auto merge of #13107 : seanmonstar/rust/encoder-errors, r=erickt

All of Decoder and Encoder's methods now return a Result.

Encodable.encode() and Decodable.decode() return a Result as well.

fixes #12292

Author: bors

src/librustc/driver/driver.rs

@@ -168,6 +168,18 @@ impl Input {
     }
 }
 
+// FIXME: remove unwrap_ after snapshot
+#[cfg(stage0)]
+fn unwrap_<T>(t: T) -> T {
+    t
+}
+
+#[cfg(not(stage0))]
+fn unwrap_<T, E>(r: Result<T, E>) -> T {
+    r.unwrap()
+}
+
+
 pub fn phase_1_parse_input(sess: &Session, cfg: ast::CrateConfig, input: &Input)
     -> ast::Crate {
     let krate = time(sess.time_passes(), "parsing", (), |_| {
@@ -187,7 +199,8 @@ pub fn phase_1_parse_input(sess: &Session, cfg: ast::CrateConfig, input: &Input)
     if sess.opts.debugging_opts & session::AST_JSON_NOEXPAND != 0 {
         let mut stdout = io::BufferedWriter::new(io::stdout());
         let mut json = json::PrettyEncoder::new(&mut stdout);
-        krate.encode(&mut json);
+        // unwrapping so IoError isn't ignored
+        unwrap_(krate.encode(&mut json));
     }
 
     if sess.show_span() {
@@ -262,7 +275,8 @@ pub fn phase_2_configure_and_expand(sess: &Session,
     if sess.opts.debugging_opts & session::AST_JSON != 0 {
         let mut stdout = io::BufferedWriter::new(io::stdout());
         let mut json = json::PrettyEncoder::new(&mut stdout);
-        krate.encode(&mut json);
+        // unwrapping so IoError isn't ignored
+        unwrap_(krate.encode(&mut json));
     }
 
     (krate, map)

src/librustc/metadata/decoder.rs

@@ -47,6 +47,17 @@ use syntax::crateid::CrateId;
 
 pub type Cmd = @crate_metadata;
 
+// FIXME: remove unwrap_ after a snapshot
+#[cfg(stage0)]
+fn unwrap_<T>(t: T) -> T {
+    t
+}
+
+#[cfg(not(stage0))]
+fn unwrap_<T, E>(r: Result<T, E>) -> T {
+    r.unwrap()
+}
+
 // A function that takes a def_id relative to the crate being searched and
 // returns a def_id relative to the compilation environment, i.e. if we hit a
 // def_id for an item defined in another crate, somebody needs to figure out
@@ -59,15 +70,15 @@ fn lookup_hash<'a>(d: ebml::Doc<'a>, eq_fn: |&[u8]| -> bool,
     let table = reader::get_doc(index, tag_index_table);
     let hash_pos = table.start + (hash % 256 * 4) as uint;
     let pos = u64_from_be_bytes(d.data, hash_pos, 4) as uint;
-    let tagged_doc = reader::doc_at(d.data, pos);
+    let tagged_doc = unwrap_(reader::doc_at(d.data, pos));
 
     let belt = tag_index_buckets_bucket_elt;
 
     let mut ret = None;
     reader::tagged_docs(tagged_doc.doc, belt, |elt| {
         let pos = u64_from_be_bytes(elt.data, elt.start, 4) as uint;
         if eq_fn(elt.data.slice(elt.start + 4, elt.end)) {
-            ret = Some(reader::doc_at(d.data, pos).doc);
+            ret = Some(unwrap_(reader::doc_at(d.data, pos)).doc);
             false
         } else {
             true
@@ -853,7 +864,7 @@ pub fn get_item_variances(cdata: Cmd, id: ast::NodeId) -> ty::ItemVariances {
     let item_doc = lookup_item(id, data);
     let variance_doc = reader::get_doc(item_doc, tag_item_variances);
     let mut decoder = reader::Decoder(variance_doc);
-    Decodable::decode(&mut decoder)
+    unwrap_(Decodable::decode(&mut decoder))
 }
 
 pub fn get_provided_trait_methods(intr: @IdentInterner, cdata: Cmd,