 +71,9 @@ pub fn compile_input(sess: Session,
                                                  &sess);
             let loader = &mut Loader::new(&sess);
             let id = link::find_crate_id(krate.attrs.as_slice(),
-                                         outputs.out_filestem);
-            let (expanded_crate, ast_map) = phase_2_configure_and_expand(&sess, loader,
-                                                                         krate, &id);
+                                         outputs.out_filestem.as_slice());
+            let (expanded_crate, ast_map) =
+                phase_2_configure_and_expand(&sess, loader, krate, &id);
             (outputs, expanded_crate, ast_map)
         };
         write_out_deps(&sess, input, &outputs, &expanded_crate);
@@ -99,14 +99,14 @@ pub fn compile_input(sess: Session,
  * The name used for source code that doesn't originate in a file
  * (e.g. source from stdin or a string)
  */
-pub fn anon_src() -> ~str {
-    "<anon>".to_str()
+pub fn anon_src() -> StrBuf {
+    "<anon>".to_strbuf()
 }
 
-pub fn source_name(input: &Input) -> ~str {
+pub fn source_name(input: &Input) -> StrBuf {
     match *input {
         // FIXME (#9639): This needs to handle non-utf8 paths
-        FileInput(ref ifile) => ifile.as_str().unwrap().to_str(),
+        FileInput(ref ifile) => ifile.as_str().unwrap().to_strbuf(),
         StrInput(_) => anon_src()
     }
 }
@@ -115,14 +115,14 @@ pub enum Input {
     /// Load source from file
     FileInput(Path),
     /// The string is the source
-    StrInput(~str)
+    StrInput(StrBuf)
 }
 
 impl Input {
-    fn filestem(&self) -> ~str {
+    fn filestem(&self) -> StrBuf {
         match *self {
-            FileInput(ref ifile) => ifile.filestem_str().unwrap().to_str(),
-            StrInput(_) => "rust_out".to_owned(),
+            FileInput(ref ifile) => ifile.filestem_str().unwrap().to_strbuf(),
+            StrInput(_) => "rust_out".to_strbuf(),
         }
     }
 }
@@ -354,7 +354,7 @@ pub struct CrateTranslation {
     pub metadata_module: ModuleRef,
     pub link: LinkMeta,
     pub metadata: Vec<u8>,
-    pub reachable: Vec<~str>,
+    pub reachable: Vec<StrBuf>,
     pub crate_formats: dependency_format::Dependencies,
 }
 
@@ -450,7 +450,8 @@ fn write_out_deps(sess: &Session,
                   input: &Input,
                   outputs: &OutputFilenames,
                   krate: &ast::Crate) {
-    let id = link::find_crate_id(krate.attrs.as_slice(), outputs.out_filestem);
+    let id = link::find_crate_id(krate.attrs.as_slice(),
+                                 outputs.out_filestem.as_slice());
 
     let mut out_filenames = Vec::new();
     for output_type in sess.opts.output_types.iter() {
@@ -487,9 +488,9 @@ fn write_out_deps(sess: &Session,
     let result = (|| {
         // Build a list of files used to compile the output and
         // write Makefile-compatible dependency rules
-        let files: Vec<~str> = sess.codemap().files.borrow()
+        let files: Vec<StrBuf> = sess.codemap().files.borrow()
                                    .iter().filter(|fmap| fmap.is_real_file())
-                                   .map(|fmap| fmap.name.to_owned())
+                                   .map(|fmap| fmap.name.to_strbuf())
                                    .collect();
         let mut file = try!(io::File::create(&deps_filename));
         for path in out_filenames.iter() {
@@ -567,7 +568,9 @@ impl pprust::PpAnn for TypedAnnotation {
                 try!(pp::word(&mut s.s, "as"));
                 try!(pp::space(&mut s.s));
                 try!(pp::word(&mut s.s,
-                                ppaux::ty_to_str(tcx, ty::expr_ty(tcx, expr))));
+                              ppaux::ty_to_str(
+                                  tcx,
+                                  ty::expr_ty(tcx, expr)).as_slice()));
                 s.pclose()
             }
             _ => Ok(())
@@ -581,20 +584,26 @@ pub fn pretty_print_input(sess: Session,
                           ppm: ::driver::PpMode,
                           ofile: Option<Path>) {
     let krate = phase_1_parse_input(&sess, cfg, input);
-    let id = link::find_crate_id(krate.attrs.as_slice(), input.filestem());
+    let id = link::find_crate_id(krate.attrs.as_slice(),
+                                 input.filestem().as_slice());
 
     let (krate, ast_map, is_expanded) = match ppm {
         PpmExpanded | PpmExpandedIdentified | PpmTyped => {
             let loader = &mut Loader::new(&sess);
-            let (krate, ast_map) = phase_2_configure_and_expand(&sess, loader,
-                                                                krate, &id);
+            let (krate, ast_map) = phase_2_configure_and_expand(&sess,
+                                                                loader,
+                                                                krate,
+                                                                &id);
             (krate, Some(ast_map), true)
         }
         _ => (krate, None, false)
     };
 
     let src_name = source_name(input);
-    let src = Vec::from_slice(sess.codemap().get_filemap(src_name).src.as_bytes());
+    let src = Vec::from_slice(sess.codemap()
+                                  .get_filemap(src_name.as_slice())
+                                  .src
+                                  .as_bytes());
     let mut rdr = MemReader::new(src);
 
     let out = match ofile {
@@ -666,8 +675,12 @@ pub fn collect_crate_types(session: &Session,
         let iter = attrs.iter().filter_map(|a| {
             if a.name().equiv(&("crate_type")) {
                 match a.value_str() {
-                    Some(ref n) if n.equiv(&("rlib")) => Some(config::CrateTypeRlib),
-                    Some(ref n) if n.equiv(&("dylib")) => Some(config::CrateTypeDylib),
+                    Some(ref n) if n.equiv(&("rlib")) => {
+                        Some(config::CrateTypeRlib)
+                    }
+                    Some(ref n) if n.equiv(&("dylib")) => {
+                        Some(config::CrateTypeDylib)
+                    }
                     Some(ref n) if n.equiv(&("lib")) => {
                         Some(config::default_lib_output())
                     }
@@ -679,12 +692,16 @@ pub fn collect_crate_types(session: &Session,
                         session.add_lint(lint::UnknownCrateType,
                                          ast::CRATE_NODE_ID,
                                          a.span,
-                                         "invalid `crate_type` value".to_owned());
+                                         "invalid `crate_type` \
+                                          value".to_strbuf());
                         None
                     }
                     _ => {
-                        session.add_lint(lint::UnknownCrateType, ast::CRATE_NODE_ID,
-                                        a.span, "`crate_type` requires a value".to_owned());
+                        session.add_lint(lint::UnknownCrateType,
+                                         ast::CRATE_NODE_ID,
+                                         a.span,
+                                         "`crate_type` requires a \
+                                          value".to_strbuf());
                         None
                     }
                 }
@@ -704,7 +721,7 @@ pub fn collect_crate_types(session: &Session,
 
 pub struct OutputFilenames {
     pub out_directory: Path,
-    pub out_filestem: ~str,
+    pub out_filestem: StrBuf,
     pub single_output_file: Option<Path>,
 }
 
@@ -756,7 +773,7 @@ pub fn build_output_filenames(input: &Input,
             let crateid = attr::find_crateid(attrs);
             match crateid {
                 None => {}
-                Some(crateid) => stem = crateid.name.to_str(),
+                Some(crateid) => stem = crateid.name.to_strbuf(),
             }
             OutputFilenames {
                 out_directory: dirpath,
@@ -778,7 +795,7 @@ pub fn build_output_filenames(input: &Input,
             }
             OutputFilenames {
                 out_directory: out_file.dir_path(),
-                out_filestem: out_file.filestem_str().unwrap().to_str(),
+                out_filestem: out_file.filestem_str().unwrap().to_strbuf(),
                 single_output_file: ofile,
             }
         }
diff --git a/src/librustc/driver/mod.rs b/src/librustc/driver/mod.rs
index ec60e2c3e6fcb..db91303b53316 100644
--- a/src/librustc/driver/mod.rs
+++ b/src/librustc/driver/mod.rs
@@ -56,7 +56,8 @@ fn run_compiler(args: &[~str]) {
             let ifile = matches.free.get(0).as_slice();
             if ifile == "-" {
                 let contents = io::stdin().read_to_end().unwrap();
-                let src = str::from_utf8(contents.as_slice()).unwrap().to_owned();
+                let src = str::from_utf8(contents.as_slice()).unwrap()
+                                                             .to_strbuf();
                 (StrInput(src), None)
             } else {
                 (FileInput(Path::new(ifile)), Some(Path::new(ifile)))
@@ -249,9 +250,13 @@ fn print_crate_info(sess: &Session,
     // these nasty nested conditions are to avoid doing extra work
     if crate_id || crate_name || crate_file_name {
         let attrs = parse_crate_attrs(sess, input);
-        let t_outputs = driver::build_output_filenames(input, odir, ofile,
-                                                       attrs.as_slice(), sess);
-        let id = link::find_crate_id(attrs.as_slice(), t_outputs.out_filestem);
+        let t_outputs = driver::build_output_filenames(input,
+                                                       odir,
+                                                       ofile,
+                                                       attrs.as_slice(),
+                                                       sess);
+        let id = link::find_crate_id(attrs.as_slice(),
+                                     t_outputs.out_filestem.as_slice());
 
         if crate_id {
             println!("{}", id.to_str());
diff --git a/src/librustc/driver/session.rs b/src/librustc/driver/session.rs
index 24921efdb782e..b5176d3f4a8dd 100644
--- a/src/librustc/driver/session.rs
+++ b/src/librustc/driver/session.rs
@@ -28,7 +28,6 @@ use syntax::{ast, codemap};
 use std::os;
 use std::cell::{Cell, RefCell};
 
-
 pub struct Session {
     pub targ_cfg: config::Config,
     pub opts: config::Options,
@@ -43,7 +42,7 @@ pub struct Session {
     // expected to be absolute. `None` means that there is no source file.
     pub local_crate_source_file: Option<Path>,
     pub working_dir: Path,
-    pub lints: RefCell<NodeMap<Vec<(lint::Lint, codemap::Span, ~str)>>>,
+    pub lints: RefCell<NodeMap<Vec<(lint::Lint, codemap::Span, StrBuf)>>>,
     pub node_id: Cell<ast::NodeId>,
     pub crate_types: RefCell<Vec<config::CrateType>>,
     pub features: front::feature_gate::Features,
@@ -109,7 +108,7 @@ impl Session {
                     lint: lint::Lint,
                     id: ast::NodeId,
                     sp: Span,
-                    msg: ~str) {
+                    msg: StrBuf) {
         let mut lints = self.lints.borrow_mut();
         match lints.find_mut(&id) {
             Some(arr) => { arr.push((lint, sp, msg)); return; }
@@ -180,10 +179,9 @@ impl Session {
         }
     }
     pub fn target_filesearch<'a>(&'a self) -> filesearch::FileSearch<'a> {
-        filesearch::FileSearch::new(
-            self.sysroot(),
-            self.opts.target_triple,
-            &self.opts.addl_lib_search_paths)
+        filesearch::FileSearch::new(self.sysroot(),
+                                    self.opts.target_triple.as_slice(),
+                                    &self.opts.addl_lib_search_paths)
     }
     pub fn host_filesearch<'a>(&'a self) -> filesearch::FileSearch<'a> {
         filesearch::FileSearch::new(
@@ -245,7 +243,6 @@ pub fn build_session_(sopts: config::Options,
     }
 }
 
-
 // Seems out of place, but it uses session, so I'm putting it here
 pub fn expect<T:Clone>(sess: &Session, opt: Option<T>, msg: || -> StrBuf)
               -> T {
diff --git a/src/librustc/front/feature_gate.rs b/src/librustc/front/feature_gate.rs
index 925d9430ede8c..b6022f5675926 100644
--- a/src/librustc/front/feature_gate.rs
+++ b/src/librustc/front/feature_gate.rs
@@ -359,7 +359,7 @@ pub fn check_crate(sess: &Session, krate: &ast::Crate) {
                             sess.add_lint(lint::UnknownFeatures,
                                           ast::CRATE_NODE_ID,
                                           mi.span,
-                                          "unknown feature".to_owned());
+                                          "unknown feature".to_strbuf());
                         }
                     }
                 }
diff --git a/src/librustc/lib.rs b/src/librustc/lib.rs
index 5b5ec2cdc2157..d11c8898ad4cd 100644
--- a/src/librustc/lib.rs
+++ b/src/librustc/lib.rs
@@ -119,7 +119,6 @@ pub mod lib {
     pub mod llvmdeps;
 }
 
-
 pub fn main() {
     std::os::set_exit_status(driver::main_args(std::os::args().as_slice()));
 }
diff --git a/src/librustc/lib/llvm.rs b/src/librustc/lib/llvm.rs
index 74e332a8db456..e3d0e78e93873 100644
--- a/src/librustc/lib/llvm.rs
+++ b/src/librustc/lib/llvm.rs
@@ -1840,7 +1840,7 @@ pub fn SetFunctionAttribute(fn_: ValueRef, attr: Attribute) {
 /* Memory-managed object interface to type handles. */
 
 pub struct TypeNames {
-    named_types: RefCell<HashMap<~str, TypeRef>>,
+    named_types: RefCell<HashMap<StrBuf, TypeRef>>,
 }
 
 impl TypeNames {
@@ -1851,33 +1851,34 @@ impl TypeNames {
     }
 
     pub fn associate_type(&self, s: &str, t: &Type) {
-        assert!(self.named_types.borrow_mut().insert(s.to_owned(), t.to_ref()));
+        assert!(self.named_types.borrow_mut().insert(s.to_strbuf(),
+                                                     t.to_ref()));
     }
 
     pub fn find_type(&self, s: &str) -> Option<Type> {
         self.named_types.borrow().find_equiv(&s).map(|x| Type::from_ref(*x))
     }
 
-    pub fn type_to_str(&self, ty: Type) -> ~str {
+    pub fn type_to_str(&self, ty: Type) -> StrBuf {
         unsafe {
             let s = llvm::LLVMTypeToString(ty.to_ref());
             let ret = from_c_str(s);
             free(s as *mut c_void);
-            ret
+            ret.to_strbuf()
         }
     }
 
-    pub fn types_to_str(&self, tys: &[Type]) -> ~str {
-        let strs: Vec<~str> = tys.iter().map(|t| self.type_to_str(*t)).collect();
-        format!("[{}]", strs.connect(","))
+    pub fn types_to_str(&self, tys: &[Type]) -> StrBuf {
+        let strs: Vec<StrBuf> = tys.iter().map(|t| self.type_to_str(*t)).collect();
+        format_strbuf!("[{}]", strs.connect(",").to_strbuf())
     }
 
-    pub fn val_to_str(&self, val: ValueRef) -> ~str {
+    pub fn val_to_str(&self, val: ValueRef) -> StrBuf {
         unsafe {
             let s = llvm::LLVMValueToString(val);
             let ret = from_c_str(s);
             free(s as *mut c_void);
-            ret
+            ret.to_strbuf()
         }
     }
 }
diff --git a/src/librustc/metadata/creader.rs b/src/librustc/metadata/creader.rs
index d0b14f9e1302a..eabd316b7c505 100644
--- a/src/librustc/metadata/creader.rs
+++ b/src/librustc/metadata/creader.rs
@@ -120,8 +120,11 @@ fn visit_view_item(e: &mut Env, i: &ast::ViewItem) {
 
     match extract_crate_info(e, i) {
         Some(info) => {
-            let (cnum, _, _) = resolve_crate(e, &None, info.ident,
-                                             &info.crate_id, None,
+            let (cnum, _, _) = resolve_crate(e,
+                                             &None,
+                                             info.ident.as_slice(),
+                                             &info.crate_id,
+                                             None,
                                              i.span);
             e.sess.cstore.add_extern_mod_stmt_cnum(info.id, cnum);
         }
@@ -130,7 +133,7 @@ fn visit_view_item(e: &mut Env, i: &ast::ViewItem) {
 }
 
 struct CrateInfo {
-    ident: ~str,
+    ident: StrBuf,
     crate_id: CrateId,
     id: ast::NodeId,
     should_link: bool,
@@ -156,7 +159,7 @@ fn extract_crate_info(e: &Env, i: &ast::ViewItem) -> Option<CrateInfo> {
                 None => from_str(ident.get().to_str()).unwrap()
             };
             Some(CrateInfo {
-                ident: ident.get().to_str(),
+                ident: ident.get().to_strbuf(),
                 crate_id: crate_id,
                 id: id,
                 should_link: should_link(i),
@@ -237,7 +240,9 @@ fn visit_item(e: &Env, i: &ast::Item) {
                         if n.get().is_empty() {
                             e.sess.span_err(m.span, "#[link(name = \"\")] given with empty name");
                         } else {
-                            e.sess.cstore.add_used_library(n.get().to_owned(), kind);
+                            e.sess
+                             .cstore
+                             .add_used_library(n.get().to_strbuf(), kind);
                         }
                     }
                     None => {}
@@ -279,7 +284,7 @@ fn register_crate<'a>(e: &mut Env,
     // Stash paths for top-most crate locally if necessary.
     let crate_paths = if root.is_none() {
         Some(CratePaths {
-            ident: ident.to_owned(),
+            ident: ident.to_strbuf(),
             dylib: lib.dylib.clone(),
             rlib:  lib.rlib.clone(),
         })
@@ -294,7 +299,7 @@ fn register_crate<'a>(e: &mut Env,
     let loader::Library{ dylib, rlib, metadata } = lib;
 
     let cmeta = Rc::new( cstore::crate_metadata {
-        name: crate_id.name.to_owned(),
+        name: crate_id.name.to_strbuf(),
         data: metadata,
         cnum_map: cnum_map,
         cnum: cnum,
@@ -328,7 +333,7 @@ fn resolve_crate<'a>(e: &mut Env,
                 span: span,
                 ident: ident,
                 crate_id: crate_id,
-                id_hash: id_hash,
+                id_hash: id_hash.as_slice(),
                 hash: hash.map(|a| &*a),
                 filesearch: e.sess.target_filesearch(),
                 os: config::cfg_os_to_meta_os(e.sess.targ_cfg.os),
@@ -391,9 +396,9 @@ impl<'a> CrateLoader for Loader<'a> {
         let mut load_ctxt = loader::Context {
             sess: self.env.sess,
             span: krate.span,
-            ident: info.ident,
+            ident: info.ident.as_slice(),
             crate_id: &info.crate_id,
-            id_hash: id_hash,
+            id_hash: id_hash.as_slice(),
             hash: None,
             filesearch: self.env.sess.host_filesearch(),
             triple: driver::host_triple(),
diff --git a/src/librustc/metadata/csearch.rs b/src/librustc/metadata/csearch.rs
index 5906312b51523..fc5c01d4d8dbf 100644
--- a/src/librustc/metadata/csearch.rs
+++ b/src/librustc/metadata/csearch.rs
@@ -32,7 +32,7 @@ pub struct StaticMethodInfo {
     pub vis: ast::Visibility,
 }
 
-pub fn get_symbol(cstore: &cstore::CStore, def: ast::DefId) -> ~str {
+pub fn get_symbol(cstore: &cstore::CStore, def: ast::DefId) -> StrBuf {
     let cdata = cstore.get_crate_data(def.krate);
     decoder::get_symbol(cdata.data(), def.node)
 }
@@ -86,7 +86,8 @@ pub fn get_item_path(tcx: &ty::ctxt, def: ast::DefId) -> Vec<ast_map::PathElem>
 
     // FIXME #1920: This path is not always correct if the crate is not linked
     // into the root namespace.
-    (vec!(ast_map::PathMod(token::intern(cdata.name)))).append(path.as_slice())
+    (vec!(ast_map::PathMod(token::intern(cdata.name.as_slice())))).append(
+        path.as_slice())
 }
 
 pub enum found_ast {
@@ -245,7 +246,7 @@ pub fn get_impl_vtables(tcx: &ty::ctxt,
 
 pub fn get_native_libraries(cstore: &cstore::CStore,
                             crate_num: ast::CrateNum)
-                                -> Vec<(cstore::NativeLibaryKind, ~str)> {
+                                -> Vec<(cstore::NativeLibaryKind, StrBuf)> {
     let cdata = cstore.get_crate_data(crate_num);
     decoder::get_native_libraries(&*cdata)
 }
diff --git a/src/librustc/metadata/cstore.rs b/src/librustc/metadata/cstore.rs
index 390df9c080989..ede70c94ecb02 100644
--- a/src/librustc/metadata/cstore.rs
+++ b/src/librustc/metadata/cstore.rs
@@ -38,7 +38,7 @@ pub enum MetadataBlob {
 }
 
 pub struct crate_metadata {
-    pub name: ~str,
+    pub name: StrBuf,
     pub data: MetadataBlob,
     pub cnum_map: cnum_map,
     pub cnum: ast::CrateNum,
@@ -71,8 +71,8 @@ pub struct CStore {
     metas: RefCell<HashMap<ast::CrateNum, Rc<crate_metadata>>>,
     extern_mod_crate_map: RefCell<extern_mod_crate_map>,
     used_crate_sources: RefCell<Vec<CrateSource>>,
-    used_libraries: RefCell<Vec<(~str, NativeLibaryKind)>>,
-    used_link_args: RefCell<Vec<~str>>,
+    used_libraries: RefCell<Vec<(StrBuf, NativeLibaryKind)>>,
+    used_link_args: RefCell<Vec<StrBuf>>,
     pub intr: Rc<IdentInterner>,
 }
 
@@ -178,23 +178,23 @@ impl CStore {
         libs
     }
 
-    pub fn add_used_library(&self, lib: ~str, kind: NativeLibaryKind) {
+    pub fn add_used_library(&self, lib: StrBuf, kind: NativeLibaryKind) {
         assert!(!lib.is_empty());
         self.used_libraries.borrow_mut().push((lib, kind));
     }
 
     pub fn get_used_libraries<'a>(&'a self)
-                              -> &'a RefCell<Vec<(~str, NativeLibaryKind)> > {
+                              -> &'a RefCell<Vec<(StrBuf, NativeLibaryKind)> > {
         &self.used_libraries
     }
 
     pub fn add_used_link_args(&self, args: &str) {
         for s in args.split(' ') {
-            self.used_link_args.borrow_mut().push(s.to_owned());
+            self.used_link_args.borrow_mut().push(s.to_strbuf());
         }
     }
 
-    pub fn get_used_link_args<'a>(&'a self) -> &'a RefCell<Vec<~str> > {
+    pub fn get_used_link_args<'a>(&'a self) -> &'a RefCell<Vec<StrBuf> > {
         &self.used_link_args
     }
 
diff --git a/src/librustc/metadata/decoder.rs b/src/librustc/metadata/decoder.rs
index 39700f91b5fed..da21cde3d6cc1 100644
--- a/src/librustc/metadata/decoder.rs
+++ b/src/librustc/metadata/decoder.rs
@@ -184,8 +184,8 @@ fn item_method_sort(item: ebml::Doc) -> char {
     ret
 }
 
-fn item_symbol(item: ebml::Doc) -> ~str {
-    reader::get_doc(item, tag_items_data_item_symbol).as_str()
+fn item_symbol(item: ebml::Doc) -> StrBuf {
+    reader::get_doc(item, tag_items_data_item_symbol).as_str().to_strbuf()
 }
 
 fn item_parent_item(d: ebml::Doc) -> Option<ast::DefId> {
@@ -451,7 +451,7 @@ pub fn get_impl_vtables(cdata: Cmd,
 }
 
 
-pub fn get_symbol(data: &[u8], id: ast::NodeId) -> ~str {
+pub fn get_symbol(data: &[u8], id: ast::NodeId) -> StrBuf {
     return item_symbol(lookup_item(id, data));
 }
 
@@ -1097,13 +1097,15 @@ pub fn get_crate_deps(data: &[u8]) -> Vec<CrateDep> {
     let cratedoc = reader::Doc(data);
     let depsdoc = reader::get_doc(cratedoc, tag_crate_deps);
     let mut crate_num = 1;
-    fn docstr(doc: ebml::Doc, tag_: uint) -> ~str {
+    fn docstr(doc: ebml::Doc, tag_: uint) -> StrBuf {
         let d = reader::get_doc(doc, tag_);
-        d.as_str_slice().to_str()
+        d.as_str_slice().to_strbuf()
     }
     reader::tagged_docs(depsdoc, tag_crate_dep, |depdoc| {
-        let crate_id = from_str(docstr(depdoc, tag_crate_dep_crateid)).unwrap();
-        let hash = Svh::new(docstr(depdoc, tag_crate_dep_hash));
+        let crate_id =
+            from_str(docstr(depdoc,
+                            tag_crate_dep_crateid).as_slice()).unwrap();
+        let hash = Svh::new(docstr(depdoc, tag_crate_dep_hash).as_slice());
         deps.push(CrateDep {
             cnum: crate_num,
             crate_id: crate_id,
@@ -1144,10 +1146,10 @@ pub fn maybe_get_crate_id(data: &[u8]) -> Option<CrateId> {
     })
 }
 
-pub fn get_crate_triple(data: &[u8]) -> ~str {
+pub fn get_crate_triple(data: &[u8]) -> StrBuf {
     let cratedoc = reader::Doc(data);
     let triple_doc = reader::maybe_get_doc(cratedoc, tag_crate_triple);
-    triple_doc.expect("No triple in crate").as_str()
+    triple_doc.expect("No triple in crate").as_str().to_strbuf()
 }
 
 pub fn get_crate_id(data: &[u8]) -> CrateId {
@@ -1239,7 +1241,8 @@ pub fn get_trait_of_method(cdata: Cmd, id: ast::NodeId, tcx: &ty::ctxt)
 }
 
 
-pub fn get_native_libraries(cdata: Cmd) -> Vec<(cstore::NativeLibaryKind, ~str)> {
+pub fn get_native_libraries(cdata: Cmd)
+                            -> Vec<(cstore::NativeLibaryKind, StrBuf)> {
     let libraries = reader::get_doc(reader::Doc(cdata.data()),
                                     tag_native_libraries);
     let mut result = Vec::new();
@@ -1248,7 +1251,7 @@ pub fn get_native_libraries(cdata: Cmd) -> Vec<(cstore::NativeLibaryKind, ~str)>
         let name_doc = reader::get_doc(lib_doc, tag_native_libraries_name);
         let kind: cstore::NativeLibaryKind =
             FromPrimitive::from_u32(reader::doc_as_u32(kind_doc)).unwrap();
-        let name = name_doc.as_str();
+        let name = name_doc.as_str().to_strbuf();
         result.push((kind, name));
         true
     });
@@ -1260,12 +1263,12 @@ pub fn get_macro_registrar_fn(data: &[u8]) -> Option<ast::NodeId> {
         .map(|doc| FromPrimitive::from_u32(reader::doc_as_u32(doc)).unwrap())
 }
 
-pub fn get_exported_macros(data: &[u8]) -> Vec<~str> {
+pub fn get_exported_macros(data: &[u8]) -> Vec<StrBuf> {
     let macros = reader::get_doc(reader::Doc(data),
                                  tag_exported_macros);
     let mut result = Vec::new();
     reader::tagged_docs(macros, tag_macro_def, |macro_doc| {
-        result.push(macro_doc.as_str());
+        result.push(macro_doc.as_str().to_strbuf());
         true
     });
     result
diff --git a/src/librustc/metadata/encoder.rs b/src/librustc/metadata/encoder.rs
index b6bd345d90482..a7ba8300aed68 100644
--- a/src/librustc/metadata/encoder.rs
+++ b/src/librustc/metadata/encoder.rs
@@ -70,7 +70,7 @@ pub struct EncodeParams<'a> {
     pub diag: &'a SpanHandler,
     pub tcx: &'a ty::ctxt,
     pub reexports2: &'a middle::resolve::ExportMap2,
-    pub item_symbols: &'a RefCell<NodeMap<~str>>,
+    pub item_symbols: &'a RefCell<NodeMap<StrBuf>>,
     pub non_inlineable_statics: &'a RefCell<NodeSet>,
     pub link_meta: &'a LinkMeta,
     pub cstore: &'a cstore::CStore,
@@ -81,7 +81,7 @@ pub struct EncodeContext<'a> {
     pub diag: &'a SpanHandler,
     pub tcx: &'a ty::ctxt,
     pub reexports2: &'a middle::resolve::ExportMap2,
-    pub item_symbols: &'a RefCell<NodeMap<~str>>,
+    pub item_symbols: &'a RefCell<NodeMap<StrBuf>>,
     pub non_inlineable_statics: &'a RefCell<NodeSet>,
     pub link_meta: &'a LinkMeta,
     pub cstore: &'a cstore::CStore,
@@ -98,7 +98,7 @@ fn encode_impl_type_basename(ebml_w: &mut Encoder, name: Ident) {
 }
 
 pub fn encode_def_id(ebml_w: &mut Encoder, id: DefId) {
-    ebml_w.wr_tagged_str(tag_def_id, def_to_str(id));
+    ebml_w.wr_tagged_str(tag_def_id, def_to_str(id).as_slice());
 }
 
 #[deriving(Clone)]
@@ -139,8 +139,8 @@ fn encode_family(ebml_w: &mut Encoder, c: char) {
     ebml_w.end_tag();
 }
 
-pub fn def_to_str(did: DefId) -> ~str {
-    format!("{}:{}", did.krate, did.node)
+pub fn def_to_str(did: DefId) -> StrBuf {
+    format_strbuf!("{}:{}", did.krate, did.node)
 }
 
 fn encode_ty_type_param_defs(ebml_w: &mut Encoder,
@@ -170,7 +170,7 @@ fn encode_region_param_defs(ebml_w: &mut Encoder,
         ebml_w.end_tag();
 
         ebml_w.wr_tagged_str(tag_region_param_def_def_id,
-                             def_to_str(param.def_id));
+                             def_to_str(param.def_id).as_slice());
 
         ebml_w.end_tag();
     }
@@ -370,10 +370,12 @@ fn encode_reexported_static_method(ebml_w: &mut Encoder,
             exp.name, token::get_ident(method_ident));
     ebml_w.start_tag(tag_items_data_item_reexport);
     ebml_w.start_tag(tag_items_data_item_reexport_def_id);
-    ebml_w.wr_str(def_to_str(method_def_id));
+    ebml_w.wr_str(def_to_str(method_def_id).as_slice());
     ebml_w.end_tag();
     ebml_w.start_tag(tag_items_data_item_reexport_name);
-    ebml_w.wr_str(format!("{}::{}", exp.name, token::get_ident(method_ident)));
+    ebml_w.wr_str(format!("{}::{}",
+                          exp.name,
+                          token::get_ident(method_ident)));
     ebml_w.end_tag();
     ebml_w.end_tag();
 }
@@ -447,7 +449,7 @@ fn encode_reexported_static_methods(ecx: &EncodeContext,
             // encoded metadata for static methods relative to Bar,
             // but not yet for Foo.
             //
-            if path_differs || original_name.get() != exp.name {
+            if path_differs || original_name.get() != exp.name.as_slice() {
                 if !encode_reexported_static_base_methods(ecx, ebml_w, exp) {
                     if encode_reexported_static_trait_methods(ecx, ebml_w, exp) {
                         debug!("(encode reexported static methods) {} \
@@ -515,10 +517,10 @@ fn encode_reexports(ecx: &EncodeContext,
                        id);
                 ebml_w.start_tag(tag_items_data_item_reexport);
                 ebml_w.start_tag(tag_items_data_item_reexport_def_id);
-                ebml_w.wr_str(def_to_str(exp.def_id));
+                ebml_w.wr_str(def_to_str(exp.def_id).as_slice());
                 ebml_w.end_tag();
                 ebml_w.start_tag(tag_items_data_item_reexport_name);
-                ebml_w.wr_str(exp.name);
+                ebml_w.wr_str(exp.name.as_slice());
                 ebml_w.end_tag();
                 ebml_w.end_tag();
                 encode_reexported_static_methods(ecx, ebml_w, path.clone(), exp);
@@ -547,12 +549,13 @@ fn encode_info_for_mod(ecx: &EncodeContext,
     // Encode info about all the module children.
     for item in md.items.iter() {
         ebml_w.start_tag(tag_mod_child);
-        ebml_w.wr_str(def_to_str(local_def(item.id)));
+        ebml_w.wr_str(def_to_str(local_def(item.id)).as_slice());
         ebml_w.end_tag();
 
         each_auxiliary_node_id(*item, |auxiliary_node_id| {
             ebml_w.start_tag(tag_mod_child);
-            ebml_w.wr_str(def_to_str(local_def(auxiliary_node_id)));
+            ebml_w.wr_str(def_to_str(local_def(
+                        auxiliary_node_id)).as_slice());
             ebml_w.end_tag();
             true
         });
@@ -566,7 +569,7 @@ fn encode_info_for_mod(ecx: &EncodeContext,
                         did, ecx.tcx.map.node_to_str(did));
 
                 ebml_w.start_tag(tag_mod_impl);
-                ebml_w.wr_str(def_to_str(local_def(did)));
+                ebml_w.wr_str(def_to_str(local_def(did)).as_slice());
                 ebml_w.end_tag();
             }
             _ => {}
@@ -931,7 +934,7 @@ fn encode_info_for_item(ecx: &EncodeContext,
         // Encode all the items in this module.
         for foreign_item in fm.items.iter() {
             ebml_w.start_tag(tag_mod_child);
-            ebml_w.wr_str(def_to_str(local_def(foreign_item.id)));
+            ebml_w.wr_str(def_to_str(local_def(foreign_item.id)).as_slice());
             ebml_w.end_tag();
         }
         encode_visibility(ebml_w, vis);
@@ -1111,7 +1114,7 @@ fn encode_info_for_item(ecx: &EncodeContext,
             ebml_w.end_tag();
 
             ebml_w.start_tag(tag_mod_child);
-            ebml_w.wr_str(def_to_str(method_def_id));
+            ebml_w.wr_str(def_to_str(method_def_id).as_slice());
             ebml_w.end_tag();
         }
         encode_path(ebml_w, path.clone());
@@ -1647,12 +1650,13 @@ fn encode_misc_info(ecx: &EncodeContext,
     ebml_w.start_tag(tag_misc_info_crate_items);
     for &item in krate.module.items.iter() {
         ebml_w.start_tag(tag_mod_child);
-        ebml_w.wr_str(def_to_str(local_def(item.id)));
+        ebml_w.wr_str(def_to_str(local_def(item.id)).as_slice());
         ebml_w.end_tag();
 
         each_auxiliary_node_id(item, |auxiliary_node_id| {
             ebml_w.start_tag(tag_mod_child);
-            ebml_w.wr_str(def_to_str(local_def(auxiliary_node_id)));
+            ebml_w.wr_str(def_to_str(local_def(
+                        auxiliary_node_id)).as_slice());
             ebml_w.end_tag();
             true
         });
@@ -1700,11 +1704,11 @@ fn encode_dylib_dependency_formats(ebml_w: &mut Encoder, ecx: &EncodeContext) {
     match ecx.tcx.dependency_formats.borrow().find(&config::CrateTypeDylib) {
         Some(arr) => {
             let s = arr.iter().enumerate().filter_map(|(i, slot)| {
-                slot.map(|kind| format!("{}:{}", i + 1, match kind {
+                slot.map(|kind| (format!("{}:{}", i + 1, match kind {
                     cstore::RequireDynamic => "d",
                     cstore::RequireStatic => "s",
-                }))
-            }).collect::<Vec<~str>>();
+                })).to_strbuf())
+            }).collect::<Vec<StrBuf>>();
             ebml_w.writer.write(s.connect(",").as_bytes());
         }
         None => {}
@@ -1781,7 +1785,12 @@ fn encode_metadata_inner(wr: &mut MemWriter, parms: EncodeParams, krate: &Crate)
     let mut ebml_w = writer::Encoder(wr);
 
     encode_crate_id(&mut ebml_w, &ecx.link_meta.crateid);
-    encode_crate_triple(&mut ebml_w, tcx.sess.targ_cfg.target_strs.target_triple);
+    encode_crate_triple(&mut ebml_w,
+                        tcx.sess
+                           .targ_cfg
+                           .target_strs
+                           .target_triple
+                           .as_slice());
     encode_hash(&mut ebml_w, &ecx.link_meta.crate_hash);
     encode_dylib_dependency_formats(&mut ebml_w, &ecx);
 
@@ -1861,7 +1870,7 @@ fn encode_metadata_inner(wr: &mut MemWriter, parms: EncodeParams, krate: &Crate)
 }
 
 // Get the encoded string for a type
-pub fn encoded_ty(tcx: &ty::ctxt, t: ty::t) -> ~str {
+pub fn encoded_ty(tcx: &ty::ctxt, t: ty::t) -> StrBuf {
     let mut wr = MemWriter::new();
     tyencode::enc_ty(&mut wr, &tyencode::ctxt {
         diag: tcx.sess.diagnostic(),
@@ -1869,5 +1878,5 @@ pub fn encoded_ty(tcx: &ty::ctxt, t: ty::t) -> ~str {
         tcx: tcx,
         abbrevs: &RefCell::new(HashMap::new())
     }, t);
-    str::from_utf8_owned(wr.get_ref().to_owned()).unwrap()
+    str::from_utf8_owned(wr.get_ref().to_owned()).unwrap().to_strbuf()
 }
diff --git a/src/librustc/metadata/filesearch.rs b/src/librustc/metadata/filesearch.rs
index ec95ef5db6529..f339c6c8f7410 100644
--- a/src/librustc/metadata/filesearch.rs
+++ b/src/librustc/metadata/filesearch.rs
@@ -186,8 +186,8 @@ static PATH_ENTRY_SEPARATOR: &'static str = ";";
 static PATH_ENTRY_SEPARATOR: &'static str = ":";
 
 /// Returns RUST_PATH as a string, without default paths added
-pub fn get_rust_path() -> Option<~str> {
-    os::getenv("RUST_PATH")
+pub fn get_rust_path() -> Option<StrBuf> {
+    os::getenv("RUST_PATH").map(|x| x.to_strbuf())
 }
 
 /// Returns the value of RUST_PATH, as a list
@@ -199,7 +199,7 @@ pub fn rust_path() -> Vec<Path> {
     let mut env_rust_path: Vec<Path> = match get_rust_path() {
         Some(env_path) => {
             let env_path_components =
-                env_path.split_str(PATH_ENTRY_SEPARATOR);
+                env_path.as_slice().split_str(PATH_ENTRY_SEPARATOR);
             env_path_components.map(|s| Path::new(s)).collect()
         }
         None => Vec::new()
@@ -236,7 +236,7 @@ pub fn rust_path() -> Vec<Path> {
 // The name of the directory rustc expects libraries to be located.
 // On Unix should be "lib", on windows "bin"
 #[cfg(unix)]
-fn find_libdir(sysroot: &Path) -> ~str {
+fn find_libdir(sysroot: &Path) -> StrBuf {
     // FIXME: This is a quick hack to make the rustc binary able to locate
     // Rust libraries in Linux environments where libraries might be installed
     // to lib64/lib32. This would be more foolproof by basing the sysroot off
@@ -250,21 +250,27 @@ fn find_libdir(sysroot: &Path) -> ~str {
     }
 
     #[cfg(target_word_size = "64")]
-    fn primary_libdir_name() -> ~str { "lib64".to_owned() }
+    fn primary_libdir_name() -> StrBuf {
+        "lib64".to_strbuf()
+    }
 
     #[cfg(target_word_size = "32")]
-    fn primary_libdir_name() -> ~str { "lib32".to_owned() }
+    fn primary_libdir_name() -> StrBuf {
+        "lib32".to_strbuf()
+    }
 
-    fn secondary_libdir_name() -> ~str { "lib".to_owned() }
+    fn secondary_libdir_name() -> StrBuf {
+        "lib".to_strbuf()
+    }
 }
 
 #[cfg(windows)]
-fn find_libdir(_sysroot: &Path) -> ~str {
-    "bin".to_owned()
+fn find_libdir(_sysroot: &Path) -> StrBuf {
+    "bin".to_strbuf()
 }
 
 // The name of rustc's own place to organize libraries.
 // Used to be "rustc", now the default is "rustlib"
-pub fn rustlibdir() -> ~str {
-    "rustlib".to_owned()
+pub fn rustlibdir() -> StrBuf {
+    "rustlib".to_strbuf()
 }
diff --git a/src/librustc/metadata/loader.rs b/src/librustc/metadata/loader.rs
index c872df3deade9..456259d1a5d04 100644
--- a/src/librustc/metadata/loader.rs
+++ b/src/librustc/metadata/loader.rs
@@ -61,7 +61,7 @@ pub enum Os {
 
 pub struct CrateMismatch {
     path: Path,
-    got: ~str,
+    got: StrBuf,
 }
 
 pub struct Context<'a> {
@@ -92,7 +92,7 @@ pub struct ArchiveMetadata {
 }
 
 pub struct CratePaths {
-    pub ident: ~str,
+    pub ident: StrBuf,
     pub dylib: Option<Path>,
     pub rlib: Option<Path>
 }
@@ -305,7 +305,7 @@ impl<'a> Context<'a> {
     //
     // If everything checks out, then `Some(hash)` is returned where `hash` is
     // the listed hash in the filename itself.
-    fn try_match(&self, file: &str, prefix: &str, suffix: &str) -> Option<~str>{
+    fn try_match(&self, file: &str, prefix: &str, suffix: &str) -> Option<StrBuf>{
         let middle = file.slice(prefix.len(), file.len() - suffix.len());
         debug!("matching -- {}, middle: {}", file, middle);
         let mut parts = middle.splitn('-', 1);
@@ -319,13 +319,13 @@ impl<'a> Context<'a> {
             Some(..) => {} // check the hash
 
             // hash is irrelevant, no version specified
-            None => return Some(hash.to_owned())
+            None => return Some(hash.to_strbuf())
         }
         debug!("matching -- {}, vers ok", file);
         // hashes in filenames are prefixes of the "true hash"
         if self.id_hash == hash.as_slice() {
             debug!("matching -- {}, hash ok", file);
-            Some(hash.to_owned())
+            Some(hash.to_strbuf())
         } else {
             None
         }
@@ -410,8 +410,10 @@ impl<'a> Context<'a> {
         let triple = decoder::get_crate_triple(crate_data);
         if triple.as_slice() != self.triple {
             info!("Rejecting via crate triple: expected {} got {}", self.triple, triple);
-            self.rejected_via_triple.push(CrateMismatch{ path: libpath.clone(),
-                                                         got: triple.to_owned() });
+            self.rejected_via_triple.push(CrateMismatch {
+                path: libpath.clone(),
+                got: triple.to_strbuf()
+            });
             return false;
         }
 
@@ -420,8 +422,10 @@ impl<'a> Context<'a> {
             Some(myhash) => {
                 if *myhash != hash {
                     info!("Rejecting via hash: expected {} got {}", *myhash, hash);
-                    self.rejected_via_hash.push(CrateMismatch{ path: libpath.clone(),
-                                                               got: myhash.as_str().to_owned() });
+                    self.rejected_via_hash.push(CrateMismatch {
+                        path: libpath.clone(),
+                        got: myhash.as_str().to_strbuf()
+                    });
                     false
                 } else {
                     true
@@ -481,7 +485,7 @@ impl ArchiveMetadata {
 }
 
 // Just a small wrapper to time how long reading metadata takes.
-fn get_metadata_section(os: Os, filename: &Path) -> Result<MetadataBlob, ~str> {
+fn get_metadata_section(os: Os, filename: &Path) -> Result<MetadataBlob, StrBuf> {
     let start = time::precise_time_ns();
     let ret = get_metadata_section_imp(os, filename);
     info!("reading {} => {}ms", filename.filename_display(),
@@ -489,9 +493,9 @@ fn get_metadata_section(os: Os, filename: &Path) -> Result<MetadataBlob, ~str> {
     return ret;
 }
 
-fn get_metadata_section_imp(os: Os, filename: &Path) -> Result<MetadataBlob, ~str> {
+fn get_metadata_section_imp(os: Os, filename: &Path) -> Result<MetadataBlob, StrBuf> {
     if !filename.exists() {
-        return Err(format!("no such file: '{}'", filename.display()));
+        return Err(format_strbuf!("no such file: '{}'", filename.display()));
     }
     if filename.filename_str().unwrap().ends_with(".rlib") {
         // Use ArchiveRO for speed here, it's backed by LLVM and uses mmap
@@ -501,13 +505,17 @@ fn get_metadata_section_imp(os: Os, filename: &Path) -> Result<MetadataBlob, ~st
             Some(ar) => ar,
             None => {
                 debug!("llvm didn't like `{}`", filename.display());
-                return Err(format!("failed to read rlib metadata: '{}'",
-                                   filename.display()));
+                return Err(format_strbuf!("failed to read rlib metadata: \
+                                           '{}'",
+                                          filename.display()));
             }
         };
         return match ArchiveMetadata::new(archive).map(|ar| MetadataArchive(ar)) {
-            None => return Err(format!("failed to read rlib metadata: '{}'",
-                                       filename.display())),
+            None => {
+                return Err((format_strbuf!("failed to read rlib metadata: \
+                                            '{}'",
+                                           filename.display())))
+            }
             Some(blob) => return Ok(blob)
         }
     }
@@ -516,11 +524,16 @@ fn get_metadata_section_imp(os: Os, filename: &Path) -> Result<MetadataBlob, ~st
             llvm::LLVMRustCreateMemoryBufferWithContentsOfFile(buf)
         });
         if mb as int == 0 {
-            return Err(format!("error reading library: '{}'",filename.display()))
+            return Err(format_strbuf!("error reading library: '{}'",
+                                      filename.display()))
         }
         let of = match ObjectFile::new(mb) {
             Some(of) => of,
-            _ => return Err(format!("provided path not an object file: '{}'", filename.display()))
+            _ => {
+                return Err((format_strbuf!("provided path not an object \
+                                            file: '{}'",
+                                           filename.display())))
+            }
         };
         let si = mk_section_iter(of.llof);
         while llvm::LLVMIsSectionIteratorAtEnd(of.llof, si.llsi) == False {
@@ -531,7 +544,9 @@ fn get_metadata_section_imp(os: Os, filename: &Path) -> Result<MetadataBlob, ~st
             if read_meta_section_name(os) == name {
                 let cbuf = llvm::LLVMGetSectionContents(si.llsi);
                 let csz = llvm::LLVMGetSectionSize(si.llsi) as uint;
-                let mut found = Err(format!("metadata not found: '{}'", filename.display()));
+                let mut found =
+                    Err(format_strbuf!("metadata not found: '{}'",
+                                       filename.display()));
                 let cvbuf: *u8 = mem::transmute(cbuf);
                 let vlen = encoder::metadata_encoding_version.len();
                 debug!("checking {} bytes of metadata-version stamp",
@@ -539,8 +554,11 @@ fn get_metadata_section_imp(os: Os, filename: &Path) -> Result<MetadataBlob, ~st
                 let minsz = cmp::min(vlen, csz);
                 let version_ok = slice::raw::buf_as_slice(cvbuf, minsz,
                     |buf0| buf0 == encoder::metadata_encoding_version);
-                if !version_ok { return Err(format!("incompatible metadata version found: '{}'",
-                                                    filename.display())); }
+                if !version_ok {
+                    return Err((format_strbuf!("incompatible metadata \
+                                                version found: '{}'",
+                                        filename.display())));
+                }
 
                 let cvbuf1 = cvbuf.offset(vlen as int);
                 debug!("inflating {} bytes of compressed metadata",
@@ -548,8 +566,12 @@ fn get_metadata_section_imp(os: Os, filename: &Path) -> Result<MetadataBlob, ~st
                 slice::raw::buf_as_slice(cvbuf1, csz-vlen, |bytes| {
                     match flate::inflate_bytes(bytes) {
                         Some(inflated) => found = Ok(MetadataVec(inflated)),
-                        None => found = Err(format!("failed to decompress metadata for: '{}'",
-                                                    filename.display()))
+                        None => {
+                            found =
+                                Err(format_strbuf!("failed to decompress \
+                                                    metadata for: '{}'",
+                                                   filename.display()))
+                        }
                     }
                 });
                 if found.is_ok() {
@@ -558,7 +580,8 @@ fn get_metadata_section_imp(os: Os, filename: &Path) -> Result<MetadataBlob, ~st
             }
             llvm::LLVMMoveToNextSection(si.llsi);
         }
-        return Err(format!("metadata not found: '{}'", filename.display()));
+        return Err(format_strbuf!("metadata not found: '{}'",
+                                  filename.display()));
     }
 }
 
diff --git a/src/librustc/metadata/tydecode.rs b/src/librustc/metadata/tydecode.rs
index 76621cfd09f84..0ccb44d2f8cae 100644
--- a/src/librustc/metadata/tydecode.rs
+++ b/src/librustc/metadata/tydecode.rs
@@ -201,7 +201,7 @@ fn parse_bound_region(st: &mut PState, conv: conv_did) -> ty::BoundRegion {
         }
         '[' => {
             let def = parse_def(st, RegionParameter, |x,y| conv(x,y));
-            let ident = token::str_to_ident(parse_str(st, ']'));
+            let ident = token::str_to_ident(parse_str(st, ']').as_slice());
             ty::BrNamed(def, ident.name)
         }
         'f' => {
@@ -229,7 +229,7 @@ fn parse_region(st: &mut PState, conv: conv_did) -> ty::Region {
         assert_eq!(next(st), '|');
         let index = parse_uint(st);
         assert_eq!(next(st), '|');
-        let nm = token::str_to_ident(parse_str(st, ']'));
+        let nm = token::str_to_ident(parse_str(st, ']').as_slice());
         ty::ReEarlyBound(node_id, index, nm.name)
       }
       'f' => {
@@ -264,7 +264,7 @@ fn parse_opt<T>(st: &mut PState, f: |&mut PState| -> T) -> Option<T> {
     }
 }
 
-fn parse_str(st: &mut PState, term: char) -> ~str {
+fn parse_str(st: &mut PState, term: char) -> StrBuf {
     let mut result = StrBuf::new();
     while peek(st) != term {
         unsafe {
@@ -272,7 +272,7 @@ fn parse_str(st: &mut PState, term: char) -> ~str {
         }
     }
     next(st);
-    return result.into_owned();
+    result
 }
 
 fn parse_trait_ref(st: &mut PState, conv: conv_did) -> ty::TraitRef {
diff --git a/src/librustc/metadata/tyencode.rs b/src/librustc/metadata/tyencode.rs
index fd41d219b417a..49b5d7b28640c 100644
--- a/src/librustc/metadata/tyencode.rs
+++ b/src/librustc/metadata/tyencode.rs
@@ -35,7 +35,7 @@ macro_rules! mywrite( ($wr:expr, $($arg:tt)*) => (
 pub struct ctxt<'a> {
     pub diag: &'a SpanHandler,
     // Def -> str Callback:
-    pub ds: fn(DefId) -> ~str,
+    pub ds: fn(DefId) -> StrBuf,
     // The type context.
     pub tcx: &'a ty::ctxt,
     pub abbrevs: &'a abbrev_map
@@ -47,7 +47,7 @@ pub struct ctxt<'a> {
 pub struct ty_abbrev {
     pos: uint,
     len: uint,
-    s: ~str
+    s: StrBuf
 }
 
 pub type abbrev_map = RefCell<HashMap<ty::t, ty_abbrev>>;
@@ -77,7 +77,7 @@ pub fn enc_ty(w: &mut MemWriter, cx: &ctxt, t: ty::t) {
         cx.abbrevs.borrow_mut().insert(t, ty_abbrev {
             pos: pos as uint,
             len: len as uint,
-            s: format!("\\#{:x}:{:x}\\#", pos, len)
+            s: format_strbuf!("\\#{:x}:{:x}\\#", pos, len)
         });
     }
 }
diff --git a/src/librustc/middle/astencode.rs b/src/librustc/middle/astencode.rs
index ae1a12901049d..f46fe9a8b2491 100644
--- a/src/librustc/middle/astencode.rs
+++ b/src/librustc/middle/astencode.rs
@@ -1152,12 +1152,12 @@ impl<'a> ebml_decoder_decoder_helpers for reader::Decoder<'a> {
             Ok(ty)
         }).unwrap();
 
-        fn type_string(doc: ebml::Doc) -> ~str {
+        fn type_string(doc: ebml::Doc) -> StrBuf {
             let mut str = StrBuf::new();
             for i in range(doc.start, doc.end) {
                 str.push_char(doc.data[i] as char);
             }
-            str.into_owned()
+            str
         }
     }
 
diff --git a/src/librustc/middle/borrowck/mod.rs b/src/librustc/middle/borrowck/mod.rs
index 96d0d0eaa2ff0..ad0ee14373565 100644
--- a/src/librustc/middle/borrowck/mod.rs
+++ b/src/librustc/middle/borrowck/mod.rs
@@ -98,10 +98,10 @@ pub fn check_crate(tcx: &ty::ctxt,
                  make_stat(&bccx, bccx.stats.stable_paths.get()));
     }
 
-    fn make_stat(bccx: &BorrowckCtxt, stat: uint) -> ~str {
+    fn make_stat(bccx: &BorrowckCtxt, stat: uint) -> StrBuf {
         let stat_f = stat as f64;
         let total = bccx.stats.guaranteed_paths.get() as f64;
-        format!("{} ({:.0f}%)", stat  , stat_f * 100.0 / total)
+        format_strbuf!("{} ({:.0f}%)", stat  , stat_f * 100.0 / total)
     }
 }
 
@@ -303,8 +303,8 @@ impl BitAnd<RestrictionSet,RestrictionSet> for RestrictionSet {
 }
 
 impl Repr for RestrictionSet {
-    fn repr(&self, _tcx: &ty::ctxt) -> ~str {
-        format!("RestrictionSet(0x{:x})", self.bits as uint)
+    fn repr(&self, _tcx: &ty::ctxt) -> StrBuf {
+        format_strbuf!("RestrictionSet(0x{:x})", self.bits as uint)
     }
 }
 
@@ -447,7 +447,7 @@ impl<'a> BorrowckCtxt<'a> {
     pub fn report(&self, err: BckError) {
         self.span_err(
             err.span,
-            self.bckerr_to_str(&err));
+            self.bckerr_to_str(&err).as_slice());
         self.note_and_explain_bckerr(err);
     }
 
@@ -572,28 +572,32 @@ impl<'a> BorrowckCtxt<'a> {
         self.tcx.sess.span_end_note(s, m);
     }
 
-    pub fn bckerr_to_str(&self, err: &BckError) -> ~str {
+    pub fn bckerr_to_str(&self, err: &BckError) -> StrBuf {
         match err.code {
             err_mutbl => {
                 let descr = match opt_loan_path(&err.cmt) {
-                    None => format!("{} {}",
-                                    err.cmt.mutbl.to_user_str(),
-                                    self.cmt_to_str(&*err.cmt)),
-                    Some(lp) => format!("{} {} `{}`",
-                                        err.cmt.mutbl.to_user_str(),
-                                        self.cmt_to_str(&*err.cmt),
-                                        self.loan_path_to_str(&*lp)),
+                    None => {
+                        format_strbuf!("{} {}",
+                                       err.cmt.mutbl.to_user_str(),
+                                       self.cmt_to_str(&*err.cmt))
+                    }
+                    Some(lp) => {
+                        format_strbuf!("{} {} `{}`",
+                                       err.cmt.mutbl.to_user_str(),
+                                       self.cmt_to_str(&*err.cmt),
+                                       self.loan_path_to_str(&*lp))
+                    }
                 };
 
                 match err.cause {
                     euv::ClosureCapture(_) => {
-                        format!("closure cannot assign to {}", descr)
+                        format_strbuf!("closure cannot assign to {}", descr)
                     }
                     euv::OverloadedOperator |
                     euv::AddrOf |
                     euv::RefBinding |
                     euv::AutoRef => {
-                        format!("cannot borrow {} as mutable", descr)
+                        format_strbuf!("cannot borrow {} as mutable", descr)
                     }
                     euv::ClosureInvocation => {
                         self.tcx.sess.span_bug(err.span,
@@ -603,20 +607,24 @@ impl<'a> BorrowckCtxt<'a> {
             }
             err_out_of_scope(..) => {
                 let msg = match opt_loan_path(&err.cmt) {
-                    None => format!("borrowed value"),
-                    Some(lp) => format!("`{}`", self.loan_path_to_str(&*lp)),
+                    None => "borrowed value".to_strbuf(),
+                    Some(lp) => {
+                        format_strbuf!("`{}`", self.loan_path_to_str(&*lp))
+                    }
                 };
-                format!("{} does not live long enough", msg)
+                format_strbuf!("{} does not live long enough", msg)
             }
             err_borrowed_pointer_too_short(..) => {
                 let descr = match opt_loan_path(&err.cmt) {
-                    Some(lp) => format!("`{}`", self.loan_path_to_str(&*lp)),
+                    Some(lp) => {
+                        format_strbuf!("`{}`", self.loan_path_to_str(&*lp))
+                    }
                     None => self.cmt_to_str(&*err.cmt),
                 };
 
-                format!("lifetime of {} is too short to guarantee \
-                        its contents can be safely reborrowed",
-                        descr)
+                format_strbuf!("lifetime of {} is too short to guarantee \
+                                its contents can be safely reborrowed",
+                               descr)
             }
         }
     }
@@ -655,7 +663,8 @@ impl<'a> BorrowckCtxt<'a> {
             mc::AliasableOther => {
                 self.tcx.sess.span_err(
                     span,
-                    format!("{} in an aliasable location", prefix));
+                    format!("{} in an aliasable location",
+                             prefix));
             }
             mc::AliasableStatic(..) |
             mc::AliasableStaticMut(..) => {
@@ -696,7 +705,9 @@ impl<'a> BorrowckCtxt<'a> {
 
             err_borrowed_pointer_too_short(loan_scope, ptr_scope, _) => {
                 let descr = match opt_loan_path(&err.cmt) {
-                    Some(lp) => format!("`{}`", self.loan_path_to_str(&*lp)),
+                    Some(lp) => {
+                        format_strbuf!("`{}`", self.loan_path_to_str(&*lp))
+                    }
                     None => self.cmt_to_str(&*err.cmt),
                 };
                 note_and_explain_region(
@@ -764,13 +775,13 @@ impl<'a> BorrowckCtxt<'a> {
         }
     }
 
-    pub fn loan_path_to_str(&self, loan_path: &LoanPath) -> ~str {
+    pub fn loan_path_to_str(&self, loan_path: &LoanPath) -> StrBuf {
         let mut result = StrBuf::new();
         self.append_loan_path_to_str(loan_path, &mut result);
-        result.into_owned()
+        result
     }
 
-    pub fn cmt_to_str(&self, cmt: &mc::cmt_) -> ~str {
+    pub fn cmt_to_str(&self, cmt: &mc::cmt_) -> StrBuf {
         self.mc().cmt_to_str(cmt)
     }
 }
@@ -788,38 +799,40 @@ impl DataFlowOperator for LoanDataFlowOperator {
 }
 
 impl Repr for Loan {
-    fn repr(&self, tcx: &ty::ctxt) -> ~str {
-        format!("Loan_{:?}({}, {:?}, {:?}-{:?}, {})",
-             self.index,
-             self.loan_path.repr(tcx),
-             self.kind,
-             self.gen_scope,
-             self.kill_scope,
-             self.restrictions.repr(tcx))
+    fn repr(&self, tcx: &ty::ctxt) -> StrBuf {
+        (format!("Loan_{:?}({}, {:?}, {:?}-{:?}, {})",
+                 self.index,
+                 self.loan_path.repr(tcx),
+                 self.kind,
+                 self.gen_scope,
+                 self.kill_scope,
+                 self.restrictions.repr(tcx))).to_strbuf()
     }
 }
 
 impl Repr for Restriction {
-    fn repr(&self, tcx: &ty::ctxt) -> ~str {
-        format!("Restriction({}, {:x})",
-             self.loan_path.repr(tcx),
-             self.set.bits as uint)
+    fn repr(&self, tcx: &ty::ctxt) -> StrBuf {
+        (format!("Restriction({}, {:x})",
+                 self.loan_path.repr(tcx),
+                 self.set.bits as uint)).to_strbuf()
     }
 }
 
 impl Repr for LoanPath {
-    fn repr(&self, tcx: &ty::ctxt) -> ~str {
+    fn repr(&self, tcx: &ty::ctxt) -> StrBuf {
         match self {
             &LpVar(id) => {
-                format!("$({})", tcx.map.node_to_str(id))
+                (format!("$({})", tcx.map.node_to_str(id))).to_strbuf()
             }
 
             &LpExtend(ref lp, _, LpDeref(_)) => {
-                format!("{}.*", lp.repr(tcx))
+                (format!("{}.*", lp.repr(tcx))).to_strbuf()
             }
 
             &LpExtend(ref lp, _, LpInterior(ref interior)) => {
-                format!("{}.{}", lp.repr(tcx), interior.repr(tcx))
+                (format!("{}.{}",
+                         lp.repr(tcx),
+                         interior.repr(tcx))).to_strbuf()
             }
         }
     }
diff --git a/src/librustc/middle/check_const.rs b/src/librustc/middle/check_const.rs
index eb52aa18de85f..f5f551e36f7ba 100644
--- a/src/librustc/middle/check_const.rs
+++ b/src/librustc/middle/check_const.rs
@@ -102,9 +102,12 @@ fn check_expr(v: &mut CheckCrateVisitor, e: &Expr, is_const: bool) {
           ExprCast(_, _) => {
             let ety = ty::expr_ty(v.tcx, e);
             if !ty::type_is_numeric(ety) && !ty::type_is_unsafe_ptr(ety) {
-                v.tcx.sess.span_err(e.span, "can not cast to `".to_owned() +
-                                              ppaux::ty_to_str(v.tcx, ety) +
-                                             "` in a constant expression");
+                v.tcx
+                 .sess
+                 .span_err(e.span,
+                           format!("can not cast to `{}` in a constant \
+                                    expression",
+                                   ppaux::ty_to_str(v.tcx, ety).as_slice()))
             }
           }
           ExprPath(ref pth) => {
diff --git a/src/librustc/middle/check_static.rs b/src/librustc/middle/check_static.rs
index 763c1abdc7394..b24933a8c01a0 100644
--- a/src/librustc/middle/check_static.rs
+++ b/src/librustc/middle/check_static.rs
@@ -33,7 +33,7 @@ use syntax::visit;
 use syntax::print::pprust;
 
 
-fn safe_type_for_static_mut(cx: &ty::ctxt, e: &ast::Expr) -> Option<~str> {
+fn safe_type_for_static_mut(cx: &ty::ctxt, e: &ast::Expr) -> Option<StrBuf> {
     let node_ty = ty::node_id_to_type(cx, e.id);
     let tcontents = ty::type_contents(cx, node_ty);
     debug!("safe_type_for_static_mut(dtor={}, managed={}, owned={})",
@@ -49,7 +49,8 @@ fn safe_type_for_static_mut(cx: &ty::ctxt, e: &ast::Expr) -> Option<~str> {
         return None;
     };
 
-    Some(format!("mutable static items are not allowed to have {}", suffix))
+    Some(format_strbuf!("mutable static items are not allowed to have {}",
+                        suffix))
 }
 
 struct CheckStaticVisitor<'a> {
@@ -61,11 +62,11 @@ pub fn check_crate(tcx: &ty::ctxt, krate: &ast::Crate) {
 }
 
 impl<'a> CheckStaticVisitor<'a> {
-    fn report_error(&self, span: Span, result: Option<~str>) -> bool {
+    fn report_error(&self, span: Span, result: Option<StrBuf>) -> bool {
         match result {
             None => { false }
             Some(msg) => {
-                self.tcx.sess.span_err(span, msg);
+                self.tcx.sess.span_err(span, msg.as_slice());
                 true
             }
         }
@@ -132,7 +133,8 @@ impl<'a> Visitor<bool> for CheckStaticVisitor<'a> {
                     ty::ty_enum(did, _) => {
                         if ty::has_dtor(self.tcx, did) {
                             self.report_error(e.span,
-                             Some("static items are not allowed to have destructors".to_owned()));
+                             Some("static items are not allowed to have \
+                                   destructors".to_strbuf()));
                             return;
                         }
                     }
diff --git a/src/librustc/middle/const_eval.rs b/src/librustc/middle/const_eval.rs
index 7f083865d141b..34f36363b92bf 100644
--- a/src/librustc/middle/const_eval.rs
+++ b/src/librustc/middle/const_eval.rs
@@ -295,21 +295,21 @@ pub enum const_val {
 pub fn eval_const_expr(tcx: &ty::ctxt, e: &Expr) -> const_val {
     match eval_const_expr_partial(tcx, e) {
         Ok(r) => r,
-        Err(s) => tcx.sess.span_fatal(e.span, s)
+        Err(s) => tcx.sess.span_fatal(e.span, s.as_slice())
     }
 }
 
 pub fn eval_const_expr_partial<T: ty::ExprTyProvider>(tcx: &T, e: &Expr)
-                            -> Result<const_val, ~str> {
-    fn fromb(b: bool) -> Result<const_val, ~str> { Ok(const_int(b as i64)) }
+                            -> Result<const_val, StrBuf> {
+    fn fromb(b: bool) -> Result<const_val, StrBuf> { Ok(const_int(b as i64)) }
     match e.node {
       ExprUnary(UnNeg, inner) => {
         match eval_const_expr_partial(tcx, inner) {
           Ok(const_float(f)) => Ok(const_float(-f)),
           Ok(const_int(i)) => Ok(const_int(-i)),
           Ok(const_uint(i)) => Ok(const_uint(-i)),
-          Ok(const_str(_)) => Err("negate on string".to_owned()),
-          Ok(const_bool(_)) => Err("negate on boolean".to_owned()),
+          Ok(const_str(_)) => Err("negate on string".to_strbuf()),
+          Ok(const_bool(_)) => Err("negate on boolean".to_strbuf()),
           ref err => ((*err).clone())
         }
       }
@@ -318,7 +318,7 @@ pub fn eval_const_expr_partial<T: ty::ExprTyProvider>(tcx: &T, e: &Expr)
           Ok(const_int(i)) => Ok(const_int(!i)),
           Ok(const_uint(i)) => Ok(const_uint(!i)),
           Ok(const_bool(b)) => Ok(const_bool(!b)),
-          _ => Err("not on float or string".to_owned())
+          _ => Err("not on float or string".to_strbuf())
         }
       }
       ExprBinary(op, a, b) => {
@@ -337,7 +337,7 @@ pub fn eval_const_expr_partial<T: ty::ExprTyProvider>(tcx: &T, e: &Expr)
               BiNe => fromb(a != b),
               BiGe => fromb(a >= b),
               BiGt => fromb(a > b),
-              _ => Err("can't do this op on floats".to_owned())
+              _ => Err("can't do this op on floats".to_strbuf())
             }
           }
           (Ok(const_int(a)), Ok(const_int(b))) => {
@@ -345,9 +345,14 @@ pub fn eval_const_expr_partial<T: ty::ExprTyProvider>(tcx: &T, e: &Expr)
               BiAdd => Ok(const_int(a + b)),
               BiSub => Ok(const_int(a - b)),
               BiMul => Ok(const_int(a * b)),
-              BiDiv if b == 0 => Err("attempted to divide by zero".to_owned()),
+              BiDiv if b == 0 => {
+                  Err("attempted to divide by zero".to_strbuf())
+              }
               BiDiv => Ok(const_int(a / b)),
-              BiRem if b == 0 => Err("attempted remainder with a divisor of zero".to_owned()),
+              BiRem if b == 0 => {
+                  Err("attempted remainder with a divisor of \
+                       zero".to_strbuf())
+              }
               BiRem => Ok(const_int(a % b)),
               BiAnd | BiBitAnd => Ok(const_int(a & b)),
               BiOr | BiBitOr => Ok(const_int(a | b)),
@@ -367,9 +372,14 @@ pub fn eval_const_expr_partial<T: ty::ExprTyProvider>(tcx: &T, e: &Expr)
               BiAdd => Ok(const_uint(a + b)),
               BiSub => Ok(const_uint(a - b)),
               BiMul => Ok(const_uint(a * b)),
-              BiDiv if b == 0 => Err("attempted to divide by zero".to_owned()),
+              BiDiv if b == 0 => {
+                  Err("attempted to divide by zero".to_strbuf())
+              }
               BiDiv => Ok(const_uint(a / b)),
-              BiRem if b == 0 => Err("attempted remainder with a divisor of zero".to_owned()),
+              BiRem if b == 0 => {
+                  Err("attempted remainder with a divisor of \
+                       zero".to_strbuf())
+              }
               BiRem => Ok(const_uint(a % b)),
               BiAnd | BiBitAnd => Ok(const_uint(a & b)),
               BiOr | BiBitOr => Ok(const_uint(a | b)),
@@ -389,14 +399,14 @@ pub fn eval_const_expr_partial<T: ty::ExprTyProvider>(tcx: &T, e: &Expr)
             match op {
               BiShl => Ok(const_int(a << b)),
               BiShr => Ok(const_int(a >> b)),
-              _ => Err("can't do this op on an int and uint".to_owned())
+              _ => Err("can't do this op on an int and uint".to_strbuf())
             }
           }
           (Ok(const_uint(a)), Ok(const_int(b))) => {
             match op {
               BiShl => Ok(const_uint(a << b)),
               BiShr => Ok(const_uint(a >> b)),
-              _ => Err("can't do this op on a uint and int".to_owned())
+              _ => Err("can't do this op on a uint and int".to_strbuf())
             }
           }
           (Ok(const_bool(a)), Ok(const_bool(b))) => {
@@ -408,10 +418,10 @@ pub fn eval_const_expr_partial<T: ty::ExprTyProvider>(tcx: &T, e: &Expr)
               BiBitOr => a | b,
               BiEq => a == b,
               BiNe => a != b,
-              _ => return Err("can't do this op on bools".to_owned())
+              _ => return Err("can't do this op on bools".to_strbuf())
              }))
           }
-          _ => Err("bad operands for binary".to_owned())
+          _ => Err("bad operands for binary".to_strbuf())
         }
       }
       ExprCast(base, target_ty) => {
@@ -435,7 +445,7 @@ pub fn eval_const_expr_partial<T: ty::ExprTyProvider>(tcx: &T, e: &Expr)
                             const_uint(u) => Ok(const_float(u as f64)),
                             const_int(i) => Ok(const_float(i as f64)),
                             const_float(f) => Ok(const_float(f)),
-                            _ => Err("can't cast float to str".to_owned()),
+                            _ => Err("can't cast float to str".to_strbuf()),
                         }
                     }
                     ty::ty_uint(_) => {
@@ -443,7 +453,7 @@ pub fn eval_const_expr_partial<T: ty::ExprTyProvider>(tcx: &T, e: &Expr)
                             const_uint(u) => Ok(const_uint(u)),
                             const_int(i) => Ok(const_uint(i as u64)),
                             const_float(f) => Ok(const_uint(f as u64)),
-                            _ => Err("can't cast str to uint".to_owned()),
+                            _ => Err("can't cast str to uint".to_strbuf()),
                         }
                     }
                     ty::ty_int(_) | ty::ty_bool => {
@@ -451,10 +461,10 @@ pub fn eval_const_expr_partial<T: ty::ExprTyProvider>(tcx: &T, e: &Expr)
                             const_uint(u) => Ok(const_int(u as i64)),
                             const_int(i) => Ok(const_int(i)),
                             const_float(f) => Ok(const_int(f as i64)),
-                            _ => Err("can't cast str to int".to_owned()),
+                            _ => Err("can't cast str to int".to_strbuf()),
                         }
                     }
-                    _ => Err("can't cast this type".to_owned())
+                    _ => Err("can't cast this type".to_strbuf())
                 }
             }
         }
@@ -462,14 +472,14 @@ pub fn eval_const_expr_partial<T: ty::ExprTyProvider>(tcx: &T, e: &Expr)
       ExprPath(_) => {
           match lookup_const(tcx.ty_ctxt(), e) {
               Some(actual_e) => eval_const_expr_partial(tcx.ty_ctxt(), actual_e),
-              None => Err("non-constant path in constant expr".to_owned())
+              None => Err("non-constant path in constant expr".to_strbuf())
           }
       }
       ExprLit(lit) => Ok(lit_to_const(lit)),
       // If we have a vstore, just keep going; it has to be a string
       ExprVstore(e, _) => eval_const_expr_partial(tcx, e),
       ExprParen(e)     => eval_const_expr_partial(tcx, e),
-      _ => Err("unsupported constant expr".to_owned())
+      _ => Err("unsupported constant expr".to_strbuf())
     }
 }
 
diff --git a/src/librustc/middle/dataflow.rs b/src/librustc/middle/dataflow.rs
index 48c6d2a53d756..34a97c15f5c45 100644
--- a/src/librustc/middle/dataflow.rs
+++ b/src/librustc/middle/dataflow.rs
@@ -112,8 +112,11 @@ impl<'a, O:DataFlowOperator> pprust::PpAnn for DataFlowContext<'a, O> {
                 "".to_owned()
             };
 
-            try!(ps.synth_comment((format!("id {}: {}{}{}", id, entry_str,
-                                          gens_str, kills_str)).to_strbuf()));
+            try!(ps.synth_comment(format_strbuf!("id {}: {}{}{}",
+                                                 id,
+                                                 entry_str,
+                                                 gens_str,
+                                                 kills_str)));
             try!(pp::space(&mut ps.s));
         }
         Ok(())
@@ -824,11 +827,11 @@ impl<'a, 'b, O:DataFlowOperator> PropagationContext<'a, 'b, O> {
     }
 }
 
-fn mut_bits_to_str(words: &mut [uint]) -> ~str {
+fn mut_bits_to_str(words: &mut [uint]) -> StrBuf {
     bits_to_str(words)
 }
 
-fn bits_to_str(words: &[uint]) -> ~str {
+fn bits_to_str(words: &[uint]) -> StrBuf {
     let mut result = StrBuf::new();
     let mut sep = '[';
 
@@ -844,7 +847,7 @@ fn bits_to_str(words: &[uint]) -> ~str {
         }
     }
     result.push_char(']');
-    return result.into_owned();
+    return result
 }
 
 fn copy_bits(in_vec: &[uint], out_vec: &mut [uint]) -> bool {
@@ -884,8 +887,8 @@ fn set_bit(words: &mut [uint], bit: uint) -> bool {
     oldv != newv
 }
 
-fn bit_str(bit: uint) -> ~str {
+fn bit_str(bit: uint) -> StrBuf {
     let byte = bit >> 8;
     let lobits = 1 << (bit & 0xFF);
-    format!("[{}:{}-{:02x}]", bit, byte, lobits)
+    format_strbuf!("[{}:{}-{:02x}]", bit, byte, lobits)
 }
diff --git a/src/librustc/middle/dead.rs b/src/librustc/middle/dead.rs
index f3a8b9d20d5f7..407228cb6ede8 100644
--- a/src/librustc/middle/dead.rs
+++ b/src/librustc/middle/dead.rs
@@ -352,11 +352,17 @@ impl<'a> DeadVisitor<'a> {
         false
     }
 
-    fn warn_dead_code(&mut self, id: ast::NodeId,
-                      span: codemap::Span, ident: ast::Ident) {
-        self.tcx.sess.add_lint(DeadCode, id, span,
-                               format!("code is never used: `{}`",
-                                       token::get_ident(ident)));
+    fn warn_dead_code(&mut self,
+                      id: ast::NodeId,
+                      span: codemap::Span,
+                      ident: ast::Ident) {
+        self.tcx
+            .sess
+            .add_lint(DeadCode,
+                      id,
+                      span,
+                      format_strbuf!("code is never used: `{}`",
+                                     token::get_ident(ident)));
     }
 }
 
diff --git a/src/librustc/middle/kind.rs b/src/librustc/middle/kind.rs
index b88083c0df9ab..2604884350b90 100644
--- a/src/librustc/middle/kind.rs
+++ b/src/librustc/middle/kind.rs
@@ -562,7 +562,7 @@ pub fn check_cast_for_escaping_regions(
 }
 
 // Ensure that `ty` has a statically known size (i.e., it has the `Sized` bound).
-fn check_sized(tcx: &ty::ctxt, ty: ty::t, name: ~str, sp: Span) {
+fn check_sized(tcx: &ty::ctxt, ty: ty::t, name: StrBuf, sp: Span) {
     if !ty::type_is_sized(tcx, ty) {
         tcx.sess.span_err(sp, format!("variable `{}` has dynamically sized type `{}`",
                                       name, ty_to_str(tcx, ty)));
@@ -572,8 +572,8 @@ fn check_sized(tcx: &ty::ctxt, ty: ty::t, name: ~str, sp: Span) {
 // Check that any variables in a pattern have types with statically known size.
 fn check_pat(cx: &mut Context, pat: &Pat) {
     let var_name = match pat.node {
-        PatWild => Some("_".to_owned()),
-        PatIdent(_, ref path, _) => Some(path_to_str(path).to_owned()),
+        PatWild => Some("_".to_strbuf()),
+        PatIdent(_, ref path, _) => Some(path_to_str(path).to_strbuf()),
         _ => None
     };
 
diff --git a/src/librustc/middle/lang_items.rs b/src/librustc/middle/lang_items.rs
index 48465309f1ed5..ed8b27a866026 100644
--- a/src/librustc/middle/lang_items.rs
+++ b/src/librustc/middle/lang_items.rs
@@ -71,12 +71,12 @@ impl LanguageItems {
         }
     }
 
-    pub fn require(&self, it: LangItem) -> Result<ast::DefId, ~str> {
+    pub fn require(&self, it: LangItem) -> Result<ast::DefId, StrBuf> {
         match self.items.get(it as uint) {
             &Some(id) => Ok(id),
             &None => {
-                Err(format!("requires `{}` lang_item",
-                            LanguageItems::item_name(it as uint)))
+                Err(format_strbuf!("requires `{}` lang_item",
+                                   LanguageItems::item_name(it as uint)))
             }
         }
     }
diff --git a/src/librustc/middle/lint.rs b/src/librustc/middle/lint.rs
index a399fabd95fb6..cc0697ce52769 100644
--- a/src/librustc/middle/lint.rs
+++ b/src/librustc/middle/lint.rs
@@ -1830,7 +1830,7 @@ impl<'a> IdVisitingOperation for Context<'a> {
             None => {}
             Some(l) => {
                 for (lint, span, msg) in l.move_iter() {
-                    self.span_lint(lint, span, msg)
+                    self.span_lint(lint, span, msg.as_slice())
                 }
             }
         }
diff --git a/src/librustc/middle/liveness.rs b/src/librustc/middle/liveness.rs
index 0ca1a07e1a370..f80940a17e238 100644
--- a/src/librustc/middle/liveness.rs
+++ b/src/librustc/middle/liveness.rs
@@ -150,13 +150,19 @@ enum LiveNodeKind {
     ExitNode
 }
 
-fn live_node_kind_to_str(lnk: LiveNodeKind, cx: &ty::ctxt) -> ~str {
+fn live_node_kind_to_str(lnk: LiveNodeKind, cx: &ty::ctxt) -> StrBuf {
     let cm = cx.sess.codemap();
     match lnk {
-        FreeVarNode(s) => format!("Free var node [{}]", cm.span_to_str(s)),
-        ExprNode(s)    => format!("Expr node [{}]", cm.span_to_str(s)),
-        VarDefNode(s)  => format!("Var def node [{}]", cm.span_to_str(s)),
-        ExitNode       => "Exit node".to_owned()
+        FreeVarNode(s) => {
+            format_strbuf!("Free var node [{}]", cm.span_to_str(s))
+        }
+        ExprNode(s) => {
+            format_strbuf!("Expr node [{}]", cm.span_to_str(s))
+        }
+        VarDefNode(s) => {
+            format_strbuf!("Var def node [{}]", cm.span_to_str(s))
+        }
+        ExitNode => "Exit node".to_strbuf(),
     }
 }
 
@@ -308,18 +314,20 @@ impl<'a> IrMaps<'a> {
         match self.variable_map.find(&node_id) {
           Some(&var) => var,
           None => {
-            self.tcx.sess.span_bug(
-                span, format!("no variable registered for id {}", node_id));
+            self.tcx
+                .sess
+                .span_bug(span, format!("no variable registered for id {}",
+                                        node_id));
           }
         }
     }
 
-    fn variable_name(&self, var: Variable) -> ~str {
+    fn variable_name(&self, var: Variable) -> StrBuf {
         match self.var_kinds.get(var.get()) {
             &Local(LocalInfo { ident: nm, .. }) | &Arg(_, nm) => {
-                token::get_ident(nm).get().to_str()
+                token::get_ident(nm).get().to_str().to_strbuf()
             },
-            &ImplicitRet => "<implicit-ret>".to_owned()
+            &ImplicitRet => "<implicit-ret>".to_strbuf()
         }
     }
 
@@ -741,7 +749,7 @@ impl<'a> Liveness<'a> {
     }
 
     #[allow(unused_must_use)]
-    fn ln_str(&self, ln: LiveNode) -> ~str {
+    fn ln_str(&self, ln: LiveNode) -> StrBuf {
         let mut wr = io::MemWriter::new();
         {
             let wr = &mut wr as &mut io::Writer;
@@ -751,7 +759,7 @@ impl<'a> Liveness<'a> {
             self.write_vars(wr, ln, |idx| self.users.get(idx).writer);
             write!(wr, "  precedes {}]", self.successors.get(ln.get()).to_str());
         }
-        str::from_utf8(wr.unwrap().as_slice()).unwrap().to_owned()
+        str::from_utf8(wr.unwrap().as_slice()).unwrap().to_strbuf()
     }
 
     fn init_empty(&mut self, ln: LiveNode, succ_ln: LiveNode) {
@@ -1532,9 +1540,13 @@ impl<'a> Liveness<'a> {
        }
     }
 
-    fn should_warn(&self, var: Variable) -> Option<~str> {
+    fn should_warn(&self, var: Variable) -> Option<StrBuf> {
         let name = self.ir.variable_name(var);
-        if name.len() == 0 || name[0] == ('_' as u8) { None } else { Some(name) }
+        if name.len() == 0 || name.as_slice()[0] == ('_' as u8) {
+            None
+        } else {
+            Some(name)
+        }
     }
 
     fn warn_about_unused_args(&self, decl: &FnDecl, entry_ln: LiveNode) {
@@ -1581,11 +1593,12 @@ impl<'a> Liveness<'a> {
 
                 if is_assigned {
                     self.ir.tcx.sess.add_lint(UnusedVariable, id, sp,
-                        format!("variable `{}` is assigned to, \
-                                  but never used", *name));
+                        format_strbuf!("variable `{}` is assigned to, \
+                                        but never used",
+                                       *name));
                 } else {
                     self.ir.tcx.sess.add_lint(UnusedVariable, id, sp,
-                        format!("unused variable: `{}`", *name));
+                        format_strbuf!("unused variable: `{}`", *name));
                 }
             }
             true
@@ -1603,7 +1616,8 @@ impl<'a> Liveness<'a> {
             let r = self.should_warn(var);
             for name in r.iter() {
                 self.ir.tcx.sess.add_lint(DeadAssignment, id, sp,
-                    format!("value assigned to `{}` is never read", *name));
+                    format_strbuf!("value assigned to `{}` is never read",
+                                   *name));
             }
         }
     }
diff --git a/src/librustc/middle/mem_categorization.rs b/src/librustc/middle/mem_categorization.rs
index 8ff4430a65b6f..bd29398e5225d 100644
--- a/src/librustc/middle/mem_categorization.rs
+++ b/src/librustc/middle/mem_categorization.rs
@@ -1093,50 +1093,51 @@ impl<'t,TYPER:Typer> MemCategorizationContext<'t,TYPER> {
         Ok(())
     }
 
-    pub fn cmt_to_str(&self, cmt: &cmt_) -> ~str {
+    pub fn cmt_to_str(&self, cmt: &cmt_) -> StrBuf {
         match cmt.cat {
           cat_static_item => {
-              "static item".to_owned()
+              "static item".to_strbuf()
           }
           cat_copied_upvar(_) => {
-              "captured outer variable in a proc".to_owned()
+              "captured outer variable in a proc".to_strbuf()
           }
           cat_rvalue(..) => {
-              "non-lvalue".to_owned()
+              "non-lvalue".to_strbuf()
           }
           cat_local(_) => {
-              "local variable".to_owned()
+              "local variable".to_strbuf()
           }
           cat_arg(..) => {
-              "argument".to_owned()
+              "argument".to_strbuf()
           }
           cat_deref(ref base, _, pk) => {
               match base.cat {
                   cat_upvar(..) => {
-                      format!("captured outer variable")
+                      "captured outer variable".to_strbuf()
                   }
                   _ => {
-                      format!("dereference of `{}`-pointer", ptr_sigil(pk))
+                      format_strbuf!("dereference of `{}`-pointer",
+                                     ptr_sigil(pk))
                   }
               }
           }
           cat_interior(_, InteriorField(NamedField(_))) => {
-              "field".to_owned()
+              "field".to_strbuf()
           }
           cat_interior(_, InteriorField(PositionalField(_))) => {
-              "anonymous field".to_owned()
+              "anonymous field".to_strbuf()
           }
           cat_interior(_, InteriorElement(VecElement)) => {
-              "vec content".to_owned()
+              "vec content".to_strbuf()
           }
           cat_interior(_, InteriorElement(StrElement)) => {
-              "str content".to_owned()
+              "str content".to_strbuf()
           }
           cat_interior(_, InteriorElement(OtherElement)) => {
-              "indexed content".to_owned()
+              "indexed content".to_strbuf()
           }
           cat_upvar(..) => {
-              "captured outer variable".to_owned()
+              "captured outer variable".to_strbuf()
           }
           cat_discr(ref cmt, _) => {
             self.cmt_to_str(&**cmt)
@@ -1248,17 +1249,17 @@ impl cmt_ {
 }
 
 impl Repr for cmt_ {
-    fn repr(&self, tcx: &ty::ctxt) -> ~str {
-        format!("\\{{} id:{} m:{:?} ty:{}\\}",
-             self.cat.repr(tcx),
-             self.id,
-             self.mutbl,
-             self.ty.repr(tcx))
+    fn repr(&self, tcx: &ty::ctxt) -> StrBuf {
+        format_strbuf!("\\{{} id:{} m:{:?} ty:{}\\}",
+                       self.cat.repr(tcx),
+                       self.id,
+                       self.mutbl,
+                       self.ty.repr(tcx))
     }
 }
 
 impl Repr for categorization {
-    fn repr(&self, tcx: &ty::ctxt) -> ~str {
+    fn repr(&self, tcx: &ty::ctxt) -> StrBuf {
         match *self {
             cat_static_item |
             cat_rvalue(..) |
@@ -1266,21 +1267,19 @@ impl Repr for categorization {
             cat_local(..) |
             cat_upvar(..) |
             cat_arg(..) => {
-                format!("{:?}", *self)
+                format_strbuf!("{:?}", *self)
             }
             cat_deref(ref cmt, derefs, ptr) => {
-                format!("{}-{}{}->",
-                        cmt.cat.repr(tcx),
-                        ptr_sigil(ptr),
-                        derefs)
+                format_strbuf!("{}-{}{}->",
+                               cmt.cat.repr(tcx),
+                               ptr_sigil(ptr),
+                               derefs)
             }
             cat_interior(ref cmt, interior) => {
-                format!("{}.{}",
-                     cmt.cat.repr(tcx),
-                     interior.repr(tcx))
+                format_strbuf!("{}.{}", cmt.cat.repr(tcx), interior.repr(tcx))
             }
             cat_downcast(ref cmt) => {
-                format!("{}->(enum)", cmt.cat.repr(tcx))
+                format_strbuf!("{}->(enum)", cmt.cat.repr(tcx))
             }
             cat_discr(ref cmt, _) => {
                 cmt.cat.repr(tcx)
@@ -1301,13 +1300,13 @@ pub fn ptr_sigil(ptr: PointerKind) -> &'static str {
 }
 
 impl Repr for InteriorKind {
-    fn repr(&self, _tcx: &ty::ctxt) -> ~str {
+    fn repr(&self, _tcx: &ty::ctxt) -> StrBuf {
         match *self {
             InteriorField(NamedField(fld)) => {
-                token::get_name(fld).get().to_str()
+                token::get_name(fld).get().to_str().to_strbuf()
             }
-            InteriorField(PositionalField(i)) => format!("\\#{:?}", i),
-            InteriorElement(_) => "[]".to_owned(),
+            InteriorField(PositionalField(i)) => format_strbuf!("\\#{:?}", i),
+            InteriorElement(_) => "[]".to_strbuf(),
         }
     }
 }
diff --git a/src/librustc/middle/privacy.rs b/src/librustc/middle/privacy.rs
index a08028f374283..5be9226ef7408 100644
--- a/src/librustc/middle/privacy.rs
+++ b/src/librustc/middle/privacy.rs
@@ -45,7 +45,7 @@ pub type PublicItems = NodeSet;
 /// Result of a checking operation - None => no errors were found. Some => an
 /// error and contains the span and message for reporting that error and
 /// optionally the same for a note about the error.
-type CheckResult = Option<(Span, ~str, Option<(Span, ~str)>)>;
+type CheckResult = Option<(Span, StrBuf, Option<(Span, StrBuf)>)>;
 
 ////////////////////////////////////////////////////////////////////////////////
 /// The parent visitor, used to determine what's the parent of what (node-wise)
@@ -356,8 +356,8 @@ enum FieldName {
 
 impl<'a> PrivacyVisitor<'a> {
     // used when debugging
-    fn nodestr(&self, id: ast::NodeId) -> ~str {
-        self.tcx.map.node_to_str(id).to_owned()
+    fn nodestr(&self, id: ast::NodeId) -> StrBuf {
+        self.tcx.map.node_to_str(id).to_strbuf()
     }
 
     // Determines whether the given definition is public from the point of view
@@ -511,9 +511,11 @@ impl<'a> PrivacyVisitor<'a> {
         match result {
             None => true,
             Some((span, msg, note)) => {
-                self.tcx.sess.span_err(span, msg);
+                self.tcx.sess.span_err(span, msg.as_slice());
                 match note {
-                    Some((span, msg)) => self.tcx.sess.span_note(span, msg),
+                    Some((span, msg)) => {
+                        self.tcx.sess.span_note(span, msg.as_slice())
+                    }
                     None => {},
                 }
                 false
@@ -528,7 +530,9 @@ impl<'a> PrivacyVisitor<'a> {
                      source_did: Option<ast::DefId>, msg: &str) -> CheckResult {
         let id = match self.def_privacy(to_check) {
             ExternallyDenied => {
-                return Some((span, format!("{} is private", msg), None))
+                return Some((span,
+                             format_strbuf!("{} is private", msg),
+                             None))
             }
             Allowable => return None,
             DisallowedBy(id) => id,
@@ -539,9 +543,11 @@ impl<'a> PrivacyVisitor<'a> {
         // because the item itself is private or because its parent is private
         // and its parent isn't in our ancestry.
         let (err_span, err_msg) = if id == source_did.unwrap_or(to_check).node {
-            return Some((span, format!("{} is private", msg), None));
+            return Some((span,
+                         format_strbuf!("{} is private", msg),
+                         None));
         } else {
-            (span, format!("{} is inaccessible", msg))
+            (span, format_strbuf!("{} is inaccessible", msg))
         };
         let item = match self.tcx.map.find(id) {
             Some(ast_map::NodeItem(item)) => {
@@ -577,8 +583,9 @@ impl<'a> PrivacyVisitor<'a> {
             ast::ItemEnum(..) => "enum",
             _ => return Some((err_span, err_msg, None))
         };
-        let msg = format!("{} `{}` is private", desc,
-                          token::get_ident(item.ident));
+        let msg = format_strbuf!("{} `{}` is private",
+                                 desc,
+                                 token::get_ident(item.ident));
         Some((err_span, err_msg, Some((span, msg))))
     }
 
@@ -1364,9 +1371,11 @@ impl<'a> Visitor<()> for VisiblePrivateTypesVisitor<'a> {
         match t.node {
             ast::TyPath(ref p, _, path_id) => {
                 if self.path_is_private_type(path_id) {
-                    self.tcx.sess.add_lint(lint::VisiblePrivateTypes,
-                                           path_id, p.span,
-                                           "private type in exported type signature".to_owned());
+                    self.tcx.sess.add_lint(
+                        lint::VisiblePrivateTypes,
+                        path_id, p.span,
+                        "private type in exported type \
+                         signature".to_strbuf());
                 }
             }
             _ => {}
diff --git a/src/librustc/middle/resolve.rs b/src/librustc/middle/resolve.rs
index 1abdca7cb9f7b..bce82002ecb20 100644
--- a/src/librustc/middle/resolve.rs
+++ b/src/librustc/middle/resolve.rs
@@ -57,7 +57,7 @@ pub type TraitMap = NodeMap<Vec<DefId> >;
 pub type ExportMap2 = RefCell<NodeMap<Vec<Export2> >>;
 
 pub struct Export2 {
-    pub name: ~str,        // The name of the target.
+    pub name: StrBuf,        // The name of the target.
     pub def_id: DefId,     // The definition of the target.
 }
 
@@ -2046,7 +2046,7 @@ impl<'a> Resolver<'a> {
         }
     }
 
-    fn idents_to_str(&mut self, idents: &[Ident]) -> ~str {
+    fn idents_to_str(&mut self, idents: &[Ident]) -> StrBuf {
         let mut first = true;
         let mut result = StrBuf::new();
         for ident in idents.iter() {
@@ -2057,10 +2057,10 @@ impl<'a> Resolver<'a> {
             }
             result.push_str(token::get_ident(*ident).get());
         };
-        result.into_owned()
+        result
     }
 
-    fn path_idents_to_str(&mut self, path: &Path) -> ~str {
+    fn path_idents_to_str(&mut self, path: &Path) -> StrBuf {
         let identifiers: Vec<ast::Ident> = path.segments
                                              .iter()
                                              .map(|seg| seg.identifier)
@@ -2070,25 +2070,26 @@ impl<'a> Resolver<'a> {
 
     fn import_directive_subclass_to_str(&mut self,
                                         subclass: ImportDirectiveSubclass)
-                                        -> ~str {
+                                        -> StrBuf {
         match subclass {
             SingleImport(_, source) => {
-                token::get_ident(source).get().to_str()
+                token::get_ident(source).get().to_strbuf()
             }
-            GlobImport => "*".to_owned()
+            GlobImport => "*".to_strbuf()
         }
     }
 
     fn import_path_to_str(&mut self,
                           idents: &[Ident],
                           subclass: ImportDirectiveSubclass)
-                          -> ~str {
+                          -> StrBuf {
         if idents.is_empty() {
             self.import_directive_subclass_to_str(subclass)
         } else {
             (format!("{}::{}",
                      self.idents_to_str(idents),
-                     self.import_directive_subclass_to_str(subclass)))
+                     self.import_directive_subclass_to_str(
+                         subclass))).to_strbuf()
         }
     }
 
@@ -2219,8 +2220,11 @@ impl<'a> Resolver<'a> {
 
         let lp = match lp {
             LastMod(lp) => lp,
-            LastImport{..} => self.session.span_bug(directive.span,
-                                                    "Not expecting Import here, must be LastMod"),
+            LastImport {..} => {
+                self.session
+                    .span_bug(directive.span,
+                              "not expecting Import here, must be LastMod")
+            }
         };
 
         // We need to resolve both namespaces for this to succeed.
@@ -2614,7 +2618,7 @@ impl<'a> Resolver<'a> {
                 Failed => {
                     let segment_name = token::get_ident(name);
                     let module_name = self.module_to_str(&*search_module);
-                    if "???" == module_name {
+                    if "???" == module_name.as_slice() {
                         let span = Span {
                             lo: span.lo,
                             hi: span.lo + Pos::from_uint(segment_name.get().len()),
@@ -2732,14 +2736,18 @@ impl<'a> Resolver<'a> {
         match module_prefix_result {
             Failed => {
                 let mpath = self.idents_to_str(module_path);
-                match mpath.rfind(':') {
+                match mpath.as_slice().rfind(':') {
                     Some(idx) => {
-                        self.resolve_error(span, format!("unresolved import: could not find `{}` \
-                                                         in `{}`",
-                                                         // idx +- 1 to account for the colons
-                                                         // on either side
-                                                         mpath.slice_from(idx + 1),
-                                                         mpath.slice_to(idx - 1)));
+                        self.resolve_error(span,
+                                           format!("unresolved import: could \
+                                                    not find `{}` in `{}`",
+                                                   // idx +- 1 to account for
+                                                   // the colons on either
+                                                   // side
+                                                   mpath.as_slice()
+                                                        .slice_from(idx + 1),
+                                                   mpath.as_slice()
+                                                        .slice_to(idx - 1)));
                     },
                     None => (),
                 };
@@ -3283,7 +3291,7 @@ impl<'a> Resolver<'a> {
                 debug!("(computing exports) YES: export '{}' => {:?}",
                        name, def_id_of_def(d));
                 exports2.push(Export2 {
-                    name: name.get().to_str(),
+                    name: name.get().to_strbuf(),
                     def_id: def_id_of_def(d)
                 });
             }
@@ -4557,10 +4565,11 @@ impl<'a> Resolver<'a> {
             let def = self.resolve_module_relative_path(path, namespace);
             match (def, unqualified_def) {
                 (Some((d, _)), Some((ud, _))) if d == ud => {
-                    self.session.add_lint(UnnecessaryQualification,
-                                          id,
-                                          path.span,
-                                          "unnecessary qualification".to_owned());
+                    self.session
+                        .add_lint(UnnecessaryQualification,
+                                  id,
+                                  path.span,
+                                  "unnecessary qualification".to_strbuf());
                 }
                 _ => ()
             }
@@ -4875,7 +4884,7 @@ impl<'a> Resolver<'a> {
     }
 
     fn find_best_match_for_name(&mut self, name: &str, max_distance: uint)
-                                -> Option<~str> {
+                                -> Option<StrBuf> {
         let this = &mut *self;
 
         let mut maybes: Vec<token::InternedString> = Vec::new();
@@ -4907,7 +4916,7 @@ impl<'a> Resolver<'a> {
             *values.get(smallest) <= max_distance &&
             name != maybes.get(smallest).get() {
 
-            Some(maybes.get(smallest).get().to_str())
+            Some(maybes.get(smallest).get().to_strbuf())
 
         } else {
             None
@@ -4977,17 +4986,20 @@ impl<'a> Resolver<'a> {
                             _ =>
                                // limit search to 5 to reduce the number
                                // of stupid suggestions
-                               match self.find_best_match_for_name(wrong_name, 5) {
+                               match self.find_best_match_for_name(
+                                        wrong_name.as_slice(),
+                                        5) {
                                    Some(m) => {
                                        self.resolve_error(expr.span,
                                            format!("unresolved name `{}`. \
                                                     Did you mean `{}`?",
-                                                    wrong_name, m));
+                                                    wrong_name,
+                                                    m));
                                    }
                                    None => {
                                        self.resolve_error(expr.span,
                                             format!("unresolved name `{}`.",
-                                                    wrong_name));
+                                                    wrong_name.as_slice()));
                                    }
                                }
                         }
@@ -5240,8 +5252,11 @@ impl<'a> Resolver<'a> {
                     ViewPathGlob(_, id) => {
                         if !self.used_imports.contains(&(id, TypeNS)) &&
                            !self.used_imports.contains(&(id, ValueNS)) {
-                            self.session.add_lint(UnusedImports, id, p.span,
-                                                  "unused import".to_owned());
+                            self.session
+                                .add_lint(UnusedImports,
+                                          id,
+                                          p.span,
+                                          "unused import".to_strbuf());
                         }
                     },
                 }
@@ -5257,19 +5272,27 @@ impl<'a> Resolver<'a> {
     // public or private item, we will check the correct thing, dependent on how the import
     // is used.
     fn finalize_import(&mut self, id: NodeId, span: Span) {
-        debug!("finalizing import uses for {}", self.session.codemap().span_to_snippet(span));
+        debug!("finalizing import uses for {}",
+               self.session.codemap().span_to_snippet(span));
 
         if !self.used_imports.contains(&(id, TypeNS)) &&
            !self.used_imports.contains(&(id, ValueNS)) {
-            self.session.add_lint(UnusedImports, id, span, "unused import".to_owned());
+            self.session.add_lint(UnusedImports,
+                                  id,
+                                  span,
+                                  "unused import".to_strbuf());
         }
 
         let (v_priv, t_priv) = match self.last_private.find(&id) {
-            Some(&LastImport{value_priv: v,
-                             value_used: _,
-                             type_priv: t,
-                             type_used: _}) => (v, t),
-            Some(_) => fail!("We should only have LastImport for `use` directives"),
+            Some(&LastImport {
+                value_priv: v,
+                value_used: _,
+                type_priv: t,
+                type_used: _
+            }) => (v, t),
+            Some(_) => {
+                fail!("we should only have LastImport for `use` directives")
+            }
             _ => return,
         };
 
@@ -5306,7 +5329,7 @@ impl<'a> Resolver<'a> {
     //
 
     /// A somewhat inefficient routine to obtain the name of a module.
-    fn module_to_str(&mut self, module: &Module) -> ~str {
+    fn module_to_str(&mut self, module: &Module) -> StrBuf {
         let mut idents = Vec::new();
 
         fn collect_mod(idents: &mut Vec<ast::Ident>, module: &Module) {
@@ -5325,7 +5348,7 @@ impl<'a> Resolver<'a> {
         collect_mod(&mut idents, module);
 
         if idents.len() == 0 {
-            return "???".to_owned();
+            return "???".to_strbuf();
         }
         self.idents_to_str(idents.move_iter().rev()
                                  .collect::<Vec<ast::Ident>>()
diff --git a/src/librustc/middle/trans/_match.rs b/src/librustc/middle/trans/_match.rs
index abb9be62dd8d4..e609da6c33ddc 100644
--- a/src/librustc/middle/trans/_match.rs
+++ b/src/librustc/middle/trans/_match.rs
@@ -400,12 +400,12 @@ struct Match<'a, 'b> {
 }
 
 impl<'a, 'b> Repr for Match<'a, 'b> {
-    fn repr(&self, tcx: &ty::ctxt) -> ~str {
+    fn repr(&self, tcx: &ty::ctxt) -> StrBuf {
         if tcx.sess.verbose() {
             // for many programs, this just take too long to serialize
             self.pats.repr(tcx)
         } else {
-            format!("{} pats", self.pats.len())
+            format_strbuf!("{} pats", self.pats.len())
         }
     }
 }
@@ -1851,11 +1851,14 @@ fn create_bindings_map(bcx: &Block, pat: @ast::Pat) -> BindingsMap {
                 // but during matching we need to store a *T as explained
                 // above
                 llmatch = alloca(bcx, llvariable_ty.ptr_to(), "__llmatch");
-                trmode = TrByValue(alloca(bcx, llvariable_ty,
-                                          bcx.ident(ident)));
+                trmode = TrByValue(alloca(bcx,
+                                          llvariable_ty,
+                                          bcx.ident(ident).as_slice()));
             }
             ast::BindByRef(_) => {
-                llmatch = alloca(bcx, llvariable_ty, bcx.ident(ident));
+                llmatch = alloca(bcx,
+                                 llvariable_ty,
+                                 bcx.ident(ident).as_slice());
                 trmode = TrByRef;
             }
         };
@@ -2103,7 +2106,7 @@ fn mk_binding_alloca<'a,A>(bcx: &'a Block<'a>,
     let ident = ast_util::path_to_ident(path);
 
     // Allocate memory on stack for the binding.
-    let llval = alloc_ty(bcx, var_ty, bcx.ident(ident));
+    let llval = alloc_ty(bcx, var_ty, bcx.ident(ident).as_slice());
 
     // Subtle: be sure that we *populate* the memory *before*
     // we schedule the cleanup.
diff --git a/src/librustc/middle/trans/asm.rs b/src/librustc/middle/trans/asm.rs
index d6636854713a8..e6004b4cb71f7 100644
--- a/src/librustc/middle/trans/asm.rs
+++ b/src/librustc/middle/trans/asm.rs
@@ -65,15 +65,13 @@ pub fn trans_inline_asm<'a>(bcx: &'a Block<'a>, ia: &ast::InlineAsm)
 
     let mut constraints =
         StrBuf::from_str(constraints.iter()
-                                    .map(|s| s.get().to_str())
-                                    .collect::<Vec<~str>>()
+                                    .map(|s| s.get().to_strbuf())
+                                    .collect::<Vec<StrBuf>>()
                                     .connect(","));
 
-    let mut clobbers = StrBuf::from_str(getClobbers());
+    let mut clobbers = getClobbers();
     if !ia.clobbers.get().is_empty() && !clobbers.is_empty() {
-        clobbers = StrBuf::from_owned_str(format!("{},{}",
-                                                  ia.clobbers.get(),
-                                                  clobbers));
+        clobbers = format_strbuf!("{},{}", ia.clobbers.get(), clobbers);
     } else {
         clobbers.push_str(ia.clobbers.get());
     }
@@ -136,12 +134,12 @@ pub fn trans_inline_asm<'a>(bcx: &'a Block<'a>, ia: &ast::InlineAsm)
 
 #[cfg(target_arch = "arm")]
 #[cfg(target_arch = "mips")]
-fn getClobbers() -> ~str {
-    "".to_owned()
+fn getClobbers() -> StrBuf {
+    "".to_strbuf()
 }
 
 #[cfg(target_arch = "x86")]
 #[cfg(target_arch = "x86_64")]
-fn getClobbers() -> ~str {
-    "~{dirflag},~{fpsr},~{flags}".to_owned()
+fn getClobbers() -> StrBuf {
+    "~{dirflag},~{fpsr},~{flags}".to_strbuf()
 }
diff --git a/src/librustc/middle/trans/base.rs b/src/librustc/middle/trans/base.rs
index 2d3497b52296b..10f35255abb86 100644
--- a/src/librustc/middle/trans/base.rs
+++ b/src/librustc/middle/trans/base.rs
@@ -124,13 +124,13 @@ pub fn push_ctxt(s: &'static str) -> _InsnCtxt {
 
 pub struct StatRecorder<'a> {
     ccx: &'a CrateContext,
-    name: Option<~str>,
+    name: Option<StrBuf>,
     start: u64,
     istart: uint,
 }
 
 impl<'a> StatRecorder<'a> {
-    pub fn new(ccx: &'a CrateContext, name: ~str) -> StatRecorder<'a> {
+    pub fn new(ccx: &'a CrateContext, name: StrBuf) -> StatRecorder<'a> {
         let start = if ccx.sess().trans_stats() {
             time::precise_time_ns()
         } else {
@@ -206,15 +206,19 @@ pub fn decl_cdecl_fn(llmod: ModuleRef,
 }
 
 // only use this for foreign function ABIs and glue, use `get_extern_rust_fn` for Rust functions
-pub fn get_extern_fn(externs: &mut ExternMap, llmod: ModuleRef,
-                     name: &str, cc: lib::llvm::CallConv,
-                     ty: Type, output: ty::t) -> ValueRef {
+pub fn get_extern_fn(externs: &mut ExternMap,
+                     llmod: ModuleRef,
+                     name: &str,
+                     cc: lib::llvm::CallConv,
+                     ty: Type,
+                     output: ty::t)
+                     -> ValueRef {
     match externs.find_equiv(&name) {
         Some(n) => return *n,
         None => {}
     }
     let f = decl_fn(llmod, name, cc, ty, output);
-    externs.insert(name.to_owned(), f);
+    externs.insert(name.to_strbuf(), f);
     f
 }
 
@@ -231,7 +235,7 @@ fn get_extern_rust_fn(ccx: &CrateContext, inputs: &[ty::t], output: ty::t,
                                     .collect::<Vec<_>>().as_slice(), f)
     });
 
-    ccx.externs.borrow_mut().insert(name.to_owned(), f);
+    ccx.externs.borrow_mut().insert(name.to_strbuf(), f);
     f
 }
 
@@ -315,7 +319,7 @@ pub fn get_extern_const(externs: &mut ExternMap, llmod: ModuleRef,
         let c = name.with_c_str(|buf| {
             llvm::LLVMAddGlobal(llmod, ty.to_ref(), buf)
         });
-        externs.insert(name.to_owned(), c);
+        externs.insert(name.to_strbuf(), c);
         return c;
     }
 }
@@ -469,9 +473,9 @@ pub fn unset_split_stack(f: ValueRef) {
 
 // Double-check that we never ask LLVM to declare the same symbol twice. It
 // silently mangles such symbols, breaking our linkage model.
-pub fn note_unique_llvm_symbol(ccx: &CrateContext, sym: ~str) {
+pub fn note_unique_llvm_symbol(ccx: &CrateContext, sym: StrBuf) {
     if ccx.all_llvm_symbols.borrow().contains(&sym) {
-        ccx.sess().bug("duplicate LLVM symbol: ".to_owned() + sym);
+        ccx.sess().bug(format!("duplicate LLVM symbol: {}", sym));
     }
     ccx.all_llvm_symbols.borrow_mut().insert(sym);
 }
@@ -505,8 +509,12 @@ pub fn get_res_dtor(ccx: &CrateContext,
                                  ty::lookup_item_type(tcx, parent_id).ty);
         let llty = type_of_dtor(ccx, class_ty);
 
-        get_extern_fn(&mut *ccx.externs.borrow_mut(), ccx.llmod, name,
-                      lib::llvm::CCallConv, llty, ty::mk_nil())
+        get_extern_fn(&mut *ccx.externs.borrow_mut(),
+                      ccx.llmod,
+                      name.as_slice(),
+                      lib::llvm::CCallConv,
+                      llty,
+                      ty::mk_nil())
     }
 }
 
@@ -829,8 +837,8 @@ pub fn fail_if_zero<'a>(
         ICmp(cx, lib::llvm::IntEQ, rhs, zero)
       }
       _ => {
-        cx.sess().bug("fail-if-zero on unexpected type: ".to_owned() +
-                      ty_to_str(cx.tcx(), rhs_t));
+        cx.sess().bug(format!("fail-if-zero on unexpected type: {}",
+                              ty_to_str(cx.tcx(), rhs_t)));
       }
     };
     with_cond(cx, is_zero, |bcx| {
@@ -848,15 +856,19 @@ pub fn trans_external_path(ccx: &CrateContext, did: ast::DefId, t: ty::t) -> Val
                     get_extern_rust_fn(ccx,
                                        fn_ty.sig.inputs.as_slice(),
                                        fn_ty.sig.output,
-                                       name,
+                                       name.as_slice(),
                                        did)
                 }
                 Some(..) | None => {
                     let c = foreign::llvm_calling_convention(ccx, fn_ty.abi);
                     let cconv = c.unwrap_or(lib::llvm::CCallConv);
                     let llty = type_of_fn_from_ty(ccx, t);
-                    get_extern_fn(&mut *ccx.externs.borrow_mut(), ccx.llmod,
-                                  name, cconv, llty, fn_ty.sig.output)
+                    get_extern_fn(&mut *ccx.externs.borrow_mut(),
+                                  ccx.llmod,
+                                  name.as_slice(),
+                                  cconv,
+                                  llty,
+                                  fn_ty.sig.output)
                 }
             }
         }
@@ -864,12 +876,14 @@ pub fn trans_external_path(ccx: &CrateContext, did: ast::DefId, t: ty::t) -> Val
             get_extern_rust_fn(ccx,
                                f.sig.inputs.as_slice(),
                                f.sig.output,
-                               name,
+                               name.as_slice(),
                                did)
         }
         _ => {
             let llty = type_of(ccx, t);
-            get_extern_const(&mut *ccx.externs.borrow_mut(), ccx.llmod, name,
+            get_extern_const(&mut *ccx.externs.borrow_mut(),
+                             ccx.llmod,
+                             name.as_slice(),
                              llty)
         }
     }
@@ -1443,7 +1457,7 @@ pub fn trans_fn(ccx: &CrateContext,
                 param_substs: Option<&param_substs>,
                 id: ast::NodeId,
                 attrs: &[ast::Attribute]) {
-    let _s = StatRecorder::new(ccx, ccx.tcx.map.path_to_str(id).to_owned());
+    let _s = StatRecorder::new(ccx, ccx.tcx.map.path_to_str(id).to_strbuf());
     debug!("trans_fn(param_substs={})", param_substs.map(|s| s.repr(ccx.tcx())));
     let _icx = push_ctxt("trans_fn");
     let output_type = ty::ty_fn_ret(ty::node_id_to_type(ccx.tcx(), id));
@@ -1661,7 +1675,7 @@ pub fn trans_mod(ccx: &CrateContext, m: &ast::Mod) {
     }
 }
 
-fn finish_register_fn(ccx: &CrateContext, sp: Span, sym: ~str, node_id: ast::NodeId,
+fn finish_register_fn(ccx: &CrateContext, sp: Span, sym: StrBuf, node_id: ast::NodeId,
                       llfn: ValueRef) {
     ccx.item_symbols.borrow_mut().insert(node_id, sym);
 
@@ -1676,7 +1690,7 @@ fn finish_register_fn(ccx: &CrateContext, sp: Span, sym: ~str, node_id: ast::Nod
 
 fn register_fn(ccx: &CrateContext,
                sp: Span,
-               sym: ~str,
+               sym: StrBuf,
                node_id: ast::NodeId,
                node_type: ty::t)
                -> ValueRef {
@@ -1692,7 +1706,7 @@ fn register_fn(ccx: &CrateContext,
                             false,
                             f.sig.inputs.as_slice(),
                             f.sig.output,
-                            sym);
+                            sym.as_slice());
     finish_register_fn(ccx, sp, sym, node_id, llfn);
     llfn
 }
@@ -1700,14 +1714,14 @@ fn register_fn(ccx: &CrateContext,
 // only use this for foreign function ABIs and glue, use `register_fn` for Rust functions
 pub fn register_fn_llvmty(ccx: &CrateContext,
                           sp: Span,
-                          sym: ~str,
+                          sym: StrBuf,
                           node_id: ast::NodeId,
                           cc: lib::llvm::CallConv,
                           fn_ty: Type,
                           output: ty::t) -> ValueRef {
     debug!("register_fn_llvmty id={} sym={}", node_id, sym);
 
-    let llfn = decl_fn(ccx.llmod, sym, cc, fn_ty, output);
+    let llfn = decl_fn(ccx.llmod, sym.as_slice(), cc, fn_ty, output);
     finish_register_fn(ccx, sp, sym, node_id, llfn);
     llfn
 }
@@ -1752,7 +1766,7 @@ pub fn create_entry_wrapper(ccx: &CrateContext,
             let (start_fn, args) = if use_start_lang_item {
                 let start_def_id = match ccx.tcx.lang_items.require(StartFnLangItem) {
                     Ok(id) => id,
-                    Err(s) => { ccx.sess().fatal(s); }
+                    Err(s) => { ccx.sess().fatal(s.as_slice()); }
                 };
                 let start_fn = if start_def_id.krate == ast::LOCAL_CRATE {
                     get_item_val(ccx, start_def_id.node)
@@ -1796,15 +1810,15 @@ pub fn create_entry_wrapper(ccx: &CrateContext,
 }
 
 fn exported_name(ccx: &CrateContext, id: ast::NodeId,
-                 ty: ty::t, attrs: &[ast::Attribute]) -> ~str {
+                 ty: ty::t, attrs: &[ast::Attribute]) -> StrBuf {
     match attr::first_attr_value_str_by_name(attrs, "export_name") {
         // Use provided name
-        Some(name) => name.get().to_owned(),
+        Some(name) => name.get().to_strbuf(),
 
         _ => ccx.tcx.map.with_path(id, |mut path| {
             if attr::contains_name(attrs, "no_mangle") {
                 // Don't mangle
-                path.last().unwrap().to_str()
+                path.last().unwrap().to_str().to_strbuf()
             } else {
                 // Usual name mangling
                 mangle_exported_name(ccx, path, ty, id)
@@ -1854,7 +1868,7 @@ pub fn get_item_val(ccx: &CrateContext, id: ast::NodeId) -> ValueRef {
 
                     unsafe {
                         let llty = llvm::LLVMTypeOf(v);
-                        let g = sym.with_c_str(|buf| {
+                        let g = sym.as_slice().with_c_str(|buf| {
                             llvm::LLVMAddGlobal(ccx.llmod, llty, buf)
                         });
 
@@ -2096,7 +2110,12 @@ pub fn write_metadata(cx: &CrateContext, krate: &ast::Crate) -> Vec<u8> {
     });
     unsafe {
         llvm::LLVMSetInitializer(llglobal, llconst);
-        cx.sess().targ_cfg.target_strs.meta_sect_name.with_c_str(|buf| {
+        cx.sess()
+          .targ_cfg
+          .target_strs
+          .meta_sect_name
+          .as_slice()
+          .with_c_str(|buf| {
             llvm::LLVMSetSection(llglobal, buf)
         });
     }
@@ -2126,7 +2145,8 @@ pub fn trans_crate(krate: ast::Crate,
         }
     }
 
-    let link_meta = link::build_link_meta(&krate, output.out_filestem);
+    let link_meta = link::build_link_meta(&krate,
+                                          output.out_filestem.as_slice());
 
     // Append ".rs" to crate name as LLVM module identifier.
     //
@@ -2186,8 +2206,8 @@ pub fn trans_crate(krate: ast::Crate,
     let link_meta = ccx.link_meta.clone();
     let llmod = ccx.llmod;
 
-    let mut reachable: Vec<~str> = ccx.reachable.iter().filter_map(|id| {
-        ccx.item_symbols.borrow().find(id).map(|s| s.to_owned())
+    let mut reachable: Vec<StrBuf> = ccx.reachable.iter().filter_map(|id| {
+        ccx.item_symbols.borrow().find(id).map(|s| s.to_strbuf())
     }).collect();
 
     // Make sure that some other crucial symbols are not eliminated from the
@@ -2196,12 +2216,13 @@ pub fn trans_crate(krate: ast::Crate,
     // symbol. This symbol is required for use by the libmorestack library that
     // we link in, so we must ensure that this symbol is not internalized (if
     // defined in the crate).
-    reachable.push("main".to_owned());
-    reachable.push("rust_stack_exhausted".to_owned());
+    reachable.push("main".to_strbuf());
+    reachable.push("rust_stack_exhausted".to_strbuf());
 
     // referenced from .eh_frame section on some platforms
-    reachable.push("rust_eh_personality".to_owned());
-    reachable.push("rust_eh_personality_catch".to_owned()); // referenced from rt/rust_try.ll
+    reachable.push("rust_eh_personality".to_strbuf());
+    // referenced from rt/rust_try.ll
+    reachable.push("rust_eh_personality_catch".to_strbuf());
 
     let metadata_module = ccx.metadata_llmod;
     let formats = ccx.tcx.dependency_formats.borrow().clone();
diff --git a/src/librustc/middle/trans/build.rs b/src/librustc/middle/trans/build.rs
index 65db4bdc9ab9d..bc4a2d9f96fb0 100644
--- a/src/librustc/middle/trans/build.rs
+++ b/src/librustc/middle/trans/build.rs
@@ -122,7 +122,7 @@ pub fn Invoke(cx: &Block,
     terminate(cx, "Invoke");
     debug!("Invoke({} with arguments ({}))",
            cx.val_to_str(fn_),
-           args.iter().map(|a| cx.val_to_str(*a)).collect::<Vec<~str>>().connect(", "));
+           args.iter().map(|a| cx.val_to_str(*a)).collect::<Vec<StrBuf>>().connect(", "));
     B(cx).invoke(fn_, args, then, catch, attributes)
 }
 
diff --git a/src/librustc/middle/trans/builder.rs b/src/librustc/middle/trans/builder.rs
index a02453a2554f4..17667003506b1 100644
--- a/src/librustc/middle/trans/builder.rs
+++ b/src/librustc/middle/trans/builder.rs
@@ -81,8 +81,7 @@ impl<'a> Builder<'a> {
                 s.push_char('/');
                 s.push_str(category);
 
-                let s = s.into_owned();
-                let n = match h.find_equiv(&s) {
+                let n = match h.find(&s) {
                     Some(&n) => n,
                     _ => 0u
                 };
@@ -805,7 +804,7 @@ impl<'a> Builder<'a> {
                self.ccx.tn.val_to_str(llfn),
                args.iter()
                    .map(|&v| self.ccx.tn.val_to_str(v))
-                   .collect::<Vec<~str>>()
+                   .collect::<Vec<StrBuf>>()
                    .connect(", "));
 
         unsafe {
diff --git a/src/librustc/middle/trans/cleanup.rs b/src/librustc/middle/trans/cleanup.rs
index b9b44b72b10da..776de01614d6b 100644
--- a/src/librustc/middle/trans/cleanup.rs
+++ b/src/librustc/middle/trans/cleanup.rs
@@ -599,7 +599,9 @@ impl<'a> CleanupHelperMethods<'a> for FunctionContext<'a> {
             {
                 let name = scope.block_name("clean");
                 debug!("generating cleanups for {}", name);
-                let bcx_in = self.new_block(label.is_unwind(), name, None);
+                let bcx_in = self.new_block(label.is_unwind(),
+                                            name.as_slice(),
+                                            None);
                 let mut bcx_out = bcx_in;
                 for cleanup in scope.cleanups.iter().rev() {
                     if cleanup_is_suitable_for(*cleanup, label) {
@@ -649,7 +651,7 @@ impl<'a> CleanupHelperMethods<'a> for FunctionContext<'a> {
                 Some(llbb) => { return llbb; }
                 None => {
                     let name = last_scope.block_name("unwind");
-                    pad_bcx = self.new_block(true, name, None);
+                    pad_bcx = self.new_block(true, name.as_slice(), None);
                     last_scope.cached_landing_pad = Some(pad_bcx.llbb);
                 }
             }
@@ -731,16 +733,16 @@ impl<'a> CleanupScope<'a> {
             self.cleanups.iter().any(|c| c.clean_on_unwind())
     }
 
-    fn block_name(&self, prefix: &str) -> ~str {
+    fn block_name(&self, prefix: &str) -> StrBuf {
         /*!
          * Returns a suitable name to use for the basic block that
          * handles this cleanup scope
          */
 
         match self.kind {
-            CustomScopeKind => format!("{}_custom_", prefix),
-            AstScopeKind(id) => format!("{}_ast_{}_", prefix, id),
-            LoopScopeKind(id, _) => format!("{}_loop_{}_", prefix, id),
+            CustomScopeKind => format_strbuf!("{}_custom_", prefix),
+            AstScopeKind(id) => format_strbuf!("{}_ast_{}_", prefix, id),
+            LoopScopeKind(id, _) => format_strbuf!("{}_loop_{}_", prefix, id),
         }
     }
 }
diff --git a/src/librustc/middle/trans/closure.rs b/src/librustc/middle/trans/closure.rs
index 1f4ea02bcc648..80d35d88b2137 100644
--- a/src/librustc/middle/trans/closure.rs
+++ b/src/librustc/middle/trans/closure.rs
@@ -104,8 +104,8 @@ pub struct EnvValue {
 }
 
 impl EnvValue {
-    pub fn to_str(&self, ccx: &CrateContext) -> ~str {
-        format!("{}({})", self.action, self.datum.to_str(ccx))
+    pub fn to_str(&self, ccx: &CrateContext) -> StrBuf {
+        format_strbuf!("{}({})", self.action, self.datum.to_str(ccx))
     }
 }
 
@@ -354,7 +354,7 @@ pub fn trans_expr_fn<'a>(
                                      true,
                                      f.sig.inputs.as_slice(),
                                      f.sig.output,
-                                     s);
+                                     s.as_slice());
 
     // set an inline hint for all closures
     set_inline_hint(llfn);
@@ -417,9 +417,13 @@ pub fn get_wrapper_for_bare_fn(ccx: &CrateContext,
                               true,
                               f.sig.inputs.as_slice(),
                               f.sig.output,
-                              name)
+                              name.as_slice())
     } else {
-        decl_rust_fn(ccx, true, f.sig.inputs.as_slice(), f.sig.output, name)
+        decl_rust_fn(ccx,
+                     true,
+                     f.sig.inputs.as_slice(),
+                     f.sig.output,
+                     name.as_slice())
     };
 
     ccx.closure_bare_wrapper_cache.borrow_mut().insert(fn_ptr, llfn);
diff --git a/src/librustc/middle/trans/common.rs b/src/librustc/middle/trans/common.rs
index e438477a4a3f8..75015bd2d9d2b 100644
--- a/src/librustc/middle/trans/common.rs
+++ b/src/librustc/middle/trans/common.rs
@@ -173,7 +173,7 @@ pub fn BuilderRef_res(b: BuilderRef) -> BuilderRef_res {
     }
 }
 
-pub type ExternMap = HashMap<~str, ValueRef>;
+pub type ExternMap = HashMap<StrBuf, ValueRef>;
 
 // Here `self_ty` is the real type of the self parameter to this method. It
 // will only be set in the case of default methods.
@@ -194,12 +194,12 @@ impl param_substs {
     }
 }
 
-fn param_substs_to_str(this: &param_substs, tcx: &ty::ctxt) -> ~str {
-    format!("param_substs({})", this.substs.repr(tcx))
+fn param_substs_to_str(this: &param_substs, tcx: &ty::ctxt) -> StrBuf {
+    format_strbuf!("param_substs({})", this.substs.repr(tcx))
 }
 
 impl Repr for param_substs {
-    fn repr(&self, tcx: &ty::ctxt) -> ~str {
+    fn repr(&self, tcx: &ty::ctxt) -> StrBuf {
         param_substs_to_str(self, tcx)
     }
 }
@@ -442,15 +442,15 @@ impl<'a> Block<'a> {
     }
     pub fn sess(&self) -> &'a Session { self.fcx.ccx.sess() }
 
-    pub fn ident(&self, ident: Ident) -> ~str {
-        token::get_ident(ident).get().to_str()
+    pub fn ident(&self, ident: Ident) -> StrBuf {
+        token::get_ident(ident).get().to_strbuf()
     }
 
-    pub fn node_id_to_str(&self, id: ast::NodeId) -> ~str {
-        self.tcx().map.node_to_str(id).to_owned()
+    pub fn node_id_to_str(&self, id: ast::NodeId) -> StrBuf {
+        self.tcx().map.node_to_str(id).to_strbuf()
     }
 
-    pub fn expr_to_str(&self, e: &ast::Expr) -> ~str {
+    pub fn expr_to_str(&self, e: &ast::Expr) -> StrBuf {
         e.repr(self.tcx())
     }
 
@@ -464,21 +464,21 @@ impl<'a> Block<'a> {
         }
     }
 
-    pub fn val_to_str(&self, val: ValueRef) -> ~str {
+    pub fn val_to_str(&self, val: ValueRef) -> StrBuf {
         self.ccx().tn.val_to_str(val)
     }
 
-    pub fn llty_str(&self, ty: Type) -> ~str {
+    pub fn llty_str(&self, ty: Type) -> StrBuf {
         self.ccx().tn.type_to_str(ty)
     }
 
-    pub fn ty_to_str(&self, t: ty::t) -> ~str {
+    pub fn ty_to_str(&self, t: ty::t) -> StrBuf {
         t.repr(self.tcx())
     }
 
-    pub fn to_str(&self) -> ~str {
+    pub fn to_str(&self) -> StrBuf {
         let blk: *Block = self;
-        format!("[block {}]", blk)
+        format_strbuf!("[block {}]", blk)
     }
 }
 
diff --git a/src/librustc/middle/trans/context.rs b/src/librustc/middle/trans/context.rs
index 777c03fa6068b..71fcb0b4de559 100644
--- a/src/librustc/middle/trans/context.rs
+++ b/src/librustc/middle/trans/context.rs
@@ -45,9 +45,9 @@ pub struct Stats {
     pub n_inlines: Cell<uint>,
     pub n_closures: Cell<uint>,
     pub n_llvm_insns: Cell<uint>,
-    pub llvm_insns: RefCell<HashMap<~str, uint>>,
+    pub llvm_insns: RefCell<HashMap<StrBuf, uint>>,
     // (ident, time-in-ms, llvm-instructions)
-    pub fn_stats: RefCell<Vec<(~str, uint, uint)> >,
+    pub fn_stats: RefCell<Vec<(StrBuf, uint, uint)> >,
 }
 
 pub struct CrateContext {
@@ -60,7 +60,7 @@ pub struct CrateContext {
     pub item_vals: RefCell<NodeMap<ValueRef>>,
     pub exp_map2: resolve::ExportMap2,
     pub reachable: NodeSet,
-    pub item_symbols: RefCell<NodeMap<~str>>,
+    pub item_symbols: RefCell<NodeMap<StrBuf>>,
     pub link_meta: LinkMeta,
     pub drop_glues: RefCell<HashMap<ty::t, ValueRef>>,
     pub tydescs: RefCell<HashMap<ty::t, Rc<tydesc_info>>>,
@@ -109,8 +109,8 @@ pub struct CrateContext {
     pub llsizingtypes: RefCell<HashMap<ty::t, Type>>,
     pub adt_reprs: RefCell<HashMap<ty::t, Rc<adt::Repr>>>,
     pub symbol_hasher: RefCell<Sha256>,
-    pub type_hashcodes: RefCell<HashMap<ty::t, ~str>>,
-    pub all_llvm_symbols: RefCell<HashSet<~str>>,
+    pub type_hashcodes: RefCell<HashMap<ty::t, StrBuf>>,
+    pub all_llvm_symbols: RefCell<HashSet<StrBuf>>,
     pub tcx: ty::ctxt,
     pub stats: Stats,
     pub int_type: Type,
@@ -141,16 +141,30 @@ impl CrateContext {
             let metadata_llmod = format!("{}_metadata", name).with_c_str(|buf| {
                 llvm::LLVMModuleCreateWithNameInContext(buf, llcx)
             });
-            tcx.sess.targ_cfg.target_strs.data_layout.with_c_str(|buf| {
+            tcx.sess
+               .targ_cfg
+               .target_strs
+               .data_layout
+               .as_slice()
+               .with_c_str(|buf| {
                 llvm::LLVMSetDataLayout(llmod, buf);
                 llvm::LLVMSetDataLayout(metadata_llmod, buf);
             });
-            tcx.sess.targ_cfg.target_strs.target_triple.with_c_str(|buf| {
+            tcx.sess
+               .targ_cfg
+               .target_strs
+               .target_triple
+               .as_slice()
+               .with_c_str(|buf| {
                 llvm::LLVMRustSetNormalizedTarget(llmod, buf);
                 llvm::LLVMRustSetNormalizedTarget(metadata_llmod, buf);
             });
 
-            let td = mk_target_data(tcx.sess.targ_cfg.target_strs.data_layout);
+            let td = mk_target_data(tcx.sess
+                                       .targ_cfg
+                                       .target_strs
+                                       .data_layout
+                                       .as_slice());
 
             let dbg_cx = if tcx.sess.opts.debuginfo != NoDebugInfo {
                 Some(debuginfo::CrateDebugContext::new(llmod))
diff --git a/src/librustc/middle/trans/controlflow.rs b/src/librustc/middle/trans/controlflow.rs
index ec43e6e286f7d..3b3852b3f45b1 100644
--- a/src/librustc/middle/trans/controlflow.rs
+++ b/src/librustc/middle/trans/controlflow.rs
@@ -40,7 +40,7 @@ pub fn trans_stmt<'a>(cx: &'a Block<'a>,
     debug!("trans_stmt({})", s.repr(cx.tcx()));
 
     if cx.sess().asm_comments() {
-        add_span_comment(cx, s.span, s.repr(cx.tcx()));
+        add_span_comment(cx, s.span, s.repr(cx.tcx()).as_slice());
     }
 
     let mut bcx = cx;
diff --git a/src/librustc/middle/trans/datum.rs b/src/librustc/middle/trans/datum.rs
index 6af483bce9519..6907237980202 100644
--- a/src/librustc/middle/trans/datum.rs
+++ b/src/librustc/middle/trans/datum.rs
@@ -624,11 +624,11 @@ impl<K:KindOps> Datum<K> {
     }
 
     #[allow(dead_code)] // useful for debugging
-    pub fn to_str(&self, ccx: &CrateContext) -> ~str {
-        format!("Datum({}, {}, {:?})",
-             ccx.tn.val_to_str(self.val),
-             ty_to_str(ccx.tcx(), self.ty),
-             self.kind)
+    pub fn to_str(&self, ccx: &CrateContext) -> StrBuf {
+        format_strbuf!("Datum({}, {}, {:?})",
+                       ccx.tn.val_to_str(self.val),
+                       ty_to_str(ccx.tcx(), self.ty),
+                       self.kind)
     }
 
     pub fn appropriate_rvalue_mode(&self, ccx: &CrateContext) -> RvalueMode {
diff --git a/src/librustc/middle/trans/debuginfo.rs b/src/librustc/middle/trans/debuginfo.rs
index 1e56604983f5f..e185d7702ff4d 100644
--- a/src/librustc/middle/trans/debuginfo.rs
+++ b/src/librustc/middle/trans/debuginfo.rs
@@ -178,7 +178,7 @@ pub struct CrateDebugContext {
     llcontext: ContextRef,
     builder: DIBuilderRef,
     current_debug_location: Cell<DebugLocation>,
-    created_files: RefCell<HashMap<~str, DIFile>>,
+    created_files: RefCell<HashMap<StrBuf, DIFile>>,
     created_types: RefCell<HashMap<uint, DIType>>,
     created_enum_disr_types: RefCell<HashMap<ast::DefId, DIType>>,
     namespace_map: RefCell<HashMap<Vec<ast::Name>, Rc<NamespaceTreeNode>>>,
@@ -343,8 +343,8 @@ pub fn create_global_var_metadata(cx: &CrateContext,
     let linkage_name = namespace_node.mangled_name_of_contained_item(var_name);
     let var_scope = namespace_node.scope;
 
-    var_name.with_c_str(|var_name| {
-        linkage_name.with_c_str(|linkage_name| {
+    var_name.as_slice().with_c_str(|var_name| {
+        linkage_name.as_slice().with_c_str(|linkage_name| {
             unsafe {
                 llvm::LLVMDIBuilderCreateStaticVariable(DIB(cx),
                                                         var_scope,
@@ -725,7 +725,7 @@ pub fn create_function_debug_context(cx: &CrateContext,
         let containing_scope = namespace_node.scope;
         (linkage_name, containing_scope)
     } else {
-        (function_name.as_slice().to_owned(), file_metadata)
+        (function_name.as_slice().to_strbuf(), file_metadata)
     };
 
     // Clang sets this parameter to the opening brace of the function's block, so let's do this too.
@@ -734,7 +734,7 @@ pub fn create_function_debug_context(cx: &CrateContext,
     let is_local_to_unit = is_node_local_to_unit(cx, fn_ast_id);
 
     let fn_metadata = function_name.as_slice().with_c_str(|function_name| {
-                          linkage_name.with_c_str(|linkage_name| {
+                          linkage_name.as_slice().with_c_str(|linkage_name| {
             unsafe {
                 llvm::LLVMDIBuilderCreateFunction(
                     DIB(cx),
@@ -838,7 +838,8 @@ pub fn create_function_debug_context(cx: &CrateContext,
             let actual_self_type = self_type.unwrap();
             // Add self type name to <...> clause of function name
             let actual_self_type_name = ppaux::ty_to_str(cx.tcx(), actual_self_type);
-            name_to_append_suffix_to.push_str(actual_self_type_name);
+            name_to_append_suffix_to.push_str(
+                actual_self_type_name.as_slice());
 
             if generics.is_type_parameterized() {
                 name_to_append_suffix_to.push_str(",");
@@ -882,7 +883,7 @@ pub fn create_function_debug_context(cx: &CrateContext,
             let actual_type = *actual_types.get(index);
             // Add actual type name to <...> clause of function name
             let actual_type_name = ppaux::ty_to_str(cx.tcx(), actual_type);
-            name_to_append_suffix_to.push_str(actual_type_name);
+            name_to_append_suffix_to.push_str(actual_type_name.as_slice());
 
             if index != generics.ty_params.len() - 1 {
                 name_to_append_suffix_to.push_str(",");
@@ -1107,7 +1108,7 @@ fn file_metadata(cx: &CrateContext, full_path: &str) -> DIFile {
         });
 
     let mut created_files = debug_context(cx).created_files.borrow_mut();
-    created_files.insert(full_path.to_owned(), file_metadata);
+    created_files.insert(full_path.to_strbuf(), file_metadata);
     return file_metadata;
 }
 
@@ -1182,7 +1183,7 @@ fn pointer_type_metadata(cx: &CrateContext,
     let pointer_llvm_type = type_of::type_of(cx, pointer_type);
     let (pointer_size, pointer_align) = size_and_align_of(cx, pointer_llvm_type);
     let name = ppaux::ty_to_str(cx.tcx(), pointer_type);
-    let ptr_metadata = name.with_c_str(|name| {
+    let ptr_metadata = name.as_slice().with_c_str(|name| {
         unsafe {
             llvm::LLVMDIBuilderCreatePointerType(
                 DIB(cx),
@@ -1232,9 +1233,9 @@ impl StructMemberDescriptionFactory {
                                   -> Vec<MemberDescription> {
         self.fields.iter().map(|field| {
             let name = if field.ident.name == special_idents::unnamed_field.name {
-                "".to_owned()
+                "".to_strbuf()
             } else {
-                token::get_ident(field.ident).get().to_str()
+                token::get_ident(field.ident).get().to_strbuf()
             };
 
             MemberDescription {
@@ -1263,7 +1264,7 @@ fn prepare_struct_metadata(cx: &CrateContext,
 
     let struct_metadata_stub = create_struct_stub(cx,
                                                   struct_llvm_type,
-                                                  struct_name,
+                                                  struct_name.as_slice(),
                                                   containing_scope,
                                                   file_metadata,
                                                   definition_span);
@@ -1335,7 +1336,7 @@ impl TupleMemberDescriptionFactory {
                                   -> Vec<MemberDescription> {
         self.component_types.iter().map(|&component_type| {
             MemberDescription {
-                name: "".to_owned(),
+                name: "".to_strbuf(),
                 llvm_type: type_of::type_of(cx, component_type),
                 type_metadata: type_metadata(cx, component_type, self.span),
                 offset: ComputedMemberOffset,
@@ -1359,7 +1360,7 @@ fn prepare_tuple_metadata(cx: &CrateContext,
         cache_id: cache_id_for_type(tuple_type),
         metadata_stub: create_struct_stub(cx,
                                           tuple_llvm_type,
-                                          tuple_name,
+                                          tuple_name.as_slice(),
                                           file_metadata,
                                           file_metadata,
                                           span),
@@ -1413,7 +1414,7 @@ impl GeneralMemberDescriptionFactory {
                                               self.file_metadata,
                                               codemap::DUMMY_SP);
                 MemberDescription {
-                    name: "".to_owned(),
+                    name: "".to_strbuf(),
                     llvm_type: variant_llvm_type,
                     type_metadata: variant_type_metadata,
                     offset: FixedMemberOffset { bytes: 0 },
@@ -1423,7 +1424,7 @@ impl GeneralMemberDescriptionFactory {
 }
 
 struct EnumVariantMemberDescriptionFactory {
-    args: Vec<(~str, ty::t)> ,
+    args: Vec<(StrBuf, ty::t)> ,
     discriminant_type_metadata: Option<DIType>,
     span: Span,
 }
@@ -1433,7 +1434,7 @@ impl EnumVariantMemberDescriptionFactory {
                                   -> Vec<MemberDescription> {
         self.args.iter().enumerate().map(|(i, &(ref name, ty))| {
             MemberDescription {
-                name: name.to_str(),
+                name: name.to_strbuf(),
                 llvm_type: type_of::type_of(cx, ty),
                 type_metadata: match self.discriminant_type_metadata {
                     Some(metadata) if i == 0 => metadata,
@@ -1491,9 +1492,9 @@ fn describe_enum_variant(cx: &CrateContext,
     }
 
     // Build an array of (field name, field type) pairs to be captured in the factory closure.
-    let args: Vec<(~str, ty::t)> = arg_names.iter()
+    let args: Vec<(StrBuf, ty::t)> = arg_names.iter()
         .zip(struct_def.fields.iter())
-        .map(|(s, &t)| (s.to_str(), t))
+        .map(|(s, &t)| (s.to_strbuf(), t))
         .collect();
 
     let member_description_factory =
@@ -1520,13 +1521,14 @@ fn prepare_enum_metadata(cx: &CrateContext,
     // For empty enums there is an early exit. Just describe it as an empty struct with the
     // appropriate type name
     if ty::type_is_empty(cx.tcx(), enum_type) {
-        let empty_type_metadata = composite_type_metadata(cx,
-                                                          Type::nil(cx),
-                                                          enum_name,
-                                                          [],
-                                                          containing_scope,
-                                                          file_metadata,
-                                                          definition_span);
+        let empty_type_metadata = composite_type_metadata(
+            cx,
+            Type::nil(cx),
+            enum_name.as_slice(),
+            [],
+            containing_scope,
+            file_metadata,
+            definition_span);
 
         return FinalMetadata(empty_type_metadata);
     }
@@ -1621,8 +1623,8 @@ fn prepare_enum_metadata(cx: &CrateContext,
             let (enum_type_size, enum_type_align) = size_and_align_of(cx, enum_llvm_type);
             let unique_id = generate_unique_type_id("DI_ENUM_");
 
-            let enum_metadata = enum_name.with_c_str(|enum_name| {
-                unique_id.with_c_str(|unique_id| {
+            let enum_metadata = enum_name.as_slice().with_c_str(|enum_name| {
+                unique_id.as_slice().with_c_str(|unique_id| {
                     unsafe {
                         llvm::LLVMDIBuilderCreateUnionType(
                         DIB(cx),
@@ -1694,7 +1696,7 @@ enum MemberOffset {
 }
 
 struct MemberDescription {
-    name: ~str,
+    name: StrBuf,
     llvm_type: Type,
     type_metadata: DIType,
     offset: MemberOffset,
@@ -1764,7 +1766,7 @@ fn set_members_of_composite_type(cx: &CrateContext,
                 ComputedMemberOffset => machine::llelement_offset(cx, composite_llvm_type, i)
             };
 
-            member_description.name.with_c_str(|member_name| {
+            member_description.name.as_slice().with_c_str(|member_name| {
                 unsafe {
                     llvm::LLVMDIBuilderCreateMemberType(
                         DIB(cx),
@@ -1806,7 +1808,7 @@ fn create_struct_stub(cx: &CrateContext,
 
     return unsafe {
         struct_type_name.with_c_str(|name| {
-            unique_id.with_c_str(|unique_id| {
+            unique_id.as_slice().with_c_str(|unique_id| {
                 // LLVMDIBuilderCreateStructType() wants an empty array. A null pointer will lead to
                 // hard to trace and debug LLVM assertions later on in llvm/lib/IR/Value.cpp
                 let empty_array = create_DIArray(DIB(cx), []);
@@ -1853,31 +1855,31 @@ fn boxed_type_metadata(cx: &CrateContext,
 
     let member_descriptions = [
         MemberDescription {
-            name: "refcnt".to_owned(),
+            name: "refcnt".to_strbuf(),
             llvm_type: *member_llvm_types.get(0),
             type_metadata: type_metadata(cx, int_type, codemap::DUMMY_SP),
             offset: ComputedMemberOffset,
         },
         MemberDescription {
-            name: "drop_glue".to_owned(),
+            name: "drop_glue".to_strbuf(),
             llvm_type: *member_llvm_types.get(1),
             type_metadata: nil_pointer_type_metadata,
             offset: ComputedMemberOffset,
         },
         MemberDescription {
-            name: "prev".to_owned(),
+            name: "prev".to_strbuf(),
             llvm_type: *member_llvm_types.get(2),
             type_metadata: nil_pointer_type_metadata,
             offset: ComputedMemberOffset,
         },
         MemberDescription {
-            name: "next".to_owned(),
+            name: "next".to_strbuf(),
             llvm_type: *member_llvm_types.get(3),
             type_metadata: nil_pointer_type_metadata,
             offset: ComputedMemberOffset,
         },
         MemberDescription {
-            name: "val".to_owned(),
+            name: "val".to_strbuf(),
             llvm_type: *member_llvm_types.get(4),
             type_metadata: content_type_metadata,
             offset: ComputedMemberOffset,
@@ -1964,19 +1966,19 @@ fn vec_metadata(cx: &CrateContext,
 
     let member_descriptions = [
         MemberDescription {
-            name: "fill".to_owned(),
+            name: "fill".to_strbuf(),
             llvm_type: *member_llvm_types.get(0),
             type_metadata: int_type_metadata,
             offset: ComputedMemberOffset,
         },
         MemberDescription {
-            name: "alloc".to_owned(),
+            name: "alloc".to_strbuf(),
             llvm_type: *member_llvm_types.get(1),
             type_metadata: int_type_metadata,
             offset: ComputedMemberOffset,
         },
         MemberDescription {
-            name: "elements".to_owned(),
+            name: "elements".to_strbuf(),
             llvm_type: *member_llvm_types.get(2),
             type_metadata: array_type_metadata,
             offset: ComputedMemberOffset,
@@ -2021,13 +2023,13 @@ fn vec_slice_metadata(cx: &CrateContext,
 
     let member_descriptions = [
         MemberDescription {
-            name: "data_ptr".to_owned(),
+            name: "data_ptr".to_strbuf(),
             llvm_type: *member_llvm_types.get(0),
             type_metadata: type_metadata(cx, data_ptr_type, span),
             offset: ComputedMemberOffset,
         },
         MemberDescription {
-            name: "length".to_owned(),
+            name: "length".to_strbuf(),
             llvm_type: *member_llvm_types.get(1),
             type_metadata: type_metadata(cx, ty::mk_uint(), span),
             offset: ComputedMemberOffset,
@@ -2042,7 +2044,7 @@ fn vec_slice_metadata(cx: &CrateContext,
     return composite_type_metadata(
         cx,
         slice_llvm_type,
-        slice_type_name,
+        slice_type_name.as_slice(),
         member_descriptions,
         file_metadata,
         file_metadata,
@@ -2099,11 +2101,15 @@ fn trait_metadata(cx: &CrateContext,
     // the trait's methods.
     let last = ty::with_path(cx.tcx(), def_id, |mut path| path.last().unwrap());
     let ident_string = token::get_name(last.name());
-    let name = ppaux::trait_store_to_str(cx.tcx(), trait_store) +
-               ident_string.get();
+    let mut name = ppaux::trait_store_to_str(cx.tcx(), trait_store);
+    name.push_str(ident_string.get());
     // Add type and region parameters
-    let name = ppaux::parameterized(cx.tcx(), name, &substs.regions,
-                                    substs.tps.as_slice(), def_id, true);
+    let name = ppaux::parameterized(cx.tcx(),
+                                    name.as_slice(),
+                                    &substs.regions,
+                                    substs.tps.as_slice(),
+                                    def_id,
+                                    true);
 
     let (containing_scope, definition_span) = get_namespace_and_span_for_item(cx, def_id);
 
@@ -2114,7 +2120,7 @@ fn trait_metadata(cx: &CrateContext,
 
     composite_type_metadata(cx,
                             trait_llvm_type,
-                            name,
+                            name.as_slice(),
                             [],
                             containing_scope,
                             file_metadata,
@@ -2136,7 +2142,8 @@ fn type_metadata(cx: &CrateContext,
                                       pointer_type: ty::t,
                                       type_in_box: ty::t)
                                    -> DIType {
-        let content_type_name: &str = ppaux::ty_to_str(cx.tcx(), type_in_box);
+        let content_type_name = ppaux::ty_to_str(cx.tcx(), type_in_box);
+        let content_type_name = content_type_name.as_slice();
         let content_llvm_type = type_of::type_of(cx, type_in_box);
         let content_type_metadata = type_metadata(
             cx,
@@ -2296,10 +2303,12 @@ fn cache_id_for_type(t: ty::t) -> uint {
 
 // Used to avoid LLVM metadata uniquing problems. See `create_struct_stub()` and
 // `prepare_enum_metadata()`.
-fn generate_unique_type_id(prefix: &'static str) -> ~str {
+fn generate_unique_type_id(prefix: &'static str) -> StrBuf {
     unsafe {
         static mut unique_id_counter: atomics::AtomicUint = atomics::INIT_ATOMIC_UINT;
-        format!("{}{}", prefix, unique_id_counter.fetch_add(1, atomics::SeqCst))
+        format_strbuf!("{}{}",
+                       prefix,
+                       unique_id_counter.fetch_add(1, atomics::SeqCst))
     }
 }
 
@@ -2796,7 +2805,7 @@ fn populate_scope_map(cx: &CrateContext,
             ast::ExprInlineAsm(ast::InlineAsm { inputs: ref inputs,
                                                 outputs: ref outputs,
                                                 .. }) => {
-                // inputs, outputs: ~[(~str, @expr)]
+                // inputs, outputs: ~[(StrBuf, @expr)]
                 for &(_, exp) in inputs.iter() {
                     walk_expr(cx, exp, scope_stack, scope_map);
                 }
@@ -2821,7 +2830,7 @@ struct NamespaceTreeNode {
 }
 
 impl NamespaceTreeNode {
-    fn mangled_name_of_contained_item(&self, item_name: &str) -> ~str {
+    fn mangled_name_of_contained_item(&self, item_name: &str) -> StrBuf {
         fn fill_nested(node: &NamespaceTreeNode, output: &mut StrBuf) {
             match node.parent {
                 Some(ref parent) => fill_nested(&*parent.upgrade().unwrap(), output),
@@ -2837,7 +2846,7 @@ impl NamespaceTreeNode {
         name.push_str(format!("{}", item_name.len()));
         name.push_str(item_name);
         name.push_char('E');
-        name.into_owned()
+        name
     }
 }
 
diff --git a/src/librustc/middle/trans/expr.rs b/src/librustc/middle/trans/expr.rs
index 463aa67ac90f5..d3be50735be2a 100644
--- a/src/librustc/middle/trans/expr.rs
+++ b/src/librustc/middle/trans/expr.rs
@@ -86,10 +86,10 @@ pub enum Dest {
 }
 
 impl Dest {
-    pub fn to_str(&self, ccx: &CrateContext) -> ~str {
+    pub fn to_str(&self, ccx: &CrateContext) -> StrBuf {
         match *self {
-            SaveIn(v) => format!("SaveIn({})", ccx.tn.val_to_str(v)),
-            Ignore => "Ignore".to_owned()
+            SaveIn(v) => format_strbuf!("SaveIn({})", ccx.tn.val_to_str(v)),
+            Ignore => "Ignore".to_strbuf()
         }
     }
 }
@@ -545,7 +545,7 @@ fn trans_def<'a>(bcx: &'a Block<'a>,
                         let symbol = csearch::get_symbol(
                             &bcx.ccx().sess().cstore,
                             did);
-                        let llval = symbol.with_c_str(|buf| {
+                        let llval = symbol.as_slice().with_c_str(|buf| {
                                 llvm::LLVMAddGlobal(bcx.ccx().llmod,
                                                     llty.to_ref(),
                                                     buf)
diff --git a/src/librustc/middle/trans/foreign.rs b/src/librustc/middle/trans/foreign.rs
index 0a2bf60bf04e2..36f4eb1fd11dd 100644
--- a/src/librustc/middle/trans/foreign.rs
+++ b/src/librustc/middle/trans/foreign.rs
@@ -445,7 +445,7 @@ pub fn trans_foreign_mod(ccx: &CrateContext, foreign_mod: &ast::ForeignMod) {
 
         let lname = link_name(foreign_item);
         ccx.item_symbols.borrow_mut().insert(foreign_item.id,
-                                             lname.get().to_owned());
+                                             lname.get().to_strbuf());
     }
 }
 
@@ -476,7 +476,7 @@ pub fn trans_foreign_mod(ccx: &CrateContext, foreign_mod: &ast::ForeignMod) {
 
 pub fn register_rust_fn_with_foreign_abi(ccx: &CrateContext,
                                          sp: Span,
-                                         sym: ~str,
+                                         sym: StrBuf,
                                          node_id: ast::NodeId)
                                          -> ValueRef {
     let _icx = push_ctxt("foreign::register_foreign_fn");
@@ -553,7 +553,7 @@ pub fn trans_rust_fn_with_foreign_abi(ccx: &CrateContext,
                                                false,
                                                f.sig.inputs.as_slice(),
                                                f.sig.output,
-                                               ps);
+                                               ps.as_slice());
         base::set_llvm_fn_attrs(attrs, llfn);
         base::trans_fn(ccx, decl, body, llfn, None, id, []);
         llfn
diff --git a/src/librustc/middle/trans/glue.rs b/src/librustc/middle/trans/glue.rs
index 4f03ec0567cfb..8869bd010b294 100644
--- a/src/librustc/middle/trans/glue.rs
+++ b/src/librustc/middle/trans/glue.rs
@@ -203,7 +203,7 @@ fn make_visit_glue<'a>(bcx: &'a Block<'a>, v: ValueRef, t: ty::t)
                                                                  ty::ReStatic) {
         Ok(pair) => pair,
         Err(s) => {
-            bcx.tcx().sess.fatal(s);
+            bcx.tcx().sess.fatal(s.as_slice());
         }
     };
     let v = PointerCast(bcx, v, type_of(bcx.ccx(), object_ty).ptr_to());
@@ -413,14 +413,15 @@ pub fn declare_tydesc(ccx: &CrateContext, t: ty::t) -> tydesc_info {
     let llalign = llalign_of(ccx, llty);
     let name = mangle_internal_name_by_type_and_seq(ccx, t, "tydesc");
     debug!("+++ declare_tydesc {} {}", ppaux::ty_to_str(ccx.tcx(), t), name);
-    let gvar = name.with_c_str(|buf| {
+    let gvar = name.as_slice().with_c_str(|buf| {
         unsafe {
             llvm::LLVMAddGlobal(ccx.llmod, ccx.tydesc_type().to_ref(), buf)
         }
     });
     note_unique_llvm_symbol(ccx, name);
 
-    let ty_name = token::intern_and_get_ident(ppaux::ty_to_str(ccx.tcx(), t));
+    let ty_name = token::intern_and_get_ident(
+        ppaux::ty_to_str(ccx.tcx(), t).as_slice());
     let ty_name = C_str_slice(ccx, ty_name);
 
     debug!("--- declare_tydesc {}", ppaux::ty_to_str(ccx.tcx(), t));
@@ -439,7 +440,10 @@ fn declare_generic_glue(ccx: &CrateContext, t: ty::t, llfnty: Type,
     let _icx = push_ctxt("declare_generic_glue");
     let fn_nm = mangle_internal_name_by_type_and_seq(ccx, t, "glue_".to_owned() + name);
     debug!("{} is for type {}", fn_nm, ppaux::ty_to_str(ccx.tcx(), t));
-    let llfn = decl_cdecl_fn(ccx.llmod, fn_nm, llfnty, ty::mk_nil());
+    let llfn = decl_cdecl_fn(ccx.llmod,
+                             fn_nm.as_slice(),
+                             llfnty,
+                             ty::mk_nil());
     note_unique_llvm_symbol(ccx, fn_nm);
     return llfn;
 }
@@ -452,7 +456,9 @@ fn make_generic_glue(ccx: &CrateContext,
                      name: &str)
                      -> ValueRef {
     let _icx = push_ctxt("make_generic_glue");
-    let glue_name = format!("glue {} {}", name, ty_to_short_str(ccx.tcx(), t));
+    let glue_name = format_strbuf!("glue {} {}",
+                                   name,
+                                   ty_to_short_str(ccx.tcx(), t));
     let _s = StatRecorder::new(ccx, glue_name);
 
     let arena = TypedArena::new();
diff --git a/src/librustc/middle/trans/llrepr.rs b/src/librustc/middle/trans/llrepr.rs
index c84e4db768696..c5a4d136ab92f 100644
--- a/src/librustc/middle/trans/llrepr.rs
+++ b/src/librustc/middle/trans/llrepr.rs
@@ -13,24 +13,24 @@ use middle::trans::type_::Type;
 use lib::llvm::ValueRef;
 
 pub trait LlvmRepr {
-    fn llrepr(&self, ccx: &CrateContext) -> ~str;
+    fn llrepr(&self, ccx: &CrateContext) -> StrBuf;
 }
 
 impl<'a, T:LlvmRepr> LlvmRepr for &'a [T] {
-    fn llrepr(&self, ccx: &CrateContext) -> ~str {
-        let reprs: Vec<~str> = self.iter().map(|t| t.llrepr(ccx)).collect();
-        format!("[{}]", reprs.connect(","))
+    fn llrepr(&self, ccx: &CrateContext) -> StrBuf {
+        let reprs: Vec<StrBuf> = self.iter().map(|t| t.llrepr(ccx)).collect();
+        format_strbuf!("[{}]", reprs.connect(","))
     }
 }
 
 impl LlvmRepr for Type {
-    fn llrepr(&self, ccx: &CrateContext) -> ~str {
+    fn llrepr(&self, ccx: &CrateContext) -> StrBuf {
         ccx.tn.type_to_str(*self)
     }
 }
 
 impl LlvmRepr for ValueRef {
-    fn llrepr(&self, ccx: &CrateContext) -> ~str {
+    fn llrepr(&self, ccx: &CrateContext) -> StrBuf {
         ccx.tn.val_to_str(*self)
     }
 }
diff --git a/src/librustc/middle/trans/monomorphize.rs b/src/librustc/middle/trans/monomorphize.rs
index 69f1dcbc67cd4..bc3a0c0073f27 100644
--- a/src/librustc/middle/trans/monomorphize.rs
+++ b/src/librustc/middle/trans/monomorphize.rs
@@ -109,9 +109,10 @@ pub fn monomorphic_fn(ccx: &CrateContext,
         ccx.sess(),
         ccx.tcx.map.find(fn_id.node),
         || {
-            (format!("while monomorphizing {:?}, couldn't find it in the \
-                      item map (may have attempted to monomorphize an item \
-                      defined in a different crate?)", fn_id)).to_strbuf()
+            format_strbuf!("while monomorphizing {:?}, couldn't find it in \
+                            the item map (may have attempted to monomorphize \
+                            an item defined in a different crate?)",
+                           fn_id)
         });
 
     match map_node {
@@ -212,9 +213,11 @@ pub fn monomorphic_fn(ccx: &CrateContext,
     // This shouldn't need to option dance.
     let mut hash_id = Some(hash_id);
     let mk_lldecl = || {
-        let lldecl = decl_internal_rust_fn(ccx, false,
+        let lldecl = decl_internal_rust_fn(ccx,
+                                           false,
                                            f.sig.inputs.as_slice(),
-                                           f.sig.output, s);
+                                           f.sig.output,
+                                           s.as_slice());
         ccx.monomorphized.borrow_mut().insert(hash_id.take_unwrap(), lldecl);
         lldecl
     };
diff --git a/src/librustc/middle/trans/reflect.rs b/src/librustc/middle/trans/reflect.rs
index 307654f1d9699..206fc07cd864e 100644
--- a/src/librustc/middle/trans/reflect.rs
+++ b/src/librustc/middle/trans/reflect.rs
@@ -254,8 +254,9 @@ impl<'a, 'b> Reflector<'a, 'b> {
               }
 
               let extra = (vec!(
-                  self.c_slice(token::intern_and_get_ident(ty_to_str(tcx,
-                                                                     t))),
+                  self.c_slice(
+                      token::intern_and_get_ident(ty_to_str(tcx,
+                                                            t).as_slice())),
                   self.c_bool(named_fields),
                   self.c_uint(fields.len())
               )).append(self.c_size_and_align(t).as_slice());
@@ -288,7 +289,11 @@ impl<'a, 'b> Reflector<'a, 'b> {
                 let sym = mangle_internal_name_by_path_and_seq(
                     ast_map::Values([].iter()).chain(None), "get_disr");
 
-                let llfdecl = decl_internal_rust_fn(ccx, false, [opaqueptrty], ty::mk_u64(), sym);
+                let llfdecl = decl_internal_rust_fn(ccx,
+                                                    false,
+                                                    [opaqueptrty],
+                                                    ty::mk_u64(),
+                                                    sym.as_slice());
                 let arena = TypedArena::new();
                 let fcx = new_fn_ctxt(ccx, llfdecl, -1, false,
                                       ty::mk_u64(), None, None, &arena);
@@ -344,7 +349,8 @@ impl<'a, 'b> Reflector<'a, 'b> {
 
           ty::ty_trait(..) => {
               let extra = [
-                  self.c_slice(token::intern_and_get_ident(ty_to_str(tcx, t)))
+                  self.c_slice(token::intern_and_get_ident(
+                          ty_to_str(tcx, t).as_slice()))
               ];
               self.visit("trait", extra);
           }
diff --git a/src/librustc/middle/trans/tvec.rs b/src/librustc/middle/trans/tvec.rs
index 48179abc052ec..8ed3b76d6523d 100644
--- a/src/librustc/middle/trans/tvec.rs
+++ b/src/librustc/middle/trans/tvec.rs
@@ -73,13 +73,13 @@ pub struct VecTypes {
 }
 
 impl VecTypes {
-    pub fn to_str(&self, ccx: &CrateContext) -> ~str {
-        format!("VecTypes \\{unit_ty={}, llunit_ty={}, llunit_size={}, \
-                 llunit_alloc_size={}\\}",
-             ty_to_str(ccx.tcx(), self.unit_ty),
-             ccx.tn.type_to_str(self.llunit_ty),
-             ccx.tn.val_to_str(self.llunit_size),
-             self.llunit_alloc_size)
+    pub fn to_str(&self, ccx: &CrateContext) -> StrBuf {
+        format_strbuf!("VecTypes \\{unit_ty={}, llunit_ty={}, \
+                        llunit_size={}, llunit_alloc_size={}\\}",
+                       ty_to_str(ccx.tcx(), self.unit_ty),
+                       ccx.tn.type_to_str(self.llunit_ty),
+                       ccx.tn.val_to_str(self.llunit_size),
+                       self.llunit_alloc_size)
     }
 }
 
diff --git a/src/librustc/middle/trans/type_of.rs b/src/librustc/middle/trans/type_of.rs
index 7e3890cec8562..9d13fa56e1e73 100644
--- a/src/librustc/middle/trans/type_of.rs
+++ b/src/librustc/middle/trans/type_of.rs
@@ -206,7 +206,7 @@ pub fn type_of(cx: &CrateContext, t: ty::t) -> Type {
         // of the enum's variants refers to the enum itself.
         let repr = adt::represent_type(cx, t);
         let name = llvm_type_name(cx, an_enum, did, substs.tps.as_slice());
-        adt::incomplete_type_of(cx, &*repr, name)
+        adt::incomplete_type_of(cx, &*repr, name.as_slice())
       }
       ty::ty_box(typ) => {
           Type::at_box(cx, type_of(cx, typ)).ptr_to()
@@ -264,7 +264,7 @@ pub fn type_of(cx: &CrateContext, t: ty::t) -> Type {
                                         a_struct,
                                         did,
                                         substs.tps.as_slice());
-              adt::incomplete_type_of(cx, &*repr, name)
+              adt::incomplete_type_of(cx, &*repr, name.as_slice())
           }
       }
 
@@ -301,18 +301,24 @@ pub enum named_ty { a_struct, an_enum }
 pub fn llvm_type_name(cx: &CrateContext,
                       what: named_ty,
                       did: ast::DefId,
-                      tps: &[ty::t]) -> ~str {
+                      tps: &[ty::t])
+                      -> StrBuf {
     let name = match what {
         a_struct => { "struct" }
         an_enum => { "enum" }
     };
-    let tstr = ppaux::parameterized(cx.tcx(), ty::item_path_str(cx.tcx(), did),
-                                    &ty::NonerasedRegions(OwnedSlice::empty()),
-                                    tps, did, false);
+    let tstr = ppaux::parameterized(cx.tcx(),
+                                    ty::item_path_str(cx.tcx(),
+                                                      did).as_slice(),
+                                    &ty::NonerasedRegions(
+                                        OwnedSlice::empty()),
+                                    tps,
+                                    did,
+                                    false);
     if did.krate == 0 {
-        format!("{}.{}", name, tstr)
+        format_strbuf!("{}.{}", name, tstr)
     } else {
-        format!("{}.{}[\\#{}]", name, tstr, did.krate)
+        format_strbuf!("{}.{}[\\#{}]", name, tstr, did.krate)
     }
 }
 
diff --git a/src/librustc/middle/ty.rs b/src/librustc/middle/ty.rs
index f37a4ab0aaa4a..b6f8f33b719cc 100644
--- a/src/librustc/middle/ty.rs
+++ b/src/librustc/middle/ty.rs
@@ -278,7 +278,7 @@ pub struct ctxt {
     pub freevars: RefCell<freevars::freevar_map>,
     pub tcache: type_cache,
     pub rcache: creader_cache,
-    pub short_names_cache: RefCell<HashMap<t, ~str>>,
+    pub short_names_cache: RefCell<HashMap<t, StrBuf>>,
     pub needs_unwind_cleanup_cache: RefCell<HashMap<t, bool>>,
     pub tc_cache: RefCell<HashMap<uint, TypeContents>>,
     pub ast_ty_to_ty_cache: RefCell<NodeMap<ast_ty_to_ty_cache_entry>>,
@@ -1538,7 +1538,7 @@ pub fn substs_is_noop(substs: &substs) -> bool {
         substs.self_ty.is_none()
 }
 
-pub fn substs_to_str(cx: &ctxt, substs: &substs) -> ~str {
+pub fn substs_to_str(cx: &ctxt, substs: &substs) -> StrBuf {
     substs.repr(cx)
 }
 
@@ -3189,7 +3189,9 @@ pub fn field_idx_strict(tcx: &ctxt, name: ast::Name, fields: &[field])
     tcx.sess.bug(format!(
         "no field named `{}` found in the list of fields `{:?}`",
         token::get_name(name),
-        fields.iter().map(|f| token::get_ident(f.ident).get().to_str()).collect::<Vec<~str>>()));
+        fields.iter()
+              .map(|f| token::get_ident(f.ident).get().to_strbuf())
+              .collect::<Vec<StrBuf>>()));
 }
 
 pub fn method_idx(id: ast::Ident, meths: &[Rc<Method>]) -> Option<uint> {
@@ -3212,34 +3214,38 @@ pub fn param_tys_in_type(ty: t) -> Vec<param_ty> {
     rslt
 }
 
-pub fn ty_sort_str(cx: &ctxt, t: t) -> ~str {
+pub fn ty_sort_str(cx: &ctxt, t: t) -> StrBuf {
     match get(t).sty {
         ty_nil | ty_bot | ty_bool | ty_char | ty_int(_) |
         ty_uint(_) | ty_float(_) | ty_str => {
             ::util::ppaux::ty_to_str(cx, t)
         }
 
-        ty_enum(id, _) => format!("enum {}", item_path_str(cx, id)),
-        ty_box(_) => "@-ptr".to_owned(),
-        ty_uniq(_) => "box".to_owned(),
-        ty_vec(_, _) => "vector".to_owned(),
-        ty_ptr(_) => "*-ptr".to_owned(),
-        ty_rptr(_, _) => "&-ptr".to_owned(),
-        ty_bare_fn(_) => "extern fn".to_owned(),
-        ty_closure(_) => "fn".to_owned(),
-        ty_trait(ref inner) => format!("trait {}", item_path_str(cx, inner.def_id)),
-        ty_struct(id, _) => format!("struct {}", item_path_str(cx, id)),
-        ty_tup(_) => "tuple".to_owned(),
-        ty_infer(TyVar(_)) => "inferred type".to_owned(),
-        ty_infer(IntVar(_)) => "integral variable".to_owned(),
-        ty_infer(FloatVar(_)) => "floating-point variable".to_owned(),
-        ty_param(_) => "type parameter".to_owned(),
-        ty_self(_) => "self".to_owned(),
-        ty_err => "type error".to_owned()
+        ty_enum(id, _) => format_strbuf!("enum {}", item_path_str(cx, id)),
+        ty_box(_) => "@-ptr".to_strbuf(),
+        ty_uniq(_) => "box".to_strbuf(),
+        ty_vec(_, _) => "vector".to_strbuf(),
+        ty_ptr(_) => "*-ptr".to_strbuf(),
+        ty_rptr(_, _) => "&-ptr".to_strbuf(),
+        ty_bare_fn(_) => "extern fn".to_strbuf(),
+        ty_closure(_) => "fn".to_strbuf(),
+        ty_trait(ref inner) => {
+            format_strbuf!("trait {}", item_path_str(cx, inner.def_id))
+        }
+        ty_struct(id, _) => {
+            format_strbuf!("struct {}", item_path_str(cx, id))
+        }
+        ty_tup(_) => "tuple".to_strbuf(),
+        ty_infer(TyVar(_)) => "inferred type".to_strbuf(),
+        ty_infer(IntVar(_)) => "integral variable".to_strbuf(),
+        ty_infer(FloatVar(_)) => "floating-point variable".to_strbuf(),
+        ty_param(_) => "type parameter".to_strbuf(),
+        ty_self(_) => "self".to_strbuf(),
+        ty_err => "type error".to_strbuf(),
     }
 }
 
-pub fn type_err_to_str(cx: &ctxt, err: &type_err) -> ~str {
+pub fn type_err_to_str(cx: &ctxt, err: &type_err) -> StrBuf {
     /*!
      *
      * Explains the source of a type err in a short,
@@ -3249,126 +3255,145 @@ pub fn type_err_to_str(cx: &ctxt, err: &type_err) -> ~str {
      * to present additional details, particularly when
      * it comes to lifetime-related errors. */
 
-    fn tstore_to_closure(s: &TraitStore) -> ~str {
+    fn tstore_to_closure(s: &TraitStore) -> StrBuf {
         match s {
-            &UniqTraitStore => "proc".to_owned(),
-            &RegionTraitStore(..) => "closure".to_owned()
+            &UniqTraitStore => "proc".to_strbuf(),
+            &RegionTraitStore(..) => "closure".to_strbuf()
         }
     }
 
     match *err {
-        terr_mismatch => "types differ".to_owned(),
+        terr_mismatch => "types differ".to_strbuf(),
         terr_fn_style_mismatch(values) => {
-            format!("expected {} fn but found {} fn",
-                 values.expected.to_str(), values.found.to_str())
+            format_strbuf!("expected {} fn but found {} fn",
+                           values.expected.to_str(),
+                           values.found.to_str())
         }
         terr_abi_mismatch(values) => {
-            format!("expected {} fn but found {} fn",
-                 values.expected.to_str(), values.found.to_str())
+            format_strbuf!("expected {} fn but found {} fn",
+                           values.expected.to_str(),
+                           values.found.to_str())
         }
         terr_onceness_mismatch(values) => {
-            format!("expected {} fn but found {} fn",
-                 values.expected.to_str(), values.found.to_str())
+            format_strbuf!("expected {} fn but found {} fn",
+                           values.expected.to_str(),
+                           values.found.to_str())
         }
         terr_sigil_mismatch(values) => {
-            format!("expected {}, found {}",
-                    tstore_to_closure(&values.expected),
-                    tstore_to_closure(&values.found))
-        }
-        terr_mutability => "values differ in mutability".to_owned(),
-        terr_box_mutability => "boxed values differ in mutability".to_owned(),
-        terr_vec_mutability => "vectors differ in mutability".to_owned(),
-        terr_ptr_mutability => "pointers differ in mutability".to_owned(),
-        terr_ref_mutability => "references differ in mutability".to_owned(),
+            format_strbuf!("expected {}, found {}",
+                           tstore_to_closure(&values.expected),
+                           tstore_to_closure(&values.found))
+        }
+        terr_mutability => "values differ in mutability".to_strbuf(),
+        terr_box_mutability => {
+            "boxed values differ in mutability".to_strbuf()
+        }
+        terr_vec_mutability => "vectors differ in mutability".to_strbuf(),
+        terr_ptr_mutability => "pointers differ in mutability".to_strbuf(),
+        terr_ref_mutability => "references differ in mutability".to_strbuf(),
         terr_ty_param_size(values) => {
-            format!("expected a type with {} type params \
-                  but found one with {} type params",
-                 values.expected, values.found)
+            format_strbuf!("expected a type with {} type params \
+                            but found one with {} type params",
+                           values.expected,
+                           values.found)
         }
         terr_tuple_size(values) => {
-            format!("expected a tuple with {} elements \
-                  but found one with {} elements",
-                 values.expected, values.found)
+            format_strbuf!("expected a tuple with {} elements \
+                            but found one with {} elements",
+                           values.expected,
+                           values.found)
         }
         terr_record_size(values) => {
-            format!("expected a record with {} fields \
-                  but found one with {} fields",
-                 values.expected, values.found)
+            format_strbuf!("expected a record with {} fields \
+                            but found one with {} fields",
+                           values.expected,
+                           values.found)
         }
         terr_record_mutability => {
-            "record elements differ in mutability".to_owned()
+            "record elements differ in mutability".to_strbuf()
         }
         terr_record_fields(values) => {
-            format!("expected a record with field `{}` but found one with field \
-                  `{}`",
-                 token::get_ident(values.expected),
-                 token::get_ident(values.found))
+            format_strbuf!("expected a record with field `{}` but found one \
+                            with field `{}`",
+                           token::get_ident(values.expected),
+                           token::get_ident(values.found))
+        }
+        terr_arg_count => {
+            "incorrect number of function parameters".to_strbuf()
         }
-        terr_arg_count => "incorrect number of function parameters".to_owned(),
         terr_regions_does_not_outlive(..) => {
-            format!("lifetime mismatch")
+            "lifetime mismatch".to_strbuf()
         }
         terr_regions_not_same(..) => {
-            format!("lifetimes are not the same")
+            "lifetimes are not the same".to_strbuf()
         }
         terr_regions_no_overlap(..) => {
-            format!("lifetimes do not intersect")
+            "lifetimes do not intersect".to_strbuf()
         }
         terr_regions_insufficiently_polymorphic(br, _) => {
-            format!("expected bound lifetime parameter {}, \
-                  but found concrete lifetime",
-                 bound_region_ptr_to_str(cx, br))
+            format_strbuf!("expected bound lifetime parameter {}, \
+                            but found concrete lifetime",
+                           bound_region_ptr_to_str(cx, br))
         }
         terr_regions_overly_polymorphic(br, _) => {
-            format!("expected concrete lifetime, \
-                  but found bound lifetime parameter {}",
-                 bound_region_ptr_to_str(cx, br))
+            format_strbuf!("expected concrete lifetime, \
+                            but found bound lifetime parameter {}",
+                           bound_region_ptr_to_str(cx, br))
         }
         terr_trait_stores_differ(_, ref values) => {
-            format!("trait storage differs: expected `{}` but found `{}`",
-                 trait_store_to_str(cx, (*values).expected),
-                 trait_store_to_str(cx, (*values).found))
+            format_strbuf!("trait storage differs: expected `{}` but found \
+                            `{}`",
+                           trait_store_to_str(cx, (*values).expected),
+                           trait_store_to_str(cx, (*values).found))
         }
         terr_sorts(values) => {
-            format!("expected {} but found {}",
-                 ty_sort_str(cx, values.expected),
-                 ty_sort_str(cx, values.found))
+            format_strbuf!("expected {} but found {}",
+                           ty_sort_str(cx, values.expected),
+                           ty_sort_str(cx, values.found))
         }
         terr_traits(values) => {
-            format!("expected trait `{}` but found trait `{}`",
-                 item_path_str(cx, values.expected),
-                 item_path_str(cx, values.found))
+            format_strbuf!("expected trait `{}` but found trait `{}`",
+                           item_path_str(cx, values.expected),
+                           item_path_str(cx, values.found))
         }
         terr_builtin_bounds(values) => {
             if values.expected.is_empty() {
-                format!("expected no bounds but found `{}`",
-                     values.found.user_string(cx))
+                format_strbuf!("expected no bounds but found `{}`",
+                               values.found.user_string(cx))
             } else if values.found.is_empty() {
-                format!("expected bounds `{}` but found no bounds",
-                     values.expected.user_string(cx))
+                format_strbuf!("expected bounds `{}` but found no bounds",
+                               values.expected.user_string(cx))
             } else {
-                format!("expected bounds `{}` but found bounds `{}`",
-                     values.expected.user_string(cx),
-                     values.found.user_string(cx))
+                format_strbuf!("expected bounds `{}` but found bounds `{}`",
+                               values.expected.user_string(cx),
+                               values.found.user_string(cx))
             }
         }
         terr_integer_as_char => {
-            format!("expected an integral type but found `char`")
+            "expected an integral type but found `char`".to_strbuf()
         }
         terr_int_mismatch(ref values) => {
-            format!("expected `{}` but found `{}`",
-                 values.expected.to_str(),
-                 values.found.to_str())
+            format_strbuf!("expected `{}` but found `{}`",
+                           values.expected.to_str(),
+                           values.found.to_str())
         }
         terr_float_mismatch(ref values) => {
-            format!("expected `{}` but found `{}`",
-                 values.expected.to_str(),
-                 values.found.to_str())
+            format_strbuf!("expected `{}` but found `{}`",
+                           values.expected.to_str(),
+                           values.found.to_str())
         }
         terr_variadic_mismatch(ref values) => {
-            format!("expected {} fn but found {} function",
-                    if values.expected { "variadic" } else { "non-variadic" },
-                    if values.found { "variadic" } else { "non-variadic" })
+            format_strbuf!("expected {} fn but found {} function",
+                           if values.expected {
+                                "variadic"
+                           } else {
+                                "non-variadic"
+                           },
+                           if values.found {
+                               "variadic"
+                           } else {
+                               "non-variadic"
+                           })
         }
     }
 }
@@ -3665,8 +3690,8 @@ pub fn substd_enum_variants(cx: &ctxt,
     }).collect()
 }
 
-pub fn item_path_str(cx: &ctxt, id: ast::DefId) -> ~str {
-    with_path(cx, id, |path| ast_map::path_to_str(path)).to_owned()
+pub fn item_path_str(cx: &ctxt, id: ast::DefId) -> StrBuf {
+    with_path(cx, id, |path| ast_map::path_to_str(path)).to_strbuf()
 }
 
 pub enum DtorKind {
@@ -4231,14 +4256,14 @@ pub fn each_bound_trait_and_supertraits(tcx: &ctxt,
     return true;
 }
 
-pub fn get_tydesc_ty(tcx: &ctxt) -> Result<t, ~str> {
+pub fn get_tydesc_ty(tcx: &ctxt) -> Result<t, StrBuf> {
     tcx.lang_items.require(TyDescStructLangItem).map(|tydesc_lang_item| {
         tcx.intrinsic_defs.borrow().find_copy(&tydesc_lang_item)
             .expect("Failed to resolve TyDesc")
     })
 }
 
-pub fn get_opaque_ty(tcx: &ctxt) -> Result<t, ~str> {
+pub fn get_opaque_ty(tcx: &ctxt) -> Result<t, StrBuf> {
     tcx.lang_items.require(OpaqueStructLangItem).map(|opaque_lang_item| {
         tcx.intrinsic_defs.borrow().find_copy(&opaque_lang_item)
             .expect("Failed to resolve Opaque")
@@ -4246,7 +4271,7 @@ pub fn get_opaque_ty(tcx: &ctxt) -> Result<t, ~str> {
 }
 
 pub fn visitor_object_ty(tcx: &ctxt,
-                         region: ty::Region) -> Result<(Rc<TraitRef>, t), ~str> {
+                         region: ty::Region) -> Result<(Rc<TraitRef>, t), StrBuf> {
     let trait_lang_item = match tcx.lang_items.require(TyVisitorTraitLangItem) {
         Ok(id) => id,
         Err(s) => { return Err(s); }
diff --git a/src/librustc/middle/typeck/check/_match.rs b/src/librustc/middle/typeck/check/_match.rs
index e6a6a370b1330..740539cbddd7d 100644
--- a/src/librustc/middle/typeck/check/_match.rs
+++ b/src/librustc/middle/typeck/check/_match.rs
@@ -166,11 +166,15 @@ pub fn check_pat_variant(pcx: &pat_ctxt, pat: &ast::Pat, path: &ast::Path,
                     // See [Note-Type-error-reporting] in middle/typeck/infer/mod.rs
                     fcx.infcx().type_error_message_str_with_expected(pat.span,
                                                        |expected, actual| {
-                                                       expected.map_or("".to_owned(), |e| {
-                        format!("mismatched types: expected `{}` but found {}",
-                             e, actual)})},
-                             Some(expected), "a structure pattern".to_owned(),
-                             None);
+                       expected.map_or("".to_strbuf(), |e| {
+                        format_strbuf!("mismatched types: expected `{}` but \
+                                        found {}",
+                                       e,
+                                       actual)
+                        })},
+                        Some(expected),
+                        "a structure pattern".to_strbuf(),
+                        None);
                     fcx.write_error(pat.id);
                     kind_name = "[error]";
                     arg_types = subpats.clone()
@@ -217,11 +221,17 @@ pub fn check_pat_variant(pcx: &pat_ctxt, pat: &ast::Pat, path: &ast::Path,
             // See [Note-Type-error-reporting] in middle/typeck/infer/mod.rs
             fcx.infcx().type_error_message_str_with_expected(pat.span,
                                                |expected, actual| {
-                                               expected.map_or("".to_owned(), |e| {
-                    format!("mismatched types: expected `{}` but found {}",
-                         e, actual)})},
-                    Some(expected), "an enum or structure pattern".to_owned(),
-                    None);
+                                               expected.map_or("".to_strbuf(),
+                                                              |e| {
+                        format_strbuf!("mismatched types: expected `{}` but \
+                                        found {}",
+                                       e,
+                                       actual)
+                    })
+                },
+                Some(expected),
+                "an enum or structure pattern".to_strbuf(),
+                None);
             fcx.write_error(pat.id);
             kind_name = "[error]";
             arg_types = subpats.clone()
@@ -446,7 +456,7 @@ pub fn check_pat(pcx: &pat_ctxt, pat: &ast::Pat, expected: ty::t) {
         debug!("pat_range ending type: {:?}", e_ty);
         if !require_same_types(
             tcx, Some(fcx.infcx()), false, pat.span, b_ty, e_ty,
-            || "mismatched types in range".to_owned())
+            || "mismatched types in range".to_strbuf())
         {
             // no-op
         } else if !ty::type_is_numeric(b_ty) && !ty::type_is_char(b_ty) {
@@ -540,11 +550,16 @@ pub fn check_pat(pcx: &pat_ctxt, pat: &ast::Pat, expected: ty::t) {
                // See [Note-Type-error-reporting] in middle/typeck/infer/mod.rs
                 fcx.infcx().type_error_message_str_with_expected(pat.span,
                                                                 |expected, actual| {
-                            expected.map_or("".to_owned(), |e| {
-                                    format!("mismatched types: expected `{}` but found {}",
-                                         e, actual)})},
-                                         Some(expected), "a structure pattern".to_owned(),
-                                         None);
+                            expected.map_or("".to_strbuf(),
+                                            |e| {
+                                format_strbuf!("mismatched types: expected \
+                                                `{}` but found {}",
+                                               e,
+                                               actual)
+                            })},
+                            Some(expected),
+                            "a structure pattern".to_strbuf(),
+                            None);
                 match tcx.def_map.borrow().find(&pat.id) {
                     Some(&ast::DefStruct(supplied_def_id)) => {
                          check_struct_pat(pcx,
@@ -590,17 +605,28 @@ pub fn check_pat(pcx: &pat_ctxt, pat: &ast::Pat, expected: ty::t) {
                 }
                 // use terr_tuple_size if both types are tuples
                 let type_error = match *s {
-                    ty::ty_tup(ref ex_elts) =>
-                        ty::terr_tuple_size(ty::expected_found{expected: ex_elts.len(),
-                                                           found: e_count}),
+                    ty::ty_tup(ref ex_elts) => {
+                        ty::terr_tuple_size(ty::expected_found {
+                            expected: ex_elts.len(),
+                            found: e_count
+                        })
+                    }
                     _ => ty::terr_mismatch
                 };
                 // See [Note-Type-error-reporting] in middle/typeck/infer/mod.rs
-                fcx.infcx().type_error_message_str_with_expected(pat.span, |expected, actual| {
-                        expected.map_or("".to_owned(), |e| {
-                            format!("mismatched types: expected `{}` but found {}",
-                                             e, actual)})},
-                    Some(expected), "tuple".to_owned(), Some(&type_error));
+                fcx.infcx().type_error_message_str_with_expected(pat.span,
+                                                                 |expected,
+                                                                  actual| {
+                        expected.map_or("".to_strbuf(), |e| {
+                            format_strbuf!("mismatched types: expected `{}` \
+                                            but found {}",
+                                           e,
+                                           actual)
+                        }
+                    )},
+                    Some(expected),
+                    "tuple".to_strbuf(),
+                    Some(&type_error));
                 fcx.write_error(pat.id);
             }
         }
@@ -630,11 +656,16 @@ pub fn check_pat(pcx: &pat_ctxt, pat: &ast::Pat, expected: ty::t) {
             fcx.infcx().type_error_message_str_with_expected(
                 pat.span,
                 |expected, actual| {
-                    expected.map_or("".to_owned(), |e| {
-                        format!("mismatched types: expected `{}` but found {}",
-                             e, actual)})},
+                    expected.map_or("".to_strbuf(),
+                                    |e| {
+                        format_strbuf!("mismatched types: expected `{}` but \
+                                        found {}",
+                                       e,
+                                       actual)
+                    })
+                },
                 Some(expected),
-                "a vector pattern".to_owned(),
+                "a vector pattern".to_strbuf(),
                 None);
             fcx.write_error(pat.id);
         };
@@ -648,7 +679,7 @@ pub fn check_pat(pcx: &pat_ctxt, pat: &ast::Pat, expected: ty::t) {
                   fcx.type_error_message(pat.span,
                                          |_| {
                                             "unique vector patterns are no \
-                                             longer supported".to_owned()
+                                             longer supported".to_strbuf()
                                          },
                                          expected,
                                          None);
@@ -716,13 +747,17 @@ pub fn check_pointer_pat(pcx: &pat_ctxt,
             fcx.infcx().type_error_message_str_with_expected(
                 span,
                 |expected, actual| {
-                    expected.map_or("".to_owned(), |e| {
-                        format!("mismatched types: expected `{}` but found {}",
-                             e, actual)})},
+                    expected.map_or("".to_strbuf(), |e| {
+                        format_strbuf!("mismatched types: expected `{}` but \
+                                        found {}",
+                                       e,
+                                       actual)
+                    })
+                },
                 Some(expected),
-                format!("{} pattern", match pointer_kind {
+                format_strbuf!("{} pattern", match pointer_kind {
                     Send => "a box",
-                    Borrowed => "an `&`-pointer"
+                    Borrowed => "an `&`-pointer",
                 }),
                 None);
             fcx.write_error(pat_id);
@@ -731,4 +766,8 @@ pub fn check_pointer_pat(pcx: &pat_ctxt,
 }
 
 #[deriving(Eq)]
-pub enum PointerKind { Send, Borrowed }
+pub enum PointerKind {
+    Send,
+    Borrowed,
+}
+
diff --git a/src/librustc/middle/typeck/check/method.rs b/src/librustc/middle/typeck/check/method.rs
index 17a432d2b5d76..839e3dd080a0a 100644
--- a/src/librustc/middle/typeck/check/method.rs
+++ b/src/librustc/middle/typeck/check/method.rs
@@ -1498,11 +1498,11 @@ impl<'a> LookupContext<'a> {
         self.fcx.tcx()
     }
 
-    fn ty_to_str(&self, t: ty::t) -> ~str {
+    fn ty_to_str(&self, t: ty::t) -> StrBuf {
         self.fcx.infcx().ty_to_str(t)
     }
 
-    fn did_to_str(&self, did: DefId) -> ~str {
+    fn did_to_str(&self, did: DefId) -> StrBuf {
         ty::item_path_str(self.tcx(), did)
     }
 
@@ -1512,23 +1512,24 @@ impl<'a> LookupContext<'a> {
 }
 
 impl Repr for Candidate {
-    fn repr(&self, tcx: &ty::ctxt) -> ~str {
-        format!("Candidate(rcvr_ty={}, rcvr_substs={}, method_ty={}, origin={:?})",
-                self.rcvr_match_condition.repr(tcx),
-                self.rcvr_substs.repr(tcx),
-                self.method_ty.repr(tcx),
-                self.origin)
+    fn repr(&self, tcx: &ty::ctxt) -> StrBuf {
+        format_strbuf!("Candidate(rcvr_ty={}, rcvr_substs={}, method_ty={}, \
+                        origin={:?})",
+                       self.rcvr_match_condition.repr(tcx),
+                       self.rcvr_substs.repr(tcx),
+                       self.method_ty.repr(tcx),
+                       self.origin)
     }
 }
 
 impl Repr for RcvrMatchCondition {
-    fn repr(&self, tcx: &ty::ctxt) -> ~str {
+    fn repr(&self, tcx: &ty::ctxt) -> StrBuf {
         match *self {
             RcvrMatchesIfObject(d) => {
-                format!("RcvrMatchesIfObject({})", d.repr(tcx))
+                format_strbuf!("RcvrMatchesIfObject({})", d.repr(tcx))
             }
             RcvrMatchesIfSubtype(t) => {
-                format!("RcvrMatchesIfSubtype({})", t.repr(tcx))
+                format_strbuf!("RcvrMatchesIfSubtype({})", t.repr(tcx))
             }
         }
     }
diff --git a/src/librustc/middle/typeck/check/mod.rs b/src/librustc/middle/typeck/check/mod.rs
index 472386209e399..94f08b28fed25 100644
--- a/src/librustc/middle/typeck/check/mod.rs
+++ b/src/librustc/middle/typeck/check/mod.rs
@@ -468,7 +468,7 @@ fn check_fn<'a>(ccx: &'a CrateCtxt<'a>,
     let ret_ty = fn_sig.output;
 
     debug!("check_fn(arg_tys={:?}, ret_ty={:?})",
-           arg_tys.iter().map(|&a| ppaux::ty_to_str(tcx, a)).collect::<Vec<~str>>(),
+           arg_tys.iter().map(|&a| ppaux::ty_to_str(tcx, a)).collect::<Vec<StrBuf>>(),
            ppaux::ty_to_str(tcx, ret_ty));
 
     // Create the function context.  This is either derived from scratch or,
@@ -1089,8 +1089,8 @@ impl<'a> RegionScope for infer::InferCtxt<'a> {
 }
 
 impl<'a> FnCtxt<'a> {
-    pub fn tag(&self) -> ~str {
-        format!("{}", self as *FnCtxt)
+    pub fn tag(&self) -> StrBuf {
+        format_strbuf!("{}", self as *FnCtxt)
     }
 
     pub fn local_ty(&self, span: Span, nid: ast::NodeId) -> ty::t {
@@ -1164,7 +1164,7 @@ impl<'a> FnCtxt<'a> {
         ast_ty_to_ty(self, self.infcx(), ast_t)
     }
 
-    pub fn pat_to_str(&self, pat: &ast::Pat) -> ~str {
+    pub fn pat_to_str(&self, pat: &ast::Pat) -> StrBuf {
         pat.repr(self.tcx())
     }
 
@@ -1271,7 +1271,7 @@ impl<'a> FnCtxt<'a> {
 
     pub fn type_error_message(&self,
                               sp: Span,
-                              mk_msg: |~str| -> ~str,
+                              mk_msg: |StrBuf| -> StrBuf,
                               actual_ty: ty::t,
                               err: Option<&ty::type_err>) {
         self.infcx().type_error_message(sp, mk_msg, actual_ty, err);
@@ -1787,7 +1787,7 @@ fn check_expr_with_unifier(fcx: &FnCtxt,
         };
 
         debug!("check_argument_types: formal_tys={:?}",
-               formal_tys.iter().map(|t| fcx.infcx().ty_to_str(*t)).collect::<Vec<~str>>());
+               formal_tys.iter().map(|t| fcx.infcx().ty_to_str(*t)).collect::<Vec<StrBuf>>());
 
         // Check the arguments.
         // We do this in a pretty awful way: first we typecheck any arguments
@@ -1863,18 +1863,24 @@ fn check_expr_with_unifier(fcx: &FnCtxt,
                 match ty::get(arg_ty).sty {
                     ty::ty_float(ast::TyF32) => {
                         fcx.type_error_message(arg.span,
-                                |t| format!("can't pass an {} to variadic function, \
-                                             cast to c_double", t), arg_ty, None);
+                                               |t| {
+                            format_strbuf!("can't pass an {} to variadic \
+                                            function, cast to c_double", t)
+                        }, arg_ty, None);
                     }
                     ty::ty_int(ast::TyI8) | ty::ty_int(ast::TyI16) | ty::ty_bool => {
-                        fcx.type_error_message(arg.span,
-                                |t| format!("can't pass {} to variadic function, cast to c_int",
-                                            t), arg_ty, None);
+                        fcx.type_error_message(arg.span, |t| {
+                            format_strbuf!("can't pass {} to variadic \
+                                            function, cast to c_int",
+                                           t)
+                        }, arg_ty, None);
                     }
                     ty::ty_uint(ast::TyU8) | ty::ty_uint(ast::TyU16) => {
-                        fcx.type_error_message(arg.span,
-                                |t| format!("can't pass {} to variadic function, cast to c_uint",
-                                            t), arg_ty, None);
+                        fcx.type_error_message(arg.span, |t| {
+                            format_strbuf!("can't pass {} to variadic \
+                                            function, cast to c_uint",
+                                           t)
+                        }, arg_ty, None);
                     }
                     _ => {}
                 }
@@ -1920,8 +1926,8 @@ fn check_expr_with_unifier(fcx: &FnCtxt,
             ty::ty_closure(box ty::ClosureTy {sig: ref sig, ..}) => sig,
             _ => {
                 fcx.type_error_message(call_expr.span, |actual| {
-                    format!("expected function but \
-                          found `{}`", actual) }, fn_ty, None);
+                    format_strbuf!("expected function but found `{}`", actual)
+                }, fn_ty, None);
                 &error_fn_sig
             }
         };
@@ -1974,8 +1980,10 @@ fn check_expr_with_unifier(fcx: &FnCtxt,
 
                 fcx.type_error_message(method_name.span,
                   |actual| {
-                      format!("type `{}` does not implement any method in scope named `{}`",
-                              actual, token::get_ident(method_name.node))
+                      format_strbuf!("type `{}` does not implement any \
+                                      method in scope named `{}`",
+                                     actual,
+                                     token::get_ident(method_name.node))
                   },
                   expr_t,
                   None);
@@ -1984,12 +1992,16 @@ fn check_expr_with_unifier(fcx: &FnCtxt,
                 fcx.write_error(expr.id);
 
                 // Check for potential static matches (missing self parameters)
-                method::lookup(fcx, expr, rcvr,
-                                    method_name.node.name,
-                                    expr_t, tps.as_slice(),
-                                    DontDerefArgs,
-                                    CheckTraitsAndInherentMethods,
-                                    DontAutoderefReceiver, ReportStaticMethods);
+                method::lookup(fcx,
+                               expr,
+                               rcvr,
+                               method_name.node.name,
+                               expr_t,
+                               tps.as_slice(),
+                               DontDerefArgs,
+                               CheckTraitsAndInherentMethods,
+                               DontAutoderefReceiver,
+                               ReportStaticMethods);
 
                 ty::mk_err()
             }
@@ -2123,9 +2135,12 @@ fn check_expr_with_unifier(fcx: &FnCtxt,
                         if ty::type_is_fp(ty::simd_type(tcx, lhs_t)) {
                             fcx.type_error_message(expr.span,
                                 |actual| {
-                                    format!("binary comparison operation `{}` not supported \
-                                            for floating point SIMD vector `{}`",
-                                            ast_util::binop_to_str(op), actual)
+                                    format_strbuf!("binary comparison \
+                                                    operation `{}` not \
+                                                    supported for floating \
+                                                    point SIMD vector `{}`",
+                                                   ast_util::binop_to_str(op),
+                                                   actual)
                                 },
                                 lhs_t,
                                 None
@@ -2150,12 +2165,15 @@ fn check_expr_with_unifier(fcx: &FnCtxt,
             // type
             fcx.write_error(expr.id);
             fcx.write_error(rhs.id);
-            fcx.type_error_message(expr.span, |actual| {
-                format!("binary operation `{}` cannot be applied \
-                      to type `{}`",
-                     ast_util::binop_to_str(op), actual)},
-                                   lhs_t, None)
-
+            fcx.type_error_message(expr.span,
+                                   |actual| {
+                    format_strbuf!("binary operation `{}` cannot be applied \
+                                   to type `{}`",
+                                   ast_util::binop_to_str(op),
+                                   actual)
+                },
+                lhs_t,
+                None)
         }
 
         // Check for overloaded operators if not an assignment.
@@ -2164,10 +2182,12 @@ fn check_expr_with_unifier(fcx: &FnCtxt,
         } else {
             fcx.type_error_message(expr.span,
                                    |actual| {
-                                        format!("binary assignment operation \
-                                                `{}=` cannot be applied to type `{}`",
-                                                ast_util::binop_to_str(op),
-                                                actual)
+                                        format_strbuf!("binary assignment \
+                                                        operation `{}=` \
+                                                        cannot be applied to \
+                                                        type `{}`",
+                                                 ast_util::binop_to_str(op),
+                                                 actual)
                                    },
                                    lhs_t,
                                    None);
@@ -2214,8 +2234,10 @@ fn check_expr_with_unifier(fcx: &FnCtxt,
         lookup_op_method(fcx, ex, lhs_resolved_t, token::intern(name),
                          trait_did, [lhs_expr, rhs], DontAutoderefReceiver, || {
             fcx.type_error_message(ex.span, |actual| {
-                format!("binary operation `{}` cannot be applied to type `{}`",
-                    ast_util::binop_to_str(op), actual)
+                format_strbuf!("binary operation `{}` cannot be applied to \
+                                type `{}`",
+                               ast_util::binop_to_str(op),
+                               actual)
             }, lhs_resolved_t, None)
         })
     }
@@ -2230,7 +2252,10 @@ fn check_expr_with_unifier(fcx: &FnCtxt,
        lookup_op_method(fcx, ex, rhs_t, token::intern(mname),
                         trait_did, [rhs_expr], DontAutoderefReceiver, || {
             fcx.type_error_message(ex.span, |actual| {
-                format!("cannot apply unary operator `{}` to type `{}`", op_str, actual)
+                format_strbuf!("cannot apply unary operator `{}` to type \
+                                `{}`",
+                               op_str,
+                               actual)
             }, rhs_t, None);
         })
     }
@@ -2389,8 +2414,10 @@ fn check_expr_with_unifier(fcx: &FnCtxt,
                 fcx.type_error_message(
                     expr.span,
                     |actual| {
-                        format!("attempted to take value of method `{}` on type `{}`",
-                                token::get_name(field), actual)
+                        format_strbuf!("attempted to take value of method \
+                                        `{}` on type `{}`",
+                                       token::get_name(field),
+                                       actual)
                     },
                     expr_t, None);
 
@@ -2402,9 +2429,11 @@ fn check_expr_with_unifier(fcx: &FnCtxt,
                 fcx.type_error_message(
                     expr.span,
                     |actual| {
-                        format!("attempted access of field `{}` on type `{}`, \
-                                 but no field with that name was found",
-                                token::get_name(field), actual)
+                        format_strbuf!("attempted access of field `{}` on \
+                                        type `{}`, but no field with that \
+                                        name was found",
+                                       token::get_name(field),
+                                       actual)
                     },
                     expr_t, None);
             }
@@ -2442,9 +2471,13 @@ fn check_expr_with_unifier(fcx: &FnCtxt,
                     fcx.type_error_message(
                       field.ident.span,
                       |actual| {
-                          format!("structure `{}` has no field named `{}`",
-                                  actual, token::get_ident(field.ident.node))
-                    }, struct_ty, None);
+                          format_strbuf!("structure `{}` has no field named \
+                                          `{}`",
+                                         actual,
+                                         token::get_ident(field.ident.node))
+                      },
+                      struct_ty,
+                      None);
                     error_happened = true;
                 }
                 Some((_, true)) => {
@@ -2701,7 +2734,8 @@ fn check_expr_with_unifier(fcx: &FnCtxt,
                                            .require(GcLangItem) {
                                       Ok(id) => id,
                                       Err(msg) => {
-                                          tcx.sess.span_err(expr.span, msg);
+                                          tcx.sess.span_err(expr.span,
+                                                            msg.as_slice());
                                           ast::DefId {
                                               krate: ast::CRATE_NODE_ID,
                                               node: ast::DUMMY_NODE_ID,
@@ -2825,7 +2859,9 @@ fn check_expr_with_unifier(fcx: &FnCtxt,
                                          no longer be dereferenced");
                                 } else {
                                     fcx.type_error_message(expr.span, |actual| {
-                                        format!("type `{}` cannot be dereferenced", actual)
+                                        format_strbuf!("type `{}` cannot be \
+                                                        dereferenced",
+                                                       actual)
                                     }, oprnd_t, None);
                                 }
                                 ty::mk_err()
@@ -3066,13 +3102,15 @@ fn check_expr_with_unifier(fcx: &FnCtxt,
                 _ => {
                     if ty::type_is_nil(t_e) {
                         fcx.type_error_message(expr.span, |actual| {
-                            format!("cast from nil: `{}` as `{}`", actual,
-                                 fcx.infcx().ty_to_str(t_1))
+                            format_strbuf!("cast from nil: `{}` as `{}`",
+                                           actual,
+                                           fcx.infcx().ty_to_str(t_1))
                         }, t_e, None);
                     } else if ty::type_is_nil(t_1) {
                         fcx.type_error_message(expr.span, |actual| {
-                            format!("cast to nil: `{}` as `{}`", actual,
-                                 fcx.infcx().ty_to_str(t_1))
+                            format_strbuf!("cast to nil: `{}` as `{}`",
+                                           actual,
+                                           fcx.infcx().ty_to_str(t_1))
                         }, t_e, None);
                     }
 
@@ -3092,12 +3130,17 @@ fn check_expr_with_unifier(fcx: &FnCtxt,
                         let te = fcx.infcx().resolve_type_vars_if_possible(te);
                         if ty::get(te).sty != ty::ty_uint(ast::TyU8) {
                             fcx.type_error_message(expr.span, |actual| {
-                                format!("only `u8` can be cast as `char`, not `{}`", actual)
+                                format_strbuf!("only `u8` can be cast as \
+                                                `char`, not `{}`",
+                                               actual)
                             }, t_e, None);
                         }
                     } else if ty::get(t1).sty == ty::ty_bool {
-                        fcx.tcx().sess.span_err(expr.span,
-                                                "cannot cast as `bool`, compare with zero instead");
+                        fcx.tcx()
+                           .sess
+                           .span_err(expr.span,
+                                     "cannot cast as `bool`, compare with \
+                                      zero instead");
                     } else if type_is_region_ptr(fcx, expr.span, t_e) &&
                         type_is_unsafe_ptr(fcx, expr.span, t_1) {
 
@@ -3151,8 +3194,9 @@ fn check_expr_with_unifier(fcx: &FnCtxt,
                         record the issue number in this comment.
                         */
                         fcx.type_error_message(expr.span, |actual| {
-                            format!("non-scalar cast: `{}` as `{}`", actual,
-                                 fcx.infcx().ty_to_str(t_1))
+                            format_strbuf!("non-scalar cast: `{}` as `{}`",
+                                           actual,
+                                           fcx.infcx().ty_to_str(t_1))
                         }, t_e, None);
                     }
                 }
@@ -3271,9 +3315,12 @@ fn check_expr_with_unifier(fcx: &FnCtxt,
                                                     || {
                         fcx.type_error_message(expr.span,
                                                |actual| {
-                                                format!("cannot index a value \
-                                                      of type `{}`",
-                                                     actual)
+                                                    format_strbuf!("cannot \
+                                                                    index a \
+                                                                    value of \
+                                                                    type \
+                                                                    `{}`",
+                                                                    actual)
                                                },
                                                base_t,
                                                None);
@@ -3291,7 +3338,7 @@ fn check_expr_with_unifier(fcx: &FnCtxt,
            ppaux::ty_to_str(tcx, fcx.expr_ty(expr)),
            match expected {
                Some(t) => ppaux::ty_to_str(tcx, t),
-               _ => "empty".to_owned()
+               _ => "empty".to_strbuf()
            });
 
     unifier();
@@ -3300,8 +3347,9 @@ fn check_expr_with_unifier(fcx: &FnCtxt,
 pub fn require_uint(fcx: &FnCtxt, sp: Span, t: ty::t) {
     if !type_is_uint(fcx, sp, t) {
         fcx.type_error_message(sp, |actual| {
-            format!("mismatched types: expected `uint` type but found `{}`",
-                 actual)
+            format_strbuf!("mismatched types: expected `uint` type but found \
+                           `{}`",
+                           actual)
         }, t, None);
     }
 }
@@ -3309,8 +3357,9 @@ pub fn require_uint(fcx: &FnCtxt, sp: Span, t: ty::t) {
 pub fn require_integral(fcx: &FnCtxt, sp: Span, t: ty::t) {
     if !type_is_integral(fcx, sp, t) {
         fcx.type_error_message(sp, |actual| {
-            format!("mismatched types: expected integral type but found `{}`",
-                 actual)
+            format_strbuf!("mismatched types: expected integral type but \
+                            found `{}`",
+                           actual)
         }, t, None);
     }
 }
@@ -3439,8 +3488,13 @@ pub fn check_block_with_expected(fcx: &FnCtxt,
                   ast::StmtExpr(_, _) | ast::StmtSemi(_, _) => true,
                   _ => false
                 } {
-                fcx.ccx.tcx.sess.add_lint(UnreachableCode, s_id, s.span,
-                                          "unreachable statement".to_owned());
+                fcx.ccx
+                   .tcx
+                   .sess
+                   .add_lint(UnreachableCode,
+                             s_id,
+                             s.span,
+                             "unreachable statement".to_strbuf());
                 warned = true;
             }
             if ty::type_is_bot(s_ty) {
@@ -3461,8 +3515,13 @@ pub fn check_block_with_expected(fcx: &FnCtxt,
             },
           Some(e) => {
             if any_bot && !warned {
-                fcx.ccx.tcx.sess.add_lint(UnreachableCode, e.id, e.span,
-                                          "unreachable expression".to_owned());
+                fcx.ccx
+                   .tcx
+                   .sess
+                   .add_lint(UnreachableCode,
+                             e.id,
+                             e.span,
+                             "unreachable expression".to_strbuf());
             }
             check_expr_with_opt_hint(fcx, e, expected);
               let ety = fcx.expr_ty(e);
@@ -3979,7 +4038,8 @@ pub fn structurally_resolved_type(fcx: &FnCtxt, sp: Span, tp: ty::t) -> ty::t {
         Ok(t_s) if !ty::type_is_ty_var(t_s) => t_s,
         _ => {
             fcx.type_error_message(sp, |_actual| {
-                "the type of this value must be known in this context".to_owned()
+                "the type of this value must be known in this \
+                 context".to_strbuf()
             }, tp, None);
             demand::suptype(fcx, sp, ty::mk_err(), tp);
             tp
@@ -4183,7 +4243,7 @@ pub fn check_intrinsic_type(ccx: &CrateCtxt, it: &ast::ForeignItem) {
             "get_tydesc" => {
               let tydesc_ty = match ty::get_tydesc_ty(ccx.tcx) {
                   Ok(t) => t,
-                  Err(s) => { tcx.sess.span_fatal(it.span, s); }
+                  Err(s) => { tcx.sess.span_fatal(it.span, s.as_slice()); }
               };
               let td_ptr = ty::mk_ptr(ccx.tcx, ty::mt {
                   ty: tydesc_ty,
@@ -4199,18 +4259,20 @@ pub fn check_intrinsic_type(ccx: &CrateCtxt, it: &ast::ForeignItem) {
                                                  tps: Vec::new(),
                                                  regions: ty::NonerasedRegions(OwnedSlice::empty())
                                                  }) ),
-                    Err(msg) => { tcx.sess.span_fatal(it.span, msg); }
+                    Err(msg) => {
+                        tcx.sess.span_fatal(it.span, msg.as_slice());
+                    }
                 }
             },
             "visit_tydesc" => {
               let tydesc_ty = match ty::get_tydesc_ty(ccx.tcx) {
                   Ok(t) => t,
-                  Err(s) => { tcx.sess.span_fatal(it.span, s); }
+                  Err(s) => { tcx.sess.span_fatal(it.span, s.as_slice()); }
               };
               let region = ty::ReLateBound(it.id, ty::BrAnon(0));
               let visitor_object_ty = match ty::visitor_object_ty(tcx, region) {
                   Ok((_, vot)) => vot,
-                  Err(s) => { tcx.sess.span_fatal(it.span, s); }
+                  Err(s) => { tcx.sess.span_fatal(it.span, s.as_slice()); }
               };
 
               let td_ptr = ty::mk_ptr(ccx.tcx, ty::mt {
@@ -4387,10 +4449,12 @@ pub fn check_intrinsic_type(ccx: &CrateCtxt, it: &ast::ForeignItem) {
     let fty = ty::mk_bare_fn(tcx, ty::BareFnTy {
         fn_style: ast::UnsafeFn,
         abi: abi::RustIntrinsic,
-        sig: FnSig {binder_id: it.id,
-                    inputs: inputs,
-                    output: output,
-                    variadic: false}
+        sig: FnSig {
+            binder_id: it.id,
+            inputs: inputs,
+            output: output,
+            variadic: false,
+        }
     });
     let i_ty = ty::lookup_item_type(ccx.tcx, local_def(it.id));
     let i_n_tps = i_ty.generics.type_param_defs().len();
@@ -4399,10 +4463,15 @@ pub fn check_intrinsic_type(ccx: &CrateCtxt, it: &ast::ForeignItem) {
                                          of type parameters: found {}, \
                                          expected {}", i_n_tps, n_tps));
     } else {
-        require_same_types(
-            tcx, None, false, it.span, i_ty.ty, fty,
-            || format!("intrinsic has wrong type: \
-                      expected `{}`",
-                     ppaux::ty_to_str(ccx.tcx, fty)));
+        require_same_types(tcx,
+                           None,
+                           false,
+                           it.span,
+                           i_ty.ty,
+                           fty,
+                           || {
+                format_strbuf!("intrinsic has wrong type: expected `{}`",
+                               ppaux::ty_to_str(ccx.tcx, fty))
+            });
     }
 }
diff --git a/src/librustc/middle/typeck/coherence.rs b/src/librustc/middle/typeck/coherence.rs
index c15c30656adcd..f93eb4550a94a 100644
--- a/src/librustc/middle/typeck/coherence.rs
+++ b/src/librustc/middle/typeck/coherence.rs
@@ -421,7 +421,9 @@ impl<'a> CoherenceChecker<'a> {
                             let crate_store = &self.crate_context.tcx.sess.cstore;
                             let cdata = crate_store.get_crate_data(impl_b.krate);
                             session.note(
-                                "conflicting implementation in crate `" + cdata.name + "`");
+                                format!("conflicting implementation in crate \
+                                         `{}`",
+                                        cdata.name));
                         }
                     }
                 }
diff --git a/src/librustc/middle/typeck/collect.rs b/src/librustc/middle/typeck/collect.rs
index baad474844c45..c70204098e0a7 100644
--- a/src/librustc/middle/typeck/collect.rs
+++ b/src/librustc/middle/typeck/collect.rs
@@ -438,8 +438,10 @@ pub fn ensure_supertraits(ccx: &CrateCtxt,
     }
     if sized == ast::StaticSize {
         match tcx.lang_items.require(SizedTraitLangItem) {
-            Ok(def_id) => { ty::try_add_builtin_trait(tcx, def_id, &mut bounds); },
-            Err(s) => tcx.sess.err(s),
+            Ok(def_id) => {
+                ty::try_add_builtin_trait(tcx, def_id, &mut bounds);
+            }
+            Err(s) => tcx.sess.err(s.as_slice()),
         };
     }
 
diff --git a/src/librustc/middle/typeck/infer/combine.rs b/src/librustc/middle/typeck/infer/combine.rs
index b5e15a32b1ca3..84df7230544e6 100644
--- a/src/librustc/middle/typeck/infer/combine.rs
+++ b/src/librustc/middle/typeck/infer/combine.rs
@@ -71,7 +71,7 @@ use syntax::abi;
 
 pub trait Combine {
     fn infcx<'a>(&'a self) -> &'a InferCtxt<'a>;
-    fn tag(&self) -> ~str;
+    fn tag(&self) -> StrBuf;
     fn a_is_expected(&self) -> bool;
     fn trace(&self) -> TypeTrace;
 
diff --git a/src/librustc/middle/typeck/infer/error_reporting.rs b/src/librustc/middle/typeck/infer/error_reporting.rs
index b87b6988a3a60..6f99a0a5ffb2b 100644
--- a/src/librustc/middle/typeck/infer/error_reporting.rs
+++ b/src/librustc/middle/typeck/infer/error_reporting.rs
@@ -103,12 +103,12 @@ pub trait ErrorReporting {
                                      trace: TypeTrace,
                                      terr: &ty::type_err);
 
-    fn values_str(&self, values: &ValuePairs) -> Option<~str>;
+    fn values_str(&self, values: &ValuePairs) -> Option<StrBuf>;
 
     fn expected_found_str<T:UserString+Resolvable>(
         &self,
         exp_found: &ty::expected_found<T>)
-        -> Option<~str>;
+        -> Option<StrBuf>;
 
     fn report_concrete_failure(&self,
                                origin: SubregionOrigin,
@@ -365,7 +365,7 @@ impl<'a> ErrorReporting for InferCtxt<'a> {
         ty::note_and_explain_type_err(self.tcx, terr);
     }
 
-    fn values_str(&self, values: &ValuePairs) -> Option<~str> {
+    fn values_str(&self, values: &ValuePairs) -> Option<StrBuf> {
         /*!
          * Returns a string of the form "expected `{}` but found `{}`",
          * or None if this is a derived error.
@@ -383,7 +383,7 @@ impl<'a> ErrorReporting for InferCtxt<'a> {
     fn expected_found_str<T:UserString+Resolvable>(
         &self,
         exp_found: &ty::expected_found<T>)
-        -> Option<~str>
+        -> Option<StrBuf>
     {
         let expected = exp_found.expected.resolve(self);
         if expected.contains_error() {
@@ -395,9 +395,9 @@ impl<'a> ErrorReporting for InferCtxt<'a> {
             return None;
         }
 
-        Some(format!("expected `{}` but found `{}`",
-                  expected.user_string(self.tcx),
-                  found.user_string(self.tcx)))
+        Some(format_strbuf!("expected `{}` but found `{}`",
+                            expected.user_string(self.tcx),
+                            found.user_string(self.tcx)))
     }
 
     fn report_concrete_failure(&self,
@@ -1449,7 +1449,7 @@ fn lifetimes_in_scope(tcx: &ty::ctxt,
 
 // LifeGiver is responsible for generating fresh lifetime names
 struct LifeGiver {
-    taken: HashSet<~str>,
+    taken: HashSet<StrBuf>,
     counter: Cell<uint>,
     generated: RefCell<Vec<ast::Lifetime>>,
 }
@@ -1458,7 +1458,7 @@ impl LifeGiver {
     fn with_taken(taken: &[ast::Lifetime]) -> LifeGiver {
         let mut taken_ = HashSet::new();
         for lt in taken.iter() {
-            let lt_name = token::get_name(lt.name).get().to_owned();
+            let lt_name = token::get_name(lt.name).get().to_strbuf();
             taken_.insert(lt_name);
         }
         LifeGiver {
@@ -1489,14 +1489,14 @@ impl LifeGiver {
         return lifetime;
 
         // 0 .. 25 generates a .. z, 26 .. 51 generates aa .. zz, and so on
-        fn num_to_str(counter: uint) -> ~str {
+        fn num_to_str(counter: uint) -> StrBuf {
             let mut s = StrBuf::new();
             let (n, r) = (counter/26 + 1, counter % 26);
             let letter: char = from_u32((r+97) as u32).unwrap();
             for _ in range(0, n) {
                 s.push_char(letter);
             }
-            s.into_owned()
+            s
         }
     }
 
diff --git a/src/librustc/middle/typeck/infer/glb.rs b/src/librustc/middle/typeck/infer/glb.rs
index 42b0321e67d58..5ca5945a4f42f 100644
--- a/src/librustc/middle/typeck/infer/glb.rs
+++ b/src/librustc/middle/typeck/infer/glb.rs
@@ -36,7 +36,7 @@ impl<'f> Glb<'f> {
 
 impl<'f> Combine for Glb<'f> {
     fn infcx<'a>(&'a self) -> &'a InferCtxt<'a> { self.get_ref().infcx }
-    fn tag(&self) -> ~str { "glb".to_owned() }
+    fn tag(&self) -> StrBuf { "glb".to_strbuf() }
     fn a_is_expected(&self) -> bool { self.get_ref().a_is_expected }
     fn trace(&self) -> TypeTrace { self.get_ref().trace.clone() }
 
diff --git a/src/librustc/middle/typeck/infer/lub.rs b/src/librustc/middle/typeck/infer/lub.rs
index 804c71da73032..174bdb4a82a3c 100644
--- a/src/librustc/middle/typeck/infer/lub.rs
+++ b/src/librustc/middle/typeck/infer/lub.rs
@@ -35,7 +35,7 @@ impl<'f> Lub<'f> {
 
 impl<'f> Combine for Lub<'f> {
     fn infcx<'a>(&'a self) -> &'a InferCtxt<'a> { self.get_ref().infcx }
-    fn tag(&self) -> ~str { "lub".to_owned() }
+    fn tag(&self) -> StrBuf { "lub".to_strbuf() }
     fn a_is_expected(&self) -> bool { self.get_ref().a_is_expected }
     fn trace(&self) -> TypeTrace { self.get_ref().trace.clone() }
 
diff --git a/src/librustc/middle/typeck/infer/mod.rs b/src/librustc/middle/typeck/infer/mod.rs
index c10ab5205d9b9..53d1092ffd96c 100644
--- a/src/librustc/middle/typeck/infer/mod.rs
+++ b/src/librustc/middle/typeck/infer/mod.rs
@@ -246,15 +246,17 @@ pub enum fixup_err {
     region_var_bound_by_region_var(RegionVid, RegionVid)
 }
 
-pub fn fixup_err_to_str(f: fixup_err) -> ~str {
+pub fn fixup_err_to_str(f: fixup_err) -> StrBuf {
     match f {
-      unresolved_int_ty(_) => "unconstrained integral type".to_owned(),
-      unresolved_ty(_) => "unconstrained type".to_owned(),
-      cyclic_ty(_) => "cyclic type of infinite size".to_owned(),
-      unresolved_region(_) => "unconstrained region".to_owned(),
+      unresolved_int_ty(_) => "unconstrained integral type".to_strbuf(),
+      unresolved_ty(_) => "unconstrained type".to_strbuf(),
+      cyclic_ty(_) => "cyclic type of infinite size".to_strbuf(),
+      unresolved_region(_) => "unconstrained region".to_strbuf(),
       region_var_bound_by_region_var(r1, r2) => {
-        format!("region var {:?} bound by another region var {:?}; this is \
-              a bug in rustc", r1, r2)
+        format_strbuf!("region var {:?} bound by another region var {:?}; \
+                        this is a bug in rustc",
+                       r1,
+                       r2)
       }
     }
 }
@@ -649,17 +651,17 @@ impl<'a> InferCtxt<'a> {
         self.report_region_errors(&errors); // see error_reporting.rs
     }
 
-    pub fn ty_to_str(&self, t: ty::t) -> ~str {
+    pub fn ty_to_str(&self, t: ty::t) -> StrBuf {
         ty_to_str(self.tcx,
                   self.resolve_type_vars_if_possible(t))
     }
 
-    pub fn tys_to_str(&self, ts: &[ty::t]) -> ~str {
-        let tstrs: Vec<~str> = ts.iter().map(|t| self.ty_to_str(*t)).collect();
-        format!("({})", tstrs.connect(", "))
+    pub fn tys_to_str(&self, ts: &[ty::t]) -> StrBuf {
+        let tstrs: Vec<StrBuf> = ts.iter().map(|t| self.ty_to_str(*t)).collect();
+        format_strbuf!("({})", tstrs.connect(", "))
     }
 
-    pub fn trait_ref_to_str(&self, t: &ty::TraitRef) -> ~str {
+    pub fn trait_ref_to_str(&self, t: &ty::TraitRef) -> StrBuf {
         let t = self.resolve_type_vars_in_trait_ref_if_possible(t);
         trait_ref_to_str(self.tcx, &t)
     }
@@ -712,19 +714,19 @@ impl<'a> InferCtxt<'a> {
     // errors.
     pub fn type_error_message_str(&self,
                                   sp: Span,
-                                  mk_msg: |Option<~str>, ~str| -> ~str,
-                                  actual_ty: ~str,
+                                  mk_msg: |Option<StrBuf>, StrBuf| -> StrBuf,
+                                  actual_ty: StrBuf,
                                   err: Option<&ty::type_err>) {
         self.type_error_message_str_with_expected(sp, mk_msg, None, actual_ty, err)
     }
 
     pub fn type_error_message_str_with_expected(&self,
                                                 sp: Span,
-                                                mk_msg: |Option<~str>,
-                                                         ~str|
-                                                         -> ~str,
+                                                mk_msg: |Option<StrBuf>,
+                                                         StrBuf|
+                                                         -> StrBuf,
                                                 expected_ty: Option<ty::t>,
-                                                actual_ty: ~str,
+                                                actual_ty: StrBuf,
                                                 err: Option<&ty::type_err>) {
         debug!("hi! expected_ty = {:?}, actual_ty = {}", expected_ty, actual_ty);
 
@@ -751,7 +753,7 @@ impl<'a> InferCtxt<'a> {
 
     pub fn type_error_message(&self,
                               sp: Span,
-                              mk_msg: |~str| -> ~str,
+                              mk_msg: |StrBuf| -> StrBuf,
                               actual_ty: ty::t,
                               err: Option<&ty::type_err>) {
         let actual_ty = self.resolve_type_vars_if_possible(actual_ty);
@@ -775,10 +777,12 @@ impl<'a> InferCtxt<'a> {
             // Don't report an error if expected is ty_err
             ty::ty_err => return,
             _ => {
-                // if I leave out : ~str, it infers &str and complains
-                |actual: ~str| {
-                    format!("mismatched types: expected `{}` but found `{}`",
-                         self.ty_to_str(resolved_expected), actual)
+                // if I leave out : StrBuf, it infers &str and complains
+                |actual: StrBuf| {
+                    format_strbuf!("mismatched types: expected `{}` but \
+                                    found `{}`",
+                                   self.ty_to_str(resolved_expected),
+                                   actual)
                 }
             }
         };
@@ -818,8 +822,8 @@ impl TypeTrace {
 }
 
 impl Repr for TypeTrace {
-    fn repr(&self, tcx: &ty::ctxt) -> ~str {
-        format!("TypeTrace({})", self.origin.repr(tcx))
+    fn repr(&self, tcx: &ty::ctxt) -> StrBuf {
+        format_strbuf!("TypeTrace({})", self.origin.repr(tcx))
     }
 }
 
@@ -838,15 +842,27 @@ impl TypeOrigin {
 }
 
 impl Repr for TypeOrigin {
-    fn repr(&self, tcx: &ty::ctxt) -> ~str {
+    fn repr(&self, tcx: &ty::ctxt) -> StrBuf {
         match *self {
-            MethodCompatCheck(a) => format!("MethodCompatCheck({})", a.repr(tcx)),
-            ExprAssignable(a) => format!("ExprAssignable({})", a.repr(tcx)),
-            Misc(a) => format!("Misc({})", a.repr(tcx)),
-            RelateTraitRefs(a) => format!("RelateTraitRefs({})", a.repr(tcx)),
-            RelateSelfType(a) => format!("RelateSelfType({})", a.repr(tcx)),
-            MatchExpression(a) => format!("MatchExpression({})", a.repr(tcx)),
-            IfExpression(a) => format!("IfExpression({})", a.repr(tcx)),
+            MethodCompatCheck(a) => {
+                format_strbuf!("MethodCompatCheck({})", a.repr(tcx))
+            }
+            ExprAssignable(a) => {
+                format_strbuf!("ExprAssignable({})", a.repr(tcx))
+            }
+            Misc(a) => format_strbuf!("Misc({})", a.repr(tcx)),
+            RelateTraitRefs(a) => {
+                format_strbuf!("RelateTraitRefs({})", a.repr(tcx))
+            }
+            RelateSelfType(a) => {
+                format_strbuf!("RelateSelfType({})", a.repr(tcx))
+            }
+            MatchExpression(a) => {
+                format_strbuf!("MatchExpression({})", a.repr(tcx))
+            }
+            IfExpression(a) => {
+                format_strbuf!("IfExpression({})", a.repr(tcx))
+            }
         }
     }
 }
@@ -875,26 +891,44 @@ impl SubregionOrigin {
 }
 
 impl Repr for SubregionOrigin {
-    fn repr(&self, tcx: &ty::ctxt) -> ~str {
+    fn repr(&self, tcx: &ty::ctxt) -> StrBuf {
         match *self {
-            Subtype(ref a) => format!("Subtype({})", a.repr(tcx)),
-            InfStackClosure(a) => format!("InfStackClosure({})", a.repr(tcx)),
-            InvokeClosure(a) => format!("InvokeClosure({})", a.repr(tcx)),
-            DerefPointer(a) => format!("DerefPointer({})", a.repr(tcx)),
-            FreeVariable(a, b) => format!("FreeVariable({}, {})", a.repr(tcx), b),
-            IndexSlice(a) => format!("IndexSlice({})", a.repr(tcx)),
-            RelateObjectBound(a) => format!("RelateObjectBound({})", a.repr(tcx)),
-            Reborrow(a) => format!("Reborrow({})", a.repr(tcx)),
-            ReborrowUpvar(a, b) => format!("ReborrowUpvar({},{:?})", a.repr(tcx), b),
-            ReferenceOutlivesReferent(_, a) =>
-                format!("ReferenceOutlivesReferent({})", a.repr(tcx)),
-            BindingTypeIsNotValidAtDecl(a) =>
-                format!("BindingTypeIsNotValidAtDecl({})", a.repr(tcx)),
-            CallRcvr(a) => format!("CallRcvr({})", a.repr(tcx)),
-            CallArg(a) => format!("CallArg({})", a.repr(tcx)),
-            CallReturn(a) => format!("CallReturn({})", a.repr(tcx)),
-            AddrOf(a) => format!("AddrOf({})", a.repr(tcx)),
-            AutoBorrow(a) => format!("AutoBorrow({})", a.repr(tcx)),
+            Subtype(ref a) => {
+                format_strbuf!("Subtype({})", a.repr(tcx))
+            }
+            InfStackClosure(a) => {
+                format_strbuf!("InfStackClosure({})", a.repr(tcx))
+            }
+            InvokeClosure(a) => {
+                format_strbuf!("InvokeClosure({})", a.repr(tcx))
+            }
+            DerefPointer(a) => {
+                format_strbuf!("DerefPointer({})", a.repr(tcx))
+            }
+            FreeVariable(a, b) => {
+                format_strbuf!("FreeVariable({}, {})", a.repr(tcx), b)
+            }
+            IndexSlice(a) => {
+                format_strbuf!("IndexSlice({})", a.repr(tcx))
+            }
+            RelateObjectBound(a) => {
+                format_strbuf!("RelateObjectBound({})", a.repr(tcx))
+            }
+            Reborrow(a) => format_strbuf!("Reborrow({})", a.repr(tcx)),
+            ReborrowUpvar(a, b) => {
+                format_strbuf!("ReborrowUpvar({},{:?})", a.repr(tcx), b)
+            }
+            ReferenceOutlivesReferent(_, a) => {
+                format_strbuf!("ReferenceOutlivesReferent({})", a.repr(tcx))
+            }
+            BindingTypeIsNotValidAtDecl(a) => {
+                format_strbuf!("BindingTypeIsNotValidAtDecl({})", a.repr(tcx))
+            }
+            CallRcvr(a) => format_strbuf!("CallRcvr({})", a.repr(tcx)),
+            CallArg(a) => format_strbuf!("CallArg({})", a.repr(tcx)),
+            CallReturn(a) => format_strbuf!("CallReturn({})", a.repr(tcx)),
+            AddrOf(a) => format_strbuf!("AddrOf({})", a.repr(tcx)),
+            AutoBorrow(a) => format_strbuf!("AutoBorrow({})", a.repr(tcx)),
         }
     }
 }
@@ -918,25 +952,43 @@ impl RegionVariableOrigin {
 }
 
 impl Repr for RegionVariableOrigin {
-    fn repr(&self, tcx: &ty::ctxt) -> ~str {
+    fn repr(&self, tcx: &ty::ctxt) -> StrBuf {
         match *self {
-            MiscVariable(a) => format!("MiscVariable({})", a.repr(tcx)),
-            PatternRegion(a) => format!("PatternRegion({})", a.repr(tcx)),
-            AddrOfRegion(a) => format!("AddrOfRegion({})", a.repr(tcx)),
-            AddrOfSlice(a) => format!("AddrOfSlice({})", a.repr(tcx)),
-            Autoref(a) => format!("Autoref({})", a.repr(tcx)),
-            Coercion(ref a) => format!("Coercion({})", a.repr(tcx)),
-            EarlyBoundRegion(a, b) => format!("EarlyBoundRegion({},{})",
-                                              a.repr(tcx), b.repr(tcx)),
-            LateBoundRegion(a, b) => format!("LateBoundRegion({},{})",
-                                             a.repr(tcx), b.repr(tcx)),
-            BoundRegionInFnType(a, b) => format!("bound_regionInFnType({},{})",
-                                              a.repr(tcx), b.repr(tcx)),
-            BoundRegionInCoherence(a) => format!("bound_regionInCoherence({})",
-                                                 a.repr(tcx)),
-            UpvarRegion(a, b) => format!("UpvarRegion({}, {})",
-                                         a.repr(tcx),
-                                         b.repr(tcx)),
+            MiscVariable(a) => {
+                format_strbuf!("MiscVariable({})", a.repr(tcx))
+            }
+            PatternRegion(a) => {
+                format_strbuf!("PatternRegion({})", a.repr(tcx))
+            }
+            AddrOfRegion(a) => {
+                format_strbuf!("AddrOfRegion({})", a.repr(tcx))
+            }
+            AddrOfSlice(a) => format_strbuf!("AddrOfSlice({})", a.repr(tcx)),
+            Autoref(a) => format_strbuf!("Autoref({})", a.repr(tcx)),
+            Coercion(ref a) => format_strbuf!("Coercion({})", a.repr(tcx)),
+            EarlyBoundRegion(a, b) => {
+                format_strbuf!("EarlyBoundRegion({},{})",
+                               a.repr(tcx),
+                               b.repr(tcx))
+            }
+            LateBoundRegion(a, b) => {
+                format_strbuf!("LateBoundRegion({},{})",
+                               a.repr(tcx),
+                               b.repr(tcx))
+            }
+            BoundRegionInFnType(a, b) => {
+                format_strbuf!("bound_regionInFnType({},{})",
+                               a.repr(tcx),
+                               b.repr(tcx))
+            }
+            BoundRegionInCoherence(a) => {
+                format_strbuf!("bound_regionInCoherence({})", a.repr(tcx))
+            }
+            UpvarRegion(a, b) => {
+                format_strbuf!("UpvarRegion({}, {})",
+                               a.repr(tcx),
+                               b.repr(tcx))
+            }
         }
     }
 }
diff --git a/src/librustc/middle/typeck/infer/region_inference/mod.rs b/src/librustc/middle/typeck/infer/region_inference/mod.rs
index bb6d479870b91..297a29211478b 100644
--- a/src/librustc/middle/typeck/infer/region_inference/mod.rs
+++ b/src/librustc/middle/typeck/infer/region_inference/mod.rs
@@ -1332,16 +1332,28 @@ impl<'a> RegionVarBindings<'a> {
 }
 
 impl Repr for Constraint {
-    fn repr(&self, tcx: &ty::ctxt) -> ~str {
+    fn repr(&self, tcx: &ty::ctxt) -> StrBuf {
         match *self {
-            ConstrainVarSubVar(a, b) => format!("ConstrainVarSubVar({}, {})",
-                                             a.repr(tcx), b.repr(tcx)),
-            ConstrainRegSubVar(a, b) => format!("ConstrainRegSubVar({}, {})",
-                                             a.repr(tcx), b.repr(tcx)),
-            ConstrainVarSubReg(a, b) => format!("ConstrainVarSubReg({}, {})",
-                                             a.repr(tcx), b.repr(tcx)),
-            ConstrainRegSubReg(a, b) => format!("ConstrainRegSubReg({}, {})",
-                                             a.repr(tcx), b.repr(tcx)),
+            ConstrainVarSubVar(a, b) => {
+                format_strbuf!("ConstrainVarSubVar({}, {})",
+                               a.repr(tcx),
+                               b.repr(tcx))
+            }
+            ConstrainRegSubVar(a, b) => {
+                format_strbuf!("ConstrainRegSubVar({}, {})",
+                               a.repr(tcx),
+                               b.repr(tcx))
+            }
+            ConstrainVarSubReg(a, b) => {
+                format_strbuf!("ConstrainVarSubReg({}, {})",
+                               a.repr(tcx),
+                               b.repr(tcx))
+            }
+            ConstrainRegSubReg(a, b) => {
+                format_strbuf!("ConstrainRegSubReg({}, {})",
+                               a.repr(tcx),
+                               b.repr(tcx))
+            }
         }
     }
 }
diff --git a/src/librustc/middle/typeck/infer/sub.rs b/src/librustc/middle/typeck/infer/sub.rs
index 2c8acd0573b74..437a43ed74cff 100644
--- a/src/librustc/middle/typeck/infer/sub.rs
+++ b/src/librustc/middle/typeck/infer/sub.rs
@@ -35,7 +35,7 @@ impl<'f> Sub<'f> {
 
 impl<'f> Combine for Sub<'f> {
     fn infcx<'a>(&'a self) -> &'a InferCtxt<'a> { self.get_ref().infcx }
-    fn tag(&self) -> ~str { "sub".to_owned() }
+    fn tag(&self) -> StrBuf { "sub".to_strbuf() }
     fn a_is_expected(&self) -> bool { self.get_ref().a_is_expected }
     fn trace(&self) -> TypeTrace { self.get_ref().trace.clone() }
 
diff --git a/src/librustc/middle/typeck/infer/test.rs b/src/librustc/middle/typeck/infer/test.rs
index a8ff7d4ee7f6e..3b2c721448655 100644
--- a/src/librustc/middle/typeck/infer/test.rs
+++ b/src/librustc/middle/typeck/infer/test.rs
@@ -34,7 +34,7 @@ struct Env {
     krate: @ast::Crate,
     tcx: ty::ctxt,
     infcx: infer::infer_ctxt,
-    err_messages: @DVec<~str>
+    err_messages: @DVec<StrBuf>
 }
 
 struct RH {
@@ -93,7 +93,7 @@ impl Env {
                             sub: &[]}]});
     }
 
-    pub fn lookup_item(&self, names: &[~str]) -> ast::node_id {
+    pub fn lookup_item(&self, names: &[StrBuf]) -> ast::node_id {
         return match search_mod(self, &self.krate.node.module, 0, names) {
             Some(id) => id,
             None => {
@@ -104,7 +104,7 @@ impl Env {
         fn search_mod(self: &Env,
                       m: &ast::Mod,
                       idx: uint,
-                      names: &[~str]) -> Option<ast::node_id> {
+                      names: &[StrBuf]) -> Option<ast::node_id> {
             assert!(idx < names.len());
             for item in m.items.iter() {
                 if self.tcx.sess.str_of(item.ident) == names[idx] {
@@ -117,7 +117,7 @@ impl Env {
         fn search(self: &Env,
                   it: @ast::Item,
                   idx: uint,
-                  names: &[~str]) -> Option<ast::node_id> {
+                  names: &[StrBuf]) -> Option<ast::node_id> {
             if idx == names.len() {
                 return Some(it.id);
             }
@@ -174,7 +174,7 @@ impl Env {
         self.assert_subtype(b, a);
     }
 
-    pub fn ty_to_str(&self, a: ty::t) -> ~str {
+    pub fn ty_to_str(&self, a: ty::t) -> StrBuf {
         ty_to_str(self.tcx, a)
     }
 
diff --git a/src/librustc/middle/typeck/infer/to_str.rs b/src/librustc/middle/typeck/infer/to_str.rs
index fd3c9faa33e6f..30857f4c38311 100644
--- a/src/librustc/middle/typeck/infer/to_str.rs
+++ b/src/librustc/middle/typeck/infer/to_str.rs
@@ -20,75 +20,80 @@ use util::ppaux::{mt_to_str, ty_to_str, trait_ref_to_str};
 use syntax::ast;
 
 pub trait InferStr {
-    fn inf_str(&self, cx: &InferCtxt) -> ~str;
+    fn inf_str(&self, cx: &InferCtxt) -> StrBuf;
 }
 
 impl InferStr for ty::t {
-    fn inf_str(&self, cx: &InferCtxt) -> ~str {
+    fn inf_str(&self, cx: &InferCtxt) -> StrBuf {
         ty_to_str(cx.tcx, *self)
     }
 }
 
 impl InferStr for FnSig {
-    fn inf_str(&self, cx: &InferCtxt) -> ~str {
-        format!("({}) -> {}",
-             self.inputs.iter().map(|a| a.inf_str(cx)).collect::<Vec<~str>>().connect(", "),
-             self.output.inf_str(cx))
+    fn inf_str(&self, cx: &InferCtxt) -> StrBuf {
+        format_strbuf!("({}) -> {}",
+                       self.inputs
+                           .iter()
+                           .map(|a| a.inf_str(cx))
+                           .collect::<Vec<StrBuf>>().connect(", "),
+                       self.output.inf_str(cx))
     }
 }
 
 impl InferStr for ty::mt {
-    fn inf_str(&self, cx: &InferCtxt) -> ~str {
+    fn inf_str(&self, cx: &InferCtxt) -> StrBuf {
         mt_to_str(cx.tcx, self)
     }
 }
 
 impl InferStr for ty::Region {
-    fn inf_str(&self, _cx: &InferCtxt) -> ~str {
-        format!("{:?}", *self)
+    fn inf_str(&self, _cx: &InferCtxt) -> StrBuf {
+        format_strbuf!("{:?}", *self)
     }
 }
 
 impl<V:InferStr> InferStr for Bound<V> {
-    fn inf_str(&self, cx: &InferCtxt) -> ~str {
+    fn inf_str(&self, cx: &InferCtxt) -> StrBuf {
         match *self {
-          Some(ref v) => v.inf_str(cx),
-          None => "none".to_owned()
+            Some(ref v) => v.inf_str(cx),
+            None => "none".to_strbuf()
         }
     }
 }
 
 impl<T:InferStr> InferStr for Bounds<T> {
-    fn inf_str(&self, cx: &InferCtxt) -> ~str {
-        format!("\\{{} <: {}\\}",
-             self.lb.inf_str(cx),
-             self.ub.inf_str(cx))
+    fn inf_str(&self, cx: &InferCtxt) -> StrBuf {
+        format_strbuf!("\\{{} <: {}\\}",
+                       self.lb.inf_str(cx),
+                       self.ub.inf_str(cx))
     }
 }
 
 impl<V:Vid + ToStr,T:InferStr> InferStr for VarValue<V, T> {
-    fn inf_str(&self, cx: &InferCtxt) -> ~str {
+    fn inf_str(&self, cx: &InferCtxt) -> StrBuf {
         match *self {
-          Redirect(ref vid) => format!("Redirect({})", vid.to_str()),
-          Root(ref pt, rk) => format!("Root({}, {})", pt.inf_str(cx), rk)
+          Redirect(ref vid) => format_strbuf!("Redirect({})", vid.to_str()),
+          Root(ref pt, rk) => {
+              format_strbuf!("Root({}, {})", pt.inf_str(cx), rk)
+          }
         }
     }
 }
 
 impl InferStr for IntVarValue {
-    fn inf_str(&self, _cx: &InferCtxt) -> ~str {
-        self.to_str()
+    fn inf_str(&self, _cx: &InferCtxt) -> StrBuf {
+        self.to_str().to_strbuf()
     }
 }
 
 impl InferStr for ast::FloatTy {
-    fn inf_str(&self, _cx: &InferCtxt) -> ~str {
-        self.to_str()
+    fn inf_str(&self, _cx: &InferCtxt) -> StrBuf {
+        self.to_str().to_strbuf()
     }
 }
 
 impl InferStr for ty::TraitRef {
-    fn inf_str(&self, cx: &InferCtxt) -> ~str {
+    fn inf_str(&self, cx: &InferCtxt) -> StrBuf {
         trait_ref_to_str(cx.tcx, self)
     }
 }
diff --git a/src/librustc/middle/typeck/mod.rs b/src/librustc/middle/typeck/mod.rs
index 83300f6dba705..165c573d056ed 100644
--- a/src/librustc/middle/typeck/mod.rs
+++ b/src/librustc/middle/typeck/mod.rs
@@ -198,18 +198,18 @@ pub enum vtable_origin {
 }
 
 impl Repr for vtable_origin {
-    fn repr(&self, tcx: &ty::ctxt) -> ~str {
+    fn repr(&self, tcx: &ty::ctxt) -> StrBuf {
         match *self {
             vtable_static(def_id, ref tys, ref vtable_res) => {
-                format!("vtable_static({:?}:{}, {}, {})",
-                     def_id,
-                     ty::item_path_str(tcx, def_id),
-                     tys.repr(tcx),
-                     vtable_res.repr(tcx))
+                format_strbuf!("vtable_static({:?}:{}, {}, {})",
+                               def_id,
+                               ty::item_path_str(tcx, def_id),
+                               tys.repr(tcx),
+                               vtable_res.repr(tcx))
             }
 
             vtable_param(x, y) => {
-                format!("vtable_param({:?}, {:?})", x, y)
+                format_strbuf!("vtable_param({:?}, {:?})", x, y)
             }
         }
     }
@@ -230,10 +230,10 @@ pub struct impl_res {
 }
 
 impl Repr for impl_res {
-    fn repr(&self, tcx: &ty::ctxt) -> ~str {
-        format!("impl_res \\{trait_vtables={}, self_vtables={}\\}",
-             self.trait_vtables.repr(tcx),
-             self.self_vtables.repr(tcx))
+    fn repr(&self, tcx: &ty::ctxt) -> StrBuf {
+        format_strbuf!("impl_res \\{trait_vtables={}, self_vtables={}\\}",
+                       self.trait_vtables.repr(tcx),
+                       self.self_vtables.repr(tcx))
     }
 }
 
@@ -293,7 +293,7 @@ pub fn require_same_types(tcx: &ty::ctxt,
                           span: Span,
                           t1: ty::t,
                           t2: ty::t,
-                          msg: || -> ~str)
+                          msg: || -> StrBuf)
                           -> bool {
     let result = match maybe_infcx {
         None => {
@@ -308,8 +308,10 @@ pub fn require_same_types(tcx: &ty::ctxt,
     match result {
         Ok(_) => true,
         Err(ref terr) => {
-            tcx.sess.span_err(span, msg() + ": " +
-                              ty::type_err_to_str(tcx, terr));
+            tcx.sess.span_err(span,
+                              format!("{}: {}",
+                                      msg(),
+                                      ty::type_err_to_str(tcx, terr)));
             ty::note_and_explain_type_err(tcx, terr);
             false
         }
@@ -350,8 +352,10 @@ fn check_main_fn_ty(ccx: &CrateCtxt,
             });
 
             require_same_types(tcx, None, false, main_span, main_t, se_ty,
-                || format!("main function expects type: `{}`",
-                        ppaux::ty_to_str(ccx.tcx, se_ty)));
+                || {
+                    format_strbuf!("main function expects type: `{}`",
+                                   ppaux::ty_to_str(ccx.tcx, se_ty))
+                });
         }
         _ => {
             tcx.sess.span_bug(main_span,
@@ -399,7 +403,10 @@ fn check_start_fn_ty(ccx: &CrateCtxt,
             });
 
             require_same_types(tcx, None, false, start_span, start_t, se_ty,
-                || format!("start function expects type: `{}`", ppaux::ty_to_str(ccx.tcx, se_ty)));
+                || {
+                    format_strbuf!("start function expects type: `{}`",
+                                   ppaux::ty_to_str(ccx.tcx, se_ty))
+                });
 
         }
         _ => {
diff --git a/src/librustc/middle/typeck/variance.rs b/src/librustc/middle/typeck/variance.rs
index df3af87b0f824..f2f86485b1997 100644
--- a/src/librustc/middle/typeck/variance.rs
+++ b/src/librustc/middle/typeck/variance.rs
@@ -1001,7 +1001,7 @@ impl<'a> SolveContext<'a> {
             // attribute and report an error with various results if found.
             if ty::has_attr(tcx, item_def_id, "rustc_variance") {
                 let found = item_variances.repr(tcx);
-                tcx.sess.span_err(tcx.map.span(item_id), found);
+                tcx.sess.span_err(tcx.map.span(item_id), found.as_slice());
             }
 
             let newly_added = tcx.item_variance_map.borrow_mut()
diff --git a/src/librustc/util/ppaux.rs b/src/librustc/util/ppaux.rs
index b81746c11d524..5060c5572cdbb 100644
--- a/src/librustc/util/ppaux.rs
+++ b/src/librustc/util/ppaux.rs
@@ -34,12 +34,12 @@ use syntax::owned_slice::OwnedSlice;
 
 /// Produces a string suitable for debugging output.
 pub trait Repr {
-    fn repr(&self, tcx: &ctxt) -> ~str;
+    fn repr(&self, tcx: &ctxt) -> StrBuf;
 }
 
 /// Produces a string suitable for showing to the user.
 pub trait UserString {
-    fn user_string(&self, tcx: &ctxt) -> ~str;
+    fn user_string(&self, tcx: &ctxt) -> StrBuf;
 }
 
 pub fn note_and_explain_region(cx: &ctxt,
@@ -60,7 +60,7 @@ pub fn note_and_explain_region(cx: &ctxt,
 }
 
 pub fn explain_region_and_span(cx: &ctxt, region: ty::Region)
-                            -> (~str, Option<Span>) {
+                            -> (StrBuf, Option<Span>) {
     return match region {
       ReScope(node_id) => {
         match cx.map.find(node_id) {
@@ -86,7 +86,8 @@ pub fn explain_region_and_span(cx: &ctxt, region: ty::Region)
           }
           Some(_) | None => {
             // this really should not happen
-            (format!("unknown scope: {}.  Please report a bug.", node_id),
+            (format_strbuf!("unknown scope: {}.  Please report a bug.",
+                            node_id),
              None)
           }
         }
@@ -94,82 +95,92 @@ pub fn explain_region_and_span(cx: &ctxt, region: ty::Region)
 
       ReFree(ref fr) => {
         let prefix = match fr.bound_region {
-          BrAnon(idx) => format!("the anonymous lifetime \\#{} defined on",
-                               idx + 1),
-          BrFresh(_) => format!("an anonymous lifetime defined on"),
-          _ => format!("the lifetime {} as defined on",
-                    bound_region_ptr_to_str(cx, fr.bound_region))
+          BrAnon(idx) => {
+              format_strbuf!("the anonymous lifetime \\#{} defined on",
+                             idx + 1)
+          }
+          BrFresh(_) => "an anonymous lifetime defined on".to_strbuf(),
+          _ => {
+              format_strbuf!("the lifetime {} as defined on",
+                             bound_region_ptr_to_str(cx, fr.bound_region))
+          }
         };
 
         match cx.map.find(fr.scope_id) {
           Some(ast_map::NodeBlock(ref blk)) => {
             let (msg, opt_span) = explain_span(cx, "block", blk.span);
-            (format!("{} {}", prefix, msg), opt_span)
+            (format_strbuf!("{} {}", prefix, msg), opt_span)
           }
           Some(ast_map::NodeItem(it)) if match it.node {
                 ast::ItemImpl(..) => true, _ => false} => {
             let (msg, opt_span) = explain_span(cx, "impl", it.span);
-            (format!("{} {}", prefix, msg), opt_span)
+            (format_strbuf!("{} {}", prefix, msg), opt_span)
           }
           Some(_) | None => {
             // this really should not happen
-            (format!("{} node {}", prefix, fr.scope_id), None)
+            (format_strbuf!("{} node {}", prefix, fr.scope_id), None)
           }
         }
       }
 
-      ReStatic => { ("the static lifetime".to_owned(), None) }
+      ReStatic => { ("the static lifetime".to_strbuf(), None) }
 
-      ReEmpty => { ("the empty lifetime".to_owned(), None) }
+      ReEmpty => { ("the empty lifetime".to_strbuf(), None) }
 
       // I believe these cases should not occur (except when debugging,
       // perhaps)
       ty::ReInfer(_) | ty::ReEarlyBound(..) | ty::ReLateBound(..) => {
-        (format!("lifetime {:?}", region), None)
+        (format_strbuf!("lifetime {:?}", region), None)
       }
     };
 
     fn explain_span(cx: &ctxt, heading: &str, span: Span)
-        -> (~str, Option<Span>) {
+        -> (StrBuf, Option<Span>) {
         let lo = cx.sess.codemap().lookup_char_pos_adj(span.lo);
-        (format!("the {} at {}:{}", heading,
-              lo.line, lo.col.to_uint()), Some(span))
+        (format_strbuf!("the {} at {}:{}",
+                        heading,
+                        lo.line,
+                        lo.col.to_uint()), Some(span))
     }
 }
 
-pub fn bound_region_ptr_to_str(cx: &ctxt, br: BoundRegion) -> ~str {
+pub fn bound_region_ptr_to_str(cx: &ctxt, br: BoundRegion) -> StrBuf {
     bound_region_to_str(cx, "&", true, br)
 }
 
 pub fn bound_region_to_str(cx: &ctxt,
                            prefix: &str, space: bool,
-                           br: BoundRegion) -> ~str {
+                           br: BoundRegion) -> StrBuf {
     let space_str = if space { " " } else { "" };
 
     if cx.sess.verbose() {
-        return format!("{}{}{}", prefix, br.repr(cx), space_str);
+        return format_strbuf!("{}{}{}", prefix, br.repr(cx), space_str)
     }
 
     match br {
-        BrNamed(_, name)   => format!("{}'{}{}", prefix,
-                                      token::get_name(name), space_str),
-        BrAnon(_)           => prefix.to_str(),
-        BrFresh(_)          => prefix.to_str(),
+        BrNamed(_, name) => {
+            format_strbuf!("{}'{}{}",
+                           prefix,
+                           token::get_name(name),
+                           space_str)
+        }
+        BrAnon(_) => prefix.to_strbuf(),
+        BrFresh(_) => prefix.to_strbuf(),
     }
 }
 
 // In general, if you are giving a region error message,
 // you should use `explain_region()` or, better yet,
 // `note_and_explain_region()`
-pub fn region_ptr_to_str(cx: &ctxt, region: Region) -> ~str {
+pub fn region_ptr_to_str(cx: &ctxt, region: Region) -> StrBuf {
     region_to_str(cx, "&", true, region)
 }
 
-pub fn region_to_str(cx: &ctxt, prefix: &str, space: bool, region: Region) -> ~str {
+pub fn region_to_str(cx: &ctxt, prefix: &str, space: bool, region: Region) -> StrBuf {
     let space_str = if space { " " } else { "" };
 
     if cx.sess.verbose() {
-        return format!("{}{}{}", prefix, region.repr(cx), space_str);
+        return format_strbuf!("{}{}{}", prefix, region.repr(cx), space_str)
     }
 
     // These printouts are concise.  They do not contain all the information
@@ -177,65 +188,69 @@ pub fn region_to_str(cx: &ctxt, prefix: &str, space: bool, region: Region) -> ~s
     // to fit that into a short string.  Hence the recommendation to use
     // `explain_region()` or `note_and_explain_region()`.
     match region {
-        ty::ReScope(_) => prefix.to_str(),
-        ty::ReEarlyBound(_, _, name) => token::get_name(name).get().to_str(),
+        ty::ReScope(_) => prefix.to_strbuf(),
+        ty::ReEarlyBound(_, _, name) => {
+            token::get_name(name).get().to_strbuf()
+        }
         ty::ReLateBound(_, br) => bound_region_to_str(cx, prefix, space, br),
         ty::ReFree(ref fr) => bound_region_to_str(cx, prefix, space, fr.bound_region),
         ty::ReInfer(ReSkolemized(_, br)) => {
             bound_region_to_str(cx, prefix, space, br)
         }
-        ty::ReInfer(ReVar(_)) => prefix.to_str(),
-        ty::ReStatic => format!("{}'static{}", prefix, space_str),
-        ty::ReEmpty => format!("{}'<empty>{}", prefix, space_str)
+        ty::ReInfer(ReVar(_)) => prefix.to_strbuf(),
+        ty::ReStatic => format_strbuf!("{}'static{}", prefix, space_str),
+        ty::ReEmpty => format_strbuf!("{}'<empty>{}", prefix, space_str),
     }
 }
 
-pub fn mutability_to_str(m: ast::Mutability) -> ~str {
+pub fn mutability_to_str(m: ast::Mutability) -> StrBuf {
     match m {
-        ast::MutMutable => "mut ".to_owned(),
-        ast::MutImmutable => "".to_owned(),
+        ast::MutMutable => "mut ".to_strbuf(),
+        ast::MutImmutable => "".to_strbuf(),
     }
 }
 
-pub fn mt_to_str(cx: &ctxt, m: &mt) -> ~str {
-    format!("{}{}", mutability_to_str(m.mutbl), ty_to_str(cx, m.ty))
+pub fn mt_to_str(cx: &ctxt, m: &mt) -> StrBuf {
+    format_strbuf!("{}{}", mutability_to_str(m.mutbl), ty_to_str(cx, m.ty))
 }
 
-pub fn trait_store_to_str(cx: &ctxt, s: ty::TraitStore) -> ~str {
+pub fn trait_store_to_str(cx: &ctxt, s: ty::TraitStore) -> StrBuf {
     match s {
-        ty::UniqTraitStore => "Box ".to_owned(),
+        ty::UniqTraitStore => "Box ".to_strbuf(),
         ty::RegionTraitStore(r, m) => {
-            format!("{}{}", region_ptr_to_str(cx, r), mutability_to_str(m))
+            format_strbuf!("{}{}",
+                           region_ptr_to_str(cx, r),
+                           mutability_to_str(m))
         }
     }
 }
 
-pub fn vec_map_to_str<T>(ts: &[T], f: |t: &T| -> ~str) -> ~str {
-    let tstrs = ts.iter().map(f).collect::<Vec<~str>>();
-    format!("[{}]", tstrs.connect(", "))
+pub fn vec_map_to_str<T>(ts: &[T], f: |t: &T| -> StrBuf) -> StrBuf {
+    let tstrs = ts.iter().map(f).collect::<Vec<StrBuf>>();
+    format_strbuf!("[{}]", tstrs.connect(", "))
 }
 
-pub fn fn_sig_to_str(cx: &ctxt, typ: &ty::FnSig) -> ~str {
-    format!("fn{}{} -> {}",
-            typ.binder_id,
-            typ.inputs.repr(cx),
-            typ.output.repr(cx))
+pub fn fn_sig_to_str(cx: &ctxt, typ: &ty::FnSig) -> StrBuf {
+    format_strbuf!("fn{}{} -> {}",
+                   typ.binder_id,
+                   typ.inputs.repr(cx),
+                   typ.output.repr(cx))
 }
 
-pub fn trait_ref_to_str(cx: &ctxt, trait_ref: &ty::TraitRef) -> ~str {
-    trait_ref.user_string(cx)
+pub fn trait_ref_to_str(cx: &ctxt, trait_ref: &ty::TraitRef) -> StrBuf {
+    trait_ref.user_string(cx).to_strbuf()
 }
 
-pub fn ty_to_str(cx: &ctxt, typ: t) -> ~str {
-    fn fn_input_to_str(cx: &ctxt, input: ty::t) -> ~str {
-        ty_to_str(cx, input)
+pub fn ty_to_str(cx: &ctxt, typ: t) -> StrBuf {
+    fn fn_input_to_str(cx: &ctxt, input: ty::t) -> StrBuf {
+        ty_to_str(cx, input).to_strbuf()
     }
     fn bare_fn_to_str(cx: &ctxt,
                       fn_style: ast::FnStyle,
                       abi: abi::Abi,
                       ident: Option<ast::Ident>,
                       sig: &ty::FnSig)
-                      -> ~str {
+                      -> StrBuf {
         let mut s = StrBuf::new();
         match fn_style {
             ast::NormalFn => {}
@@ -261,16 +276,16 @@ pub fn ty_to_str(cx: &ctxt, typ: t) -> ~str {
 
         push_sig_to_str(cx, &mut s, '(', ')', sig);
 
-        s.into_owned()
+        s
     }
 
-    fn closure_to_str(cx: &ctxt, cty: &ty::ClosureTy) -> ~str {
+    fn closure_to_str(cx: &ctxt, cty: &ty::ClosureTy) -> StrBuf {
         let mut s = StrBuf::new();
 
         match cty.store {
             ty::UniqTraitStore => {}
             ty::RegionTraitStore(region, _) => {
-                s.push_str(region_to_str(cx, "", true, region));
+                s.push_str(region_to_str(cx, "", true, region).as_slice());
             }
         }
 
@@ -299,10 +314,10 @@ pub fn ty_to_str(cx: &ctxt, typ: t) -> ~str {
 
         if !cty.bounds.is_empty() {
             s.push_str(":");
-            s.push_str(cty.bounds.repr(cx));
+            s.push_str(cty.bounds.repr(cx).as_slice());
         }
 
-        s.into_owned()
+        s
     }
 
     fn push_sig_to_str(cx: &ctxt,
@@ -311,7 +326,7 @@ pub fn ty_to_str(cx: &ctxt, typ: t) -> ~str {
                        ket: char,
                        sig: &ty::FnSig) {
         s.push_char(bra);
-        let strs: Vec<~str> = sig.inputs.iter().map(|a| fn_input_to_str(cx, *a)).collect();
+        let strs: Vec<StrBuf> = sig.inputs.iter().map(|a| fn_input_to_str(cx, *a)).collect();
         s.push_str(strs.connect(", "));
         if sig.variadic {
             s.push_str(", ...");
@@ -323,7 +338,7 @@ pub fn ty_to_str(cx: &ctxt, typ: t) -> ~str {
             if ty::type_is_bot(sig.output) {
                 s.push_char('!');
             } else {
-                s.push_str(ty_to_str(cx, sig.output));
+                s.push_str(ty_to_str(cx, sig.output).as_slice());
             }
         }
     }
@@ -336,22 +351,30 @@ pub fn ty_to_str(cx: &ctxt, typ: t) -> ~str {
 
     // pretty print the structural type representation:
     return match ty::get(typ).sty {
-      ty_nil => "()".to_owned(),
-      ty_bot => "!".to_owned(),
-      ty_bool => "bool".to_owned(),
-      ty_char => "char".to_owned(),
-      ty_int(t) => ast_util::int_ty_to_str(t, None).to_owned(),
-      ty_uint(t) => ast_util::uint_ty_to_str(t, None).to_owned(),
-      ty_float(t) => ast_util::float_ty_to_str(t).to_owned(),
-      ty_box(typ) => "@".to_owned() + ty_to_str(cx, typ),
-      ty_uniq(typ) => "~".to_owned() + ty_to_str(cx, typ),
-      ty_ptr(ref tm) => "*".to_owned() + mt_to_str(cx, tm),
+      ty_nil => "()".to_strbuf(),
+      ty_bot => "!".to_strbuf(),
+      ty_bool => "bool".to_strbuf(),
+      ty_char => "char".to_strbuf(),
+      ty_int(t) => ast_util::int_ty_to_str(t, None),
+      ty_uint(t) => ast_util::uint_ty_to_str(t, None),
+      ty_float(t) => ast_util::float_ty_to_str(t),
+      ty_box(typ) => {
+          ("@".to_owned() + ty_to_str(cx, typ).as_slice()).to_strbuf()
+      }
+      ty_uniq(typ) => {
+          ("~".to_owned() + ty_to_str(cx, typ).as_slice()).to_strbuf()
+      }
+      ty_ptr(ref tm) => {
+          ("*".to_owned() + mt_to_str(cx, tm).as_slice()).to_strbuf()
+      }
       ty_rptr(r, ref tm) => {
-        region_ptr_to_str(cx, r) + mt_to_str(cx, tm)
+          let mut buf = region_ptr_to_str(cx, r);
+          buf.push_str(mt_to_str(cx, tm).as_slice());
+          buf
       }
       ty_tup(ref elems) => {
-        let strs: Vec<~str> = elems.iter().map(|elem| ty_to_str(cx, *elem)).collect();
-        "(".to_owned() + strs.connect(",") + ")"
+        let strs: Vec<StrBuf> = elems.iter().map(|elem| ty_to_str(cx, *elem)).collect();
+        ("(".to_owned() + strs.connect(",") + ")").to_strbuf()
       }
       ty_closure(ref f) => {
           closure_to_str(cx, *f)
@@ -359,26 +382,26 @@ pub fn ty_to_str(cx: &ctxt, typ: t) -> ~str {
       ty_bare_fn(ref f) => {
           bare_fn_to_str(cx, f.fn_style, f.abi, None, &f.sig)
       }
-      ty_infer(infer_ty) => infer_ty.to_str(),
-      ty_err => "[type error]".to_owned(),
+      ty_infer(infer_ty) => infer_ty.to_str().to_strbuf(),
+      ty_err => "[type error]".to_strbuf(),
       ty_param(param_ty {idx: id, def_id: did}) => {
           let ident = match cx.ty_param_defs.borrow().find(&did.node) {
-              Some(def) => token::get_ident(def.ident).get().to_str(),
+              Some(def) => token::get_ident(def.ident).get().to_strbuf(),
               // This can only happen when a type mismatch error happens and
               // the actual type has more type parameters than the expected one.
-              None => format!("<generic \\#{}>", id)
+              None => format_strbuf!("<generic \\#{}>", id)
           };
           if !cx.sess.verbose() {
               ident
           } else {
-            format!("{}:{:?}", ident, did)
+              format_strbuf!("{}:{:?}", ident, did)
           }
       }
-      ty_self(..) => "Self".to_owned(),
+      ty_self(..) => "Self".to_strbuf(),
       ty_enum(did, ref substs) | ty_struct(did, ref substs) => {
         let base = ty::item_path_str(cx, did);
         parameterized(cx,
-                      base,
+                      base.as_slice(),
                       &substs.regions,
                       substs.tps.as_slice(),
                       did,
@@ -388,17 +411,23 @@ pub fn ty_to_str(cx: &ctxt, typ: t) -> ~str {
           def_id: did, ref substs, store, ref bounds
       }) => {
         let base = ty::item_path_str(cx, did);
-        let ty = parameterized(cx, base, &substs.regions,
+        let ty = parameterized(cx, base.as_slice(), &substs.regions,
                                substs.tps.as_slice(), did, true);
         let bound_sep = if bounds.is_empty() { "" } else { ":" };
         let bound_str = bounds.repr(cx);
-        format!("{}{}{}{}", trait_store_to_str(cx, store), ty, bound_sep, bound_str)
+        format_strbuf!("{}{}{}{}",
+                       trait_store_to_str(cx, store),
+                       ty,
+                       bound_sep,
+                       bound_str)
       }
-      ty_str => "str".to_owned(),
+      ty_str => "str".to_strbuf(),
       ty_vec(ref mt, sz) => {
           match sz {
-              Some(n) => format!("[{}, .. {}]", mt_to_str(cx, mt), n),
-              None => format!("[{}]", ty_to_str(cx, mt.ty)),
+              Some(n) => {
+                  format_strbuf!("[{}, .. {}]", mt_to_str(cx, mt), n)
+              }
+              None => format_strbuf!("[{}]", ty_to_str(cx, mt.ty)),
           }
       }
     }
@@ -409,8 +438,8 @@ pub fn parameterized(cx: &ctxt,
                      regions: &ty::RegionSubsts,
                      tps: &[ty::t],
                      did: ast::DefId,
-                     is_trait: bool) -> ~str {
-
+                     is_trait: bool)
+                     -> StrBuf {
     let mut strs = Vec::new();
     match *regions {
         ty::ErasedRegions => { }
@@ -451,72 +480,74 @@ pub fn parameterized(cx: &ctxt,
     }
 
     if strs.len() > 0u {
-        format!("{}<{}>", base, strs.connect(","))
+        format_strbuf!("{}<{}>", base, strs.connect(","))
     } else {
-        format!("{}", base)
+        format_strbuf!("{}", base)
     }
 }
 
-pub fn ty_to_short_str(cx: &ctxt, typ: t) -> ~str {
-    let mut s = typ.repr(cx);
-    if s.len() >= 32u { s = s.slice(0u, 32u).to_owned(); }
+pub fn ty_to_short_str(cx: &ctxt, typ: t) -> StrBuf {
+    let mut s = typ.repr(cx).to_strbuf();
+    if s.len() >= 32u {
+        s = s.as_slice().slice(0u, 32u).to_strbuf();
+    }
     return s;
 }
 
 impl<T:Repr> Repr for Option<T> {
-    fn repr(&self, tcx: &ctxt) -> ~str {
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
         match self {
-            &None => "None".to_owned(),
+            &None => "None".to_strbuf(),
             &Some(ref t) => t.repr(tcx),
         }
     }
 }
 
 impl<T:Repr,U:Repr> Repr for Result<T,U> {
-    fn repr(&self, tcx: &ctxt) -> ~str {
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
         match self {
             &Ok(ref t) => t.repr(tcx),
-            &Err(ref u) => format!("Err({})", u.repr(tcx))
+            &Err(ref u) => format_strbuf!("Err({})", u.repr(tcx))
         }
     }
 }
 
 impl Repr for () {
-    fn repr(&self, _tcx: &ctxt) -> ~str {
-        "()".to_owned()
+    fn repr(&self, _tcx: &ctxt) -> StrBuf {
+        "()".to_strbuf()
     }
 }
 
 impl<T:Repr> Repr for Rc<T> {
-    fn repr(&self, tcx: &ctxt) -> ~str {
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
         (&**self).repr(tcx)
     }
 }
 
 impl<T:Repr> Repr for @T {
-    fn repr(&self, tcx: &ctxt) -> ~str {
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
         (&**self).repr(tcx)
     }
 }
 
 impl<T:Repr> Repr for Box<T> {
-    fn repr(&self, tcx: &ctxt) -> ~str {
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
         (&**self).repr(tcx)
     }
 }
 
-fn repr_vec<T:Repr>(tcx: &ctxt, v: &[T]) -> ~str {
+fn repr_vec<T:Repr>(tcx: &ctxt, v: &[T]) -> StrBuf {
     vec_map_to_str(v, |t| t.repr(tcx))
 }
 
 impl<'a, T:Repr> Repr for &'a [T] {
-    fn repr(&self, tcx: &ctxt) -> ~str {
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
         repr_vec(tcx, *self)
     }
 }
 
 impl<T:Repr> Repr for OwnedSlice<T> {
-    fn repr(&self, tcx: &ctxt) -> ~str {
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
         repr_vec(tcx, self.as_slice())
     }
 }
@@ -524,167 +555,171 @@ impl<T:Repr> Repr for OwnedSlice<T> {
 // This is necessary to handle types like Option<~[T]>, for which
 // autoderef cannot convert the &[T] handler
 impl<T:Repr> Repr for Vec<T> {
-    fn repr(&self, tcx: &ctxt) -> ~str {
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
         repr_vec(tcx, self.as_slice())
     }
 }
 
 impl Repr for ty::TypeParameterDef {
-    fn repr(&self, tcx: &ctxt) -> ~str {
-        format!("TypeParameterDef({:?}, {})",
-                self.def_id,
-                self.bounds.repr(tcx))
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
+        format_strbuf!("TypeParameterDef({:?}, {})",
+                       self.def_id,
+                       self.bounds.repr(tcx))
     }
 }
 
 impl Repr for ty::RegionParameterDef {
-    fn repr(&self, _tcx: &ctxt) -> ~str {
-        format!("RegionParameterDef({}, {:?})",
-                token::get_name(self.name),
-                self.def_id)
+    fn repr(&self, _tcx: &ctxt) -> StrBuf {
+        format_strbuf!("RegionParameterDef({}, {:?})",
+                       token::get_name(self.name),
+                       self.def_id)
     }
 }
 
 impl Repr for ty::t {
-    fn repr(&self, tcx: &ctxt) -> ~str {
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
         ty_to_str(tcx, *self)
     }
 }
 
 impl Repr for ty::substs {
-    fn repr(&self, tcx: &ctxt) -> ~str {
-        format!("substs(regions={}, self_ty={}, tps={})",
-             self.regions.repr(tcx),
-             self.self_ty.repr(tcx),
-             self.tps.repr(tcx))
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
+        format_strbuf!("substs(regions={}, self_ty={}, tps={})",
+                       self.regions.repr(tcx),
+                       self.self_ty.repr(tcx),
+                       self.tps.repr(tcx))
     }
 }
 
 impl Repr for ty::ItemSubsts {
-    fn repr(&self, tcx: &ctxt) -> ~str {
-        format!("ItemSubsts({})", self.substs.repr(tcx))
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
+        format_strbuf!("ItemSubsts({})", self.substs.repr(tcx))
     }
 }
 
 impl Repr for ty::RegionSubsts {
-    fn repr(&self, tcx: &ctxt) -> ~str {
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
         match *self {
-            ty::ErasedRegions => "erased".to_owned(),
+            ty::ErasedRegions => "erased".to_strbuf(),
             ty::NonerasedRegions(ref regions) => regions.repr(tcx)
         }
     }
 }
 
 impl Repr for ty::ParamBounds {
-    fn repr(&self, tcx: &ctxt) -> ~str {
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
         let mut res = Vec::new();
         for b in self.builtin_bounds.iter() {
             res.push(match b {
-                ty::BoundStatic => "'static".to_owned(),
-                ty::BoundSend => "Send".to_owned(),
-                ty::BoundSized => "Sized".to_owned(),
-                ty::BoundCopy => "Copy".to_owned(),
-                ty::BoundShare => "Share".to_owned(),
+                ty::BoundStatic => "'static".to_strbuf(),
+                ty::BoundSend => "Send".to_strbuf(),
+                ty::BoundSized => "Sized".to_strbuf(),
+                ty::BoundCopy => "Copy".to_strbuf(),
+                ty::BoundShare => "Share".to_strbuf(),
             });
         }
         for t in self.trait_bounds.iter() {
             res.push(t.repr(tcx));
         }
-        res.connect("+")
+        res.connect("+").to_strbuf()
     }
 }
 
 impl Repr for ty::TraitRef {
-    fn repr(&self, tcx: &ctxt) -> ~str {
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
         trait_ref_to_str(tcx, self)
     }
 }
 
 impl Repr for ast::Expr {
-    fn repr(&self, _tcx: &ctxt) -> ~str {
-        format!("expr({}: {})", self.id, pprust::expr_to_str(self))
+    fn repr(&self, _tcx: &ctxt) -> StrBuf {
+        format_strbuf!("expr({}: {})", self.id, pprust::expr_to_str(self))
     }
 }
 
 impl Repr for ast::Item {
-    fn repr(&self, tcx: &ctxt) -> ~str {
-        format!("item({})", tcx.map.node_to_str(self.id))
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
+        format_strbuf!("item({})", tcx.map.node_to_str(self.id))
     }
 }
 
 impl Repr for ast::Stmt {
-    fn repr(&self, _tcx: &ctxt) -> ~str {
-        format!("stmt({}: {})",
-                ast_util::stmt_id(self),
-                pprust::stmt_to_str(self))
+    fn repr(&self, _tcx: &ctxt) -> StrBuf {
+        format_strbuf!("stmt({}: {})",
+                       ast_util::stmt_id(self),
+                       pprust::stmt_to_str(self))
     }
 }
 
 impl Repr for ast::Pat {
-    fn repr(&self, _tcx: &ctxt) -> ~str {
-        format!("pat({}: {})",
-             self.id,
-             pprust::pat_to_str(self))
+    fn repr(&self, _tcx: &ctxt) -> StrBuf {
+        format_strbuf!("pat({}: {})", self.id, pprust::pat_to_str(self))
     }
 }
 
 impl Repr for ty::BoundRegion {
-    fn repr(&self, tcx: &ctxt) -> ~str {
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
         match *self {
-            ty::BrAnon(id) => format!("BrAnon({})", id),
-            ty::BrNamed(id, name) => format!("BrNamed({}, {})",
-                                             id.repr(tcx),
-                                             token::get_name(name)),
-            ty::BrFresh(id) => format!("BrFresh({})", id),
+            ty::BrAnon(id) => format_strbuf!("BrAnon({})", id),
+            ty::BrNamed(id, name) => {
+                format_strbuf!("BrNamed({}, {})",
+                               id.repr(tcx),
+                               token::get_name(name))
+            }
+            ty::BrFresh(id) => format_strbuf!("BrFresh({})", id),
         }
     }
 }
 
 impl Repr for ty::Region {
-    fn repr(&self, tcx: &ctxt) -> ~str {
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
         match *self {
             ty::ReEarlyBound(id, index, name) => {
-                format!("ReEarlyBound({}, {}, {})",
-                        id, index, token::get_name(name))
+                format_strbuf!("ReEarlyBound({}, {}, {})",
+                               id,
+                               index,
+                               token::get_name(name))
             }
 
             ty::ReLateBound(binder_id, ref bound_region) => {
-                format!("ReLateBound({}, {})",
-                        binder_id, bound_region.repr(tcx))
+                format_strbuf!("ReLateBound({}, {})",
+                               binder_id,
+                               bound_region.repr(tcx))
             }
 
             ty::ReFree(ref fr) => {
-                format!("ReFree({}, {})",
-                        fr.scope_id,
-                        fr.bound_region.repr(tcx))
+                format_strbuf!("ReFree({}, {})",
+                               fr.scope_id,
+                               fr.bound_region.repr(tcx))
             }
 
             ty::ReScope(id) => {
-                format!("ReScope({})", id)
+                format_strbuf!("ReScope({})", id)
             }
 
             ty::ReStatic => {
-                format!("ReStatic")
+                "ReStatic".to_strbuf()
             }
 
             ty::ReInfer(ReVar(ref vid)) => {
-                format!("ReInfer({})", vid.id)
+                format_strbuf!("ReInfer({})", vid.id)
             }
 
             ty::ReInfer(ReSkolemized(id, ref bound_region)) => {
-                format!("re_skolemized({}, {})",
-                        id, bound_region.repr(tcx))
+                format_strbuf!("re_skolemized({}, {})",
+                               id,
+                               bound_region.repr(tcx))
             }
 
             ty::ReEmpty => {
-                format!("ReEmpty")
+                "ReEmpty".to_strbuf()
             }
         }
     }
 }
 
 impl Repr for ast::DefId {
-    fn repr(&self, tcx: &ctxt) -> ~str {
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
         // Unfortunately, there seems to be no way to attempt to print
         // a path for a def-id, so I'll just make a best effort for now
         // and otherwise fallback to just printing the crate/node pair
@@ -697,115 +732,119 @@ impl Repr for ast::DefId {
                     Some(ast_map::NodeTraitMethod(..)) |
                     Some(ast_map::NodeVariant(..)) |
                     Some(ast_map::NodeStructCtor(..)) => {
-                        return format!("{:?}:{}",
-                                       *self,
-                                       ty::item_path_str(tcx, *self));
+                        return format_strbuf!(
+                                "{:?}:{}",
+                                *self,
+                                ty::item_path_str(tcx, *self))
                     }
                     _ => {}
                 }
             }
         }
-        return format!("{:?}", *self);
+        return format_strbuf!("{:?}", *self)
     }
 }
 
 impl Repr for ty::ty_param_bounds_and_ty {
-    fn repr(&self, tcx: &ctxt) -> ~str {
-        format!("ty_param_bounds_and_ty \\{generics: {}, ty: {}\\}",
-             self.generics.repr(tcx),
-             self.ty.repr(tcx))
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
+        format_strbuf!("ty_param_bounds_and_ty \\{generics: {}, ty: {}\\}",
+                       self.generics.repr(tcx),
+                       self.ty.repr(tcx))
     }
 }
 
 impl Repr for ty::Generics {
-    fn repr(&self, tcx: &ctxt) -> ~str {
-        format!("Generics(type_param_defs: {}, region_param_defs: {})",
-                self.type_param_defs().repr(tcx),
-                self.region_param_defs().repr(tcx))
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
+        format_strbuf!("Generics(type_param_defs: {}, \
+                           region_param_defs: {})",
+                 self.type_param_defs().repr(tcx),
+                 self.region_param_defs().repr(tcx))
     }
 }
 
 impl Repr for ty::ItemVariances {
-    fn repr(&self, tcx: &ctxt) -> ~str {
-        format!("IterVariances(self_param={}, type_params={}, region_params={})",
-                self.self_param.repr(tcx),
-                self.type_params.repr(tcx),
-                self.region_params.repr(tcx))
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
+        format_strbuf!("IterVariances(self_param={}, \
+                                type_params={}, \
+                                region_params={})",
+                 self.self_param.repr(tcx),
+                 self.type_params.repr(tcx),
+                 self.region_params.repr(tcx))
     }
 }
 
 impl Repr for ty::Variance {
-    fn repr(&self, _: &ctxt) -> ~str {
-        self.to_str().to_owned()
+    fn repr(&self, _: &ctxt) -> StrBuf {
+        self.to_str().to_strbuf()
     }
 }
 
 impl Repr for ty::Method {
-    fn repr(&self, tcx: &ctxt) -> ~str {
-        format!("method(ident: {}, generics: {}, fty: {}, \
-                explicit_self: {}, vis: {}, def_id: {})",
-                self.ident.repr(tcx),
-                self.generics.repr(tcx),
-                self.fty.repr(tcx),
-                self.explicit_self.repr(tcx),
-                self.vis.repr(tcx),
-                self.def_id.repr(tcx))
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
+        format_strbuf!("method(ident: {}, generics: {}, fty: {}, \
+                        explicit_self: {}, vis: {}, def_id: {})",
+                       self.ident.repr(tcx),
+                       self.generics.repr(tcx),
+                       self.fty.repr(tcx),
+                       self.explicit_self.repr(tcx),
+                       self.vis.repr(tcx),
+                       self.def_id.repr(tcx))
     }
 }
 
 impl Repr for ast::Name {
-    fn repr(&self, _tcx: &ctxt) -> ~str {
-        token::get_name(*self).get().to_str()
+    fn repr(&self, _tcx: &ctxt) -> StrBuf {
+        token::get_name(*self).get().to_strbuf()
     }
 }
 
 impl Repr for ast::Ident {
-    fn repr(&self, _tcx: &ctxt) -> ~str {
-        token::get_ident(*self).get().to_str()
+    fn repr(&self, _tcx: &ctxt) -> StrBuf {
+        token::get_ident(*self).get().to_strbuf()
     }
 }
 
 impl Repr for ast::ExplicitSelf_ {
-    fn repr(&self, _tcx: &ctxt) -> ~str {
-        format!("{:?}", *self)
+    fn repr(&self, _tcx: &ctxt) -> StrBuf {
+        format_strbuf!("{:?}", *self)
     }
 }
 
 impl Repr for ast::Visibility {
-    fn repr(&self, _tcx: &ctxt) -> ~str {
-        format!("{:?}", *self)
+    fn repr(&self, _tcx: &ctxt) -> StrBuf {
+        format_strbuf!("{:?}", *self)
     }
 }
 
 impl Repr for ty::BareFnTy {
-    fn repr(&self, tcx: &ctxt) -> ~str {
-        format!("BareFnTy \\{fn_style: {:?}, abi: {}, sig: {}\\}",
-             self.fn_style,
-             self.abi.to_str(),
-             self.sig.repr(tcx))
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
+        format_strbuf!("BareFnTy \\{fn_style: {:?}, abi: {}, sig: {}\\}",
+                       self.fn_style,
+                       self.abi.to_str(),
+                       self.sig.repr(tcx))
     }
 }
 
 impl Repr for ty::FnSig {
-    fn repr(&self, tcx: &ctxt) -> ~str {
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
         fn_sig_to_str(tcx, self)
     }
 }
 
 impl Repr for typeck::MethodCallee {
-    fn repr(&self, tcx: &ctxt) -> ~str {
-        format!("MethodCallee \\{origin: {}, ty: {}, {}\\}",
-            self.origin.repr(tcx),
-            self.ty.repr(tcx),
-            self.substs.repr(tcx))
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
+        format_strbuf!("MethodCallee \\{origin: {}, ty: {}, {}\\}",
+                       self.origin.repr(tcx),
+                       self.ty.repr(tcx),
+                       self.substs.repr(tcx))
     }
 }
 
 impl Repr for typeck::MethodOrigin {
-    fn repr(&self, tcx: &ctxt) -> ~str {
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
         match self {
             &typeck::MethodStatic(def_id) => {
-                format!("MethodStatic({})", def_id.repr(tcx))
+                format_strbuf!("MethodStatic({})", def_id.repr(tcx))
             }
             &typeck::MethodParam(ref p) => {
                 p.repr(tcx)
@@ -818,144 +857,156 @@ impl Repr for typeck::MethodOrigin {
 }
 
 impl Repr for typeck::MethodParam {
-    fn repr(&self, tcx: &ctxt) -> ~str {
-        format!("MethodParam({},{:?},{:?},{:?})",
-             self.trait_id.repr(tcx),
-             self.method_num,
-             self.param_num,
-             self.bound_num)
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
+        format_strbuf!("MethodParam({},{:?},{:?},{:?})",
+                       self.trait_id.repr(tcx),
+                       self.method_num,
+                       self.param_num,
+                       self.bound_num)
     }
 }
 
 impl Repr for typeck::MethodObject {
-    fn repr(&self, tcx: &ctxt) -> ~str {
-        format!("MethodObject({},{:?},{:?})",
-             self.trait_id.repr(tcx),
-             self.method_num,
-             self.real_index)
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
+        format_strbuf!("MethodObject({},{:?},{:?})",
+                       self.trait_id.repr(tcx),
+                       self.method_num,
+                       self.real_index)
     }
 }
 
 
 impl Repr for ty::RegionVid {
-    fn repr(&self, _tcx: &ctxt) -> ~str {
-        format!("{:?}", *self)
+    fn repr(&self, _tcx: &ctxt) -> StrBuf {
+        format_strbuf!("{:?}", *self)
     }
 }
 
 impl Repr for ty::TraitStore {
-    fn repr(&self, tcx: &ctxt) -> ~str {
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
         trait_store_to_str(tcx, *self)
     }
 }
 
 impl Repr for ty::BuiltinBound {
-    fn repr(&self, _tcx: &ctxt) -> ~str {
-        format!("{:?}", *self)
+    fn repr(&self, _tcx: &ctxt) -> StrBuf {
+        format_strbuf!("{:?}", *self)
     }
 }
 
 impl UserString for ty::BuiltinBound {
-    fn user_string(&self, _tcx: &ctxt) -> ~str {
+    fn user_string(&self, _tcx: &ctxt) -> StrBuf {
         match *self {
-            ty::BoundStatic => "'static".to_owned(),
-            ty::BoundSend => "Send".to_owned(),
-            ty::BoundSized => "Sized".to_owned(),
-            ty::BoundCopy => "Copy".to_owned(),
-            ty::BoundShare => "Share".to_owned(),
+            ty::BoundStatic => "'static".to_strbuf(),
+            ty::BoundSend => "Send".to_strbuf(),
+            ty::BoundSized => "Sized".to_strbuf(),
+            ty::BoundCopy => "Copy".to_strbuf(),
+            ty::BoundShare => "Share".to_strbuf(),
         }
     }
 }
 
 impl Repr for ty::BuiltinBounds {
-    fn repr(&self, tcx: &ctxt) -> ~str {
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
         self.user_string(tcx)
     }
 }
 
 impl Repr for Span {
-    fn repr(&self, tcx: &ctxt) -> ~str {
-        tcx.sess.codemap().span_to_str(*self).to_owned()
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
+        tcx.sess.codemap().span_to_str(*self).to_strbuf()
     }
 }
 
 impl<A:UserString> UserString for Rc<A> {
-    fn user_string(&self, tcx: &ctxt) -> ~str {
+    fn user_string(&self, tcx: &ctxt) -> StrBuf {
         let this: &A = &**self;
         this.user_string(tcx)
     }
 }
 
 impl UserString for ty::BuiltinBounds {
-    fn user_string(&self, tcx: &ctxt) -> ~str {
-        self.iter().map(|bb| bb.user_string(tcx)).collect::<Vec<~str>>().connect("+")
+    fn user_string(&self, tcx: &ctxt) -> StrBuf {
+        self.iter()
+            .map(|bb| bb.user_string(tcx))
+            .collect::<Vec<StrBuf>>()
+            .connect("+")
+            .to_strbuf()
     }
 }
 
 impl UserString for ty::TraitRef {
-    fn user_string(&self, tcx: &ctxt) -> ~str {
+    fn user_string(&self, tcx: &ctxt) -> StrBuf {
         let base = ty::item_path_str(tcx, self.def_id);
         if tcx.sess.verbose() && self.substs.self_ty.is_some() {
             let mut all_tps = self.substs.tps.clone();
             for &t in self.substs.self_ty.iter() { all_tps.push(t); }
-            parameterized(tcx, base, &self.substs.regions,
-                          all_tps.as_slice(), self.def_id, true)
+            parameterized(tcx,
+                          base.as_slice(),
+                          &self.substs.regions,
+                          all_tps.as_slice(),
+                          self.def_id,
+                          true)
         } else {
-            parameterized(tcx, base, &self.substs.regions,
-                          self.substs.tps.as_slice(), self.def_id, true)
+            parameterized(tcx,
+                          base.as_slice(),
+                          &self.substs.regions,
+                          self.substs.tps.as_slice(),
+                          self.def_id,
+                          true)
         }
     }
 }
 
 impl UserString for ty::t {
-    fn user_string(&self, tcx: &ctxt) -> ~str {
+    fn user_string(&self, tcx: &ctxt) -> StrBuf {
         ty_to_str(tcx, *self)
     }
 }
 
 impl UserString for ast::Ident {
-    fn user_string(&self, _tcx: &ctxt) -> ~str {
-        token::get_name(self.name).get().to_owned()
+    fn user_string(&self, _tcx: &ctxt) -> StrBuf {
+        token::get_name(self.name).get().to_strbuf()
     }
 }
 
 impl Repr for abi::Abi {
-    fn repr(&self, _tcx: &ctxt) -> ~str {
-        self.to_str()
+    fn repr(&self, _tcx: &ctxt) -> StrBuf {
+        self.to_str().to_strbuf()
     }
 }
 
 impl UserString for abi::Abi {
-    fn user_string(&self, _tcx: &ctxt) -> ~str {
-        self.to_str()
+    fn user_string(&self, _tcx: &ctxt) -> StrBuf {
+        self.to_str().to_strbuf()
     }
 }
 
 impl Repr for ty::UpvarId {
-    fn repr(&self, tcx: &ctxt) -> ~str {
-        format!("UpvarId({};`{}`;{})",
-             self.var_id,
-             ty::local_var_name_str(tcx, self.var_id),
-             self.closure_expr_id)
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
+        format_strbuf!("UpvarId({};`{}`;{})",
+                       self.var_id,
+                       ty::local_var_name_str(tcx, self.var_id),
+                       self.closure_expr_id)
     }
 }
 
 impl Repr for ast::Mutability {
-    fn repr(&self, _tcx: &ctxt) -> ~str {
-        format!("{:?}", *self)
+    fn repr(&self, _tcx: &ctxt) -> StrBuf {
+        format_strbuf!("{:?}", *self)
     }
 }
 
 impl Repr for ty::BorrowKind {
-    fn repr(&self, _tcx: &ctxt) -> ~str {
-        format!("{:?}", *self)
+    fn repr(&self, _tcx: &ctxt) -> StrBuf {
+        format_strbuf!("{:?}", *self)
     }
 }
 
 impl Repr for ty::UpvarBorrow {
-    fn repr(&self, tcx: &ctxt) -> ~str {
-        format!("UpvarBorrow({}, {})",
-             self.kind.repr(tcx),
-             self.region.repr(tcx))
+    fn repr(&self, tcx: &ctxt) -> StrBuf {
+        format_strbuf!("UpvarBorrow({}, {})",
+                       self.kind.repr(tcx),
+                       self.region.repr(tcx))
     }
 }
diff --git a/src/librustc/util/sha2.rs b/src/librustc/util/sha2.rs
index 16faccbc9c2e4..a71ae83e73626 100644
--- a/src/librustc/util/sha2.rs
+++ b/src/librustc/util/sha2.rs
@@ -257,9 +257,9 @@ pub trait Digest {
     }
 
     /// Convenience function that retrieves the result of a digest as a
-    /// ~str in hexadecimal format.
-    fn result_str(&mut self) -> ~str {
-        self.result_bytes().as_slice().to_hex()
+    /// StrBuf in hexadecimal format.
+    fn result_str(&mut self) -> StrBuf {
+        self.result_bytes().as_slice().to_hex().to_strbuf()
     }
 }
 
@@ -543,15 +543,15 @@ mod tests {
     }
 
     struct Test {
-        input: ~str,
-        output_str: ~str,
+        input: StrBuf,
+        output_str: StrBuf,
     }
 
     fn test_hash<D: Digest>(sh: &mut D, tests: &[Test]) {
         // Test that it works when accepting the message all at once
         for t in tests.iter() {
             sh.reset();
-            sh.input_str(t.input);
+            sh.input_str(t.input.as_slice());
             let out_str = sh.result_str();
             assert!(out_str == t.output_str);
         }
@@ -563,7 +563,9 @@ mod tests {
             let mut left = len;
             while left > 0u {
                 let take = (left + 1u) / 2u;
-                sh.input_str(t.input.slice(len - left, take + len - left));
+                sh.input_str(t.input
+                              .as_slice()
+                              .slice(len - left, take + len - left));
                 left = left - take;
             }
             let out_str = sh.result_str();
@@ -576,19 +578,21 @@ mod tests {
         // Examples from wikipedia
         let wikipedia_tests = vec!(
             Test {
-                input: "".to_owned(),
+                input: "".to_strbuf(),
                 output_str: "e3b0c44298fc1c149afb\
-            f4c8996fb92427ae41e4649b934ca495991b7852b855".to_owned()
+            f4c8996fb92427ae41e4649b934ca495991b7852b855".to_strbuf()
             },
             Test {
-                input: "The quick brown fox jumps over the lazy dog".to_owned(),
+                input: "The quick brown fox jumps over the lazy \
+                        dog".to_strbuf(),
                 output_str: "d7a8fbb307d7809469ca\
-            9abcb0082e4f8d5651e46d3cdb762d02d0bf37c9e592".to_owned()
+            9abcb0082e4f8d5651e46d3cdb762d02d0bf37c9e592".to_strbuf()
             },
             Test {
-                input: "The quick brown fox jumps over the lazy dog.".to_owned(),
+                input: "The quick brown fox jumps over the lazy \
+                        dog.".to_strbuf(),
                 output_str: "ef537f25c895bfa78252\
-            6529a9b63d97aa631564d5d789c2b765448c8635fb6c".to_owned()
+            6529a9b63d97aa631564d5d789c2b765448c8635fb6c".to_strbuf()
             });
 
         let tests = wikipedia_tests;
diff --git a/src/librustdoc/clean.rs b/src/librustdoc/clean.rs
index aef289a4a7f39..bbc1047ed1ef5 100644
--- a/src/librustdoc/clean.rs
+++ b/src/librustdoc/clean.rs
@@ -90,7 +90,7 @@ impl<'a> Clean<Crate> for visit_ast::RustdocVisitor<'a> {
                                                        self.attrs.as_slice(),
                                                        cx.sess());
         let id = link::find_crate_id(self.attrs.as_slice(),
-                                     t_outputs.out_filestem);
+                                     t_outputs.out_filestem.as_slice());
         Crate {
             name: id.name.to_owned(),
             module: Some(self.module.clean()),
diff --git a/src/librustdoc/test.rs b/src/librustdoc/test.rs
index 8a631fdcdd08c..fe80bc6c47957 100644
--- a/src/librustdoc/test.rs
+++ b/src/librustdoc/test.rs
@@ -100,7 +100,7 @@ pub fn run(input: &str,
 fn runtest(test: &str, cratename: &str, libs: HashSet<Path>, should_fail: bool,
            no_run: bool, loose_feature_gating: bool) {
     let test = maketest(test, cratename, loose_feature_gating);
-    let input = driver::StrInput(test);
+    let input = driver::StrInput(test.to_strbuf());
 
     let sessopts = config::Options {
         maybe_sysroot: Some(os::self_exe_path().unwrap().dir_path()),
diff --git a/src/libstd/fmt/mod.rs b/src/libstd/fmt/mod.rs
index b4bb6236f08ab..fecd68e049a6f 100644
--- a/src/libstd/fmt/mod.rs
+++ b/src/libstd/fmt/mod.rs
@@ -504,6 +504,7 @@ use slice::{Vector, ImmutableVector};
 use slice;
 use str::{StrSlice, StrAllocating, UTF16Item, ScalarValue, LoneSurrogate};
 use str;
+use strbuf::StrBuf;
 
 pub use self::num::radix;
 pub use self::num::Radix;
@@ -788,6 +789,11 @@ pub fn format(args: &Arguments) -> ~str {
     unsafe { format_unsafe(args.fmt, args.args) }
 }
 
+/// Temporary transitionary thing.
+pub fn format_strbuf(args: &Arguments) -> StrBuf {
+    unsafe { format_unsafe_strbuf(args.fmt, args.args) }
+}
+
 /// The unsafe version of the formatting function.
 ///
 /// This is currently an unsafe function because the types of all arguments
@@ -815,6 +821,14 @@ pub unsafe fn format_unsafe(fmt: &[rt::Piece], args: &[Argument]) -> ~str {
     return str::from_utf8(output.unwrap().as_slice()).unwrap().to_owned();
 }
 
+/// Temporary transitionary thing.
+pub unsafe fn format_unsafe_strbuf(fmt: &[rt::Piece], args: &[Argument])
+                                   -> StrBuf {
+    let mut output = MemWriter::new();
+    write_unsafe(&mut output as &mut io::Writer, fmt, args).unwrap();
+    return str::from_utf8(output.unwrap().as_slice()).unwrap().into_strbuf();
+}
+
 impl<'a> Formatter<'a> {
 
     // First up is the collection of functions used to execute a format string
diff --git a/src/libstd/macros.rs b/src/libstd/macros.rs
index 1efe56756edde..3a0e78b39d13d 100644
--- a/src/libstd/macros.rs
+++ b/src/libstd/macros.rs
@@ -229,6 +229,14 @@ macro_rules! format(
     )
 )
 
+/// Temporary transitionary thing.
+#[macro_export]
+macro_rules! format_strbuf(
+    ($($arg:tt)*) => (
+        format_args!(::std::fmt::format_strbuf, $($arg)*)
+    )
+)
+
 /// Use the `format!` syntax to write data into a buffer of type `&mut Writer`.
 /// See `std::fmt` for more information.
 ///