diff --git a/RELEASES.md b/RELEASES.md
index a747d04696821..95307ab788e57 100644
--- a/RELEASES.md
+++ b/RELEASES.md
@@ -1,3 +1,30 @@
+Version 1.12.1 (2016-10-20)
+===========================
+
+Regression Fixes
+----------------
+
+* [ICE: 'rustc' panicked at 'assertion failed: concrete_substs.is_normalized_for_trans()' #36381][36381]
+* [Confusion with double negation and booleans][36856]
+* [rustc 1.12.0 fails with SIGSEGV in release mode (syn crate 0.8.0)][36875]
+* [Rustc 1.12.0 Windows build of `ethcore` crate fails with LLVM error][36924]
+* [1.12.0: High memory usage when linking in release mode with debug info][36926]
+* [Corrupted memory after updated to 1.12][36936]
+* ["Let NullaryConstructor = something;" causes internal compiler error: "tried to overwrite interned AdtDef"][37026]
+* [Fix ICE: inject bitcast if types mismatch for invokes/calls/stores][37112]
+* [debuginfo: Handle spread_arg case in MIR-trans in a more stable way.][37153]
+
+[36381]: https://github.com/rust-lang/rust/issues/36381
+[36856]: https://github.com/rust-lang/rust/issues/36856
+[36875]: https://github.com/rust-lang/rust/issues/36875
+[36924]: https://github.com/rust-lang/rust/issues/36924
+[36926]: https://github.com/rust-lang/rust/issues/36926
+[36936]: https://github.com/rust-lang/rust/issues/36936
+[37026]: https://github.com/rust-lang/rust/issues/37026
+[37112]: https://github.com/rust-lang/rust/issues/37112
+[37153]: https://github.com/rust-lang/rust/issues/37153
+
+
 Version 1.12.0 (2016-09-29)
 ===========================
 
diff --git a/mk/main.mk b/mk/main.mk
index 80f1fdfab96fe..8d95bf6ed8daf 100644
--- a/mk/main.mk
+++ b/mk/main.mk
@@ -18,7 +18,7 @@ CFG_RELEASE_NUM=1.13.0
 # An optional number to put after the label, e.g. '.2' -> '-beta.2'
 # NB Make sure it starts with a dot to conform to semver pre-release
 # versions (section 9)
-CFG_PRERELEASE_VERSION=.2
+CFG_PRERELEASE_VERSION=.3
 
 ifeq ($(CFG_RELEASE_CHANNEL),stable)
 # This is the normal semver version string, e.g. "0.12.0", "0.12.0-nightly"
@@ -53,17 +53,6 @@ endif
 # versions in the same place
 CFG_FILENAME_EXTRA=$(shell printf '%s' $(CFG_RELEASE)$(CFG_EXTRA_FILENAME) | $(CFG_HASH_COMMAND))
 
-# A magic value that allows the compiler to use unstable features during the
-# bootstrap even when doing so would normally be an error because of feature
-# staging or because the build turns on warnings-as-errors and unstable features
-# default to warnings. The build has to match this key in an env var.
-#
-# This value is keyed off the release to ensure that all compilers for one
-# particular release have the same bootstrap key. Note that this is
-# intentionally not "secure" by any definition, this is largely just a deterrent
-# from users enabling unstable features on the stable compiler.
-CFG_BOOTSTRAP_KEY=$(CFG_FILENAME_EXTRA)
-
 # If local-rust is the same as the current version, then force a local-rebuild
 ifdef CFG_ENABLE_LOCAL_RUST
 ifeq ($(CFG_RELEASE),\
@@ -73,14 +62,6 @@ ifeq ($(CFG_RELEASE),\
 endif
 endif
 
-# The stage0 compiler needs to use the previous key recorded in src/stage0.txt,
-# except for local-rebuild when it just uses the same current key.
-ifdef CFG_ENABLE_LOCAL_REBUILD
-CFG_BOOTSTRAP_KEY_STAGE0=$(CFG_BOOTSTRAP_KEY)
-else
-CFG_BOOTSTRAP_KEY_STAGE0=$(shell sed -ne 's/^rustc_key: //p' $(S)src/stage0.txt)
-endif
-
 # The name of the package to use for creating tarballs, installers etc.
 CFG_PACKAGE_NAME=rustc-$(CFG_PACKAGE_VERS)
 
@@ -387,13 +368,16 @@ CFG_INFO := $(info cfg: disabling unstable features (CFG_DISABLE_UNSTABLE_FEATUR
 # Turn on feature-staging
 export CFG_DISABLE_UNSTABLE_FEATURES
 # Subvert unstable feature lints to do the self-build
-export RUSTC_BOOTSTRAP_KEY:=$(CFG_BOOTSTRAP_KEY)
+export RUSTC_BOOTSTRAP
 endif
-export CFG_BOOTSTRAP_KEY
 ifdef CFG_MUSL_ROOT
 export CFG_MUSL_ROOT
 endif
 
+# FIXME: Transitionary measure to bootstrap using the old bootstrap logic.
+# Remove this once the bootstrap compiler uses the new login in Issue #36548.
+export RUSTC_BOOTSTRAP_KEY=5c6cf767
+
 ######################################################################
 # Per-stage targets and runner
 ######################################################################
diff --git a/mk/target.mk b/mk/target.mk
index 2a08b7b046534..1b139909ab458 100644
--- a/mk/target.mk
+++ b/mk/target.mk
@@ -42,23 +42,6 @@ $(foreach host,$(CFG_HOST), \
    $(foreach crate,$(CRATES), \
     $(eval $(call RUST_CRATE_FULLDEPS,$(stage),$(target),$(host),$(crate)))))))
 
-# $(1) stage
-# $(2) target
-# $(3) host
-define DEFINE_BOOTSTRAP_KEY
-BOOTSTRAP_KEY$(1)_T_$(2)_H_$(3) := $$(CFG_BOOTSTRAP_KEY)
-ifeq ($(1),0)
-ifeq ($(3),$$(CFG_BUILD))
-BOOTSTRAP_KEY$(1)_T_$(2)_H_$(3) := $$(CFG_BOOTSTRAP_KEY_STAGE0)
-endif
-endif
-endef
-
-$(foreach host,$(CFG_TARGET), \
- $(foreach target,$(CFG_TARGET), \
-  $(foreach stage,$(STAGES), \
-   $(eval $(call DEFINE_BOOTSTRAP_KEY,$(stage),$(target),$(host))))))
-
 # RUST_TARGET_STAGE_N template: This defines how target artifacts are built
 # for all stage/target architecture combinations. This is one giant rule which
 # works as follows:
@@ -83,8 +66,6 @@ $(foreach host,$(CFG_TARGET), \
 define RUST_TARGET_STAGE_N
 
 $$(TLIB$(1)_T_$(2)_H_$(3))/stamp.$(4): CFG_COMPILER_HOST_TRIPLE = $(2)
-$$(TLIB$(1)_T_$(2)_H_$(3))/stamp.$(4): \
-	export RUSTC_BOOTSTRAP_KEY := $$(BOOTSTRAP_KEY$(1)_T_$(2)_H_$(3))
 $$(TLIB$(1)_T_$(2)_H_$(3))/stamp.$(4): \
 		$$(CRATEFILE_$(4)) \
 		$$(CRATE_FULLDEPS_$(1)_T_$(2)_H_$(3)_$(4)) \
@@ -132,8 +113,6 @@ endef
 # $(4) - name of the tool being built
 define TARGET_TOOL
 
-$$(TBIN$(1)_T_$(2)_H_$(3))/$(4)$$(X_$(2)): \
-	export RUSTC_BOOTSTRAP_KEY := $$(BOOTSTRAP_KEY$(1)_T_$(2)_H_$(3))
 $$(TBIN$(1)_T_$(2)_H_$(3))/$(4)$$(X_$(2)): \
 		$$(TOOL_SOURCE_$(4)) \
 		$$(TOOL_INPUTS_$(4)) \
diff --git a/src/bootstrap/check.rs b/src/bootstrap/check.rs
index 2b9d717cbd48d..603a5ce752f0a 100644
--- a/src/bootstrap/check.rs
+++ b/src/bootstrap/check.rs
@@ -185,7 +185,7 @@ pub fn compiletest(build: &Build,
             }
         }
     }
-    build.add_bootstrap_key(compiler, &mut cmd);
+    build.add_bootstrap_key(&mut cmd);
 
     cmd.arg("--adb-path").arg("adb");
     cmd.arg("--adb-test-dir").arg(ADB_TEST_DIR);
diff --git a/src/bootstrap/compile.rs b/src/bootstrap/compile.rs
index 9de438cfa7d50..239db55ff5b3b 100644
--- a/src/bootstrap/compile.rs
+++ b/src/bootstrap/compile.rs
@@ -133,7 +133,7 @@ fn build_startup_objects(build: &Build, target: &str, into: &Path) {
     for file in t!(fs::read_dir(build.src.join("src/rtstartup"))) {
         let file = t!(file);
         let mut cmd = Command::new(&compiler_path);
-        build.add_bootstrap_key(&compiler, &mut cmd);
+        build.add_bootstrap_key(&mut cmd);
         build.run(cmd.arg("--target").arg(target)
                      .arg("--emit=obj")
                      .arg("--out-dir").arg(into)
@@ -199,7 +199,6 @@ pub fn rustc<'a>(build: &'a Build, target: &str, compiler: &Compiler<'a>) {
     cargo.env("CFG_RELEASE", &build.release)
          .env("CFG_RELEASE_CHANNEL", &build.config.channel)
          .env("CFG_VERSION", &build.version)
-         .env("CFG_BOOTSTRAP_KEY", &build.bootstrap_key)
          .env("CFG_PREFIX", build.config.prefix.clone().unwrap_or(String::new()))
          .env("CFG_LIBDIR_RELATIVE", "lib");
 
diff --git a/src/bootstrap/lib.rs b/src/bootstrap/lib.rs
index bcc53129f8d8e..4dea0e3f9e735 100644
--- a/src/bootstrap/lib.rs
+++ b/src/bootstrap/lib.rs
@@ -647,7 +647,7 @@ impl Build {
              .env("RUSTDOC_REAL", self.rustdoc(compiler))
              .env("RUSTC_FLAGS", self.rustc_flags(target).join(" "));
 
-        self.add_bootstrap_key(compiler, &mut cargo);
+        self.add_bootstrap_key(&mut cargo);
 
         // Specify some various options for build scripts used throughout
         // the build.
@@ -862,16 +862,11 @@ impl Build {
     }
 
     /// Adds the compiler's bootstrap key to the environment of `cmd`.
-    fn add_bootstrap_key(&self, compiler: &Compiler, cmd: &mut Command) {
-        // In stage0 we're using a previously released stable compiler, so we
-        // use the stage0 bootstrap key. Otherwise we use our own build's
-        // bootstrap key.
-        let bootstrap_key = if compiler.is_snapshot(self) && !self.local_rebuild {
-            &self.bootstrap_key_stage0
-        } else {
-            &self.bootstrap_key
-        };
-        cmd.env("RUSTC_BOOTSTRAP_KEY", bootstrap_key);
+    fn add_bootstrap_key(&self, cmd: &mut Command) {
+        cmd.env("RUSTC_BOOTSTRAP", "");
+        // FIXME: Transitionary measure to bootstrap using the old bootstrap logic.
+        // Remove this once the bootstrap compiler uses the new login in Issue #36548.
+        cmd.env("RUSTC_BOOTSTRAP_KEY", "5c6cf767");
     }
 
     /// Returns the compiler's libdir where it stores the dynamic libraries that
diff --git a/src/librustc/mir/repr.rs b/src/librustc/mir/repr.rs
index 70b0b810c6c48..c55a319d34eb9 100644
--- a/src/librustc/mir/repr.rs
+++ b/src/librustc/mir/repr.rs
@@ -1131,8 +1131,7 @@ impl<'tcx> Debug for Rvalue<'tcx> {
                     Adt(adt_def, variant, substs, _) => {
                         let variant_def = &adt_def.variants[variant];
 
-                        ppaux::parameterized(fmt, substs, variant_def.did,
-                                             ppaux::Ns::Value, &[])?;
+                        ppaux::parameterized(fmt, substs, variant_def.did, &[])?;
 
                         match variant_def.kind {
                             ty::VariantKind::Unit => Ok(()),
@@ -1227,7 +1226,7 @@ impl<'tcx> Debug for Literal<'tcx> {
         use self::Literal::*;
         match *self {
             Item { def_id, substs } => {
-                ppaux::parameterized(fmt, substs, def_id, ppaux::Ns::Value, &[])
+                ppaux::parameterized(fmt, substs, def_id, &[])
             }
             Value { ref value } => {
                 write!(fmt, "const ")?;
diff --git a/src/librustc/traits/select.rs b/src/librustc/traits/select.rs
index 9d7131dc96cc5..05b4c44580e17 100644
--- a/src/librustc/traits/select.rs
+++ b/src/librustc/traits/select.rs
@@ -336,7 +336,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
         self.infcx.tcx
     }
 
-    pub fn param_env(&self) -> &'cx ty::ParameterEnvironment<'tcx> {
+    pub fn param_env(&self) -> &'cx ty::ParameterEnvironment<'gcx> {
         self.infcx.param_env()
     }
 
diff --git a/src/librustc/traits/specialize/mod.rs b/src/librustc/traits/specialize/mod.rs
index e37425901c8c8..6a27558b0b77e 100644
--- a/src/librustc/traits/specialize/mod.rs
+++ b/src/librustc/traits/specialize/mod.rs
@@ -148,6 +148,8 @@ pub fn find_method<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 pub fn specializes<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                              impl1_def_id: DefId,
                              impl2_def_id: DefId) -> bool {
+    debug!("specializes({:?}, {:?})", impl1_def_id, impl2_def_id);
+
     if let Some(r) = tcx.specializes_cache.borrow().check(impl1_def_id, impl2_def_id) {
         return r;
     }
@@ -177,21 +179,22 @@ pub fn specializes<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     }
 
     // create a parameter environment corresponding to a (skolemized) instantiation of impl1
-    let mut penv = tcx.construct_parameter_environment(DUMMY_SP,
-                                                       impl1_def_id,
-                                                       region::DUMMY_CODE_EXTENT);
+    let penv = tcx.construct_parameter_environment(DUMMY_SP,
+                                                   impl1_def_id,
+                                                   region::DUMMY_CODE_EXTENT);
     let impl1_trait_ref = tcx.impl_trait_ref(impl1_def_id)
                              .unwrap()
                              .subst(tcx, &penv.free_substs);
 
-    let result = tcx.infer_ctxt(None, None, Reveal::ExactMatch).enter(|mut infcx| {
+    // Create a infcx, taking the predicates of impl1 as assumptions:
+    let result = tcx.infer_ctxt(None, Some(penv), Reveal::ExactMatch).enter(|mut infcx| {
         // Normalize the trait reference, adding any obligations
         // that arise into the impl1 assumptions.
         let Normalized { value: impl1_trait_ref, obligations: normalization_obligations } = {
             let selcx = &mut SelectionContext::new(&infcx);
             traits::normalize(selcx, ObligationCause::dummy(), &impl1_trait_ref)
         };
-        penv.caller_bounds.extend(normalization_obligations.into_iter().map(|o| {
+        infcx.parameter_environment.caller_bounds.extend(normalization_obligations.into_iter().map(|o| {
             match tcx.lift_to_global(&o.predicate) {
                 Some(predicate) => predicate,
                 None => {
@@ -200,9 +203,6 @@ pub fn specializes<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
             }
         }));
 
-        // Install the parameter environment, taking the predicates of impl1 as assumptions:
-        infcx.parameter_environment = penv;
-
         // Attempt to prove that impl2 applies, given all of the above.
         fulfill_implication(&infcx, impl1_trait_ref, impl2_def_id).is_ok()
     });
diff --git a/src/librustc/ty/mod.rs b/src/librustc/ty/mod.rs
index 723af1f0d90a4..d38a30ee631c8 100644
--- a/src/librustc/ty/mod.rs
+++ b/src/librustc/ty/mod.rs
@@ -34,7 +34,7 @@ use util::nodemap::FnvHashMap;
 
 use serialize::{self, Encodable, Encoder};
 use std::borrow::Cow;
-use std::cell::Cell;
+use std::cell::{Cell, RefCell};
 use std::hash::{Hash, Hasher};
 use std::iter;
 use std::ops::Deref;
@@ -1220,6 +1220,12 @@ pub struct ParameterEnvironment<'tcx> {
     /// regions don't have this implicit scope and instead introduce
     /// relationships in the environment.
     pub free_id_outlive: CodeExtent,
+
+    /// A cache for `moves_by_default`.
+    pub is_copy_cache: RefCell<FnvHashMap<Ty<'tcx>, bool>>,
+
+    /// A cache for `type_is_sized`
+    pub is_sized_cache: RefCell<FnvHashMap<Ty<'tcx>, bool>>,
 }
 
 impl<'a, 'tcx> ParameterEnvironment<'tcx> {
@@ -1232,6 +1238,8 @@ impl<'a, 'tcx> ParameterEnvironment<'tcx> {
             implicit_region_bound: self.implicit_region_bound,
             caller_bounds: caller_bounds,
             free_id_outlive: self.free_id_outlive,
+            is_copy_cache: RefCell::new(FnvHashMap()),
+            is_sized_cache: RefCell::new(FnvHashMap()),
         }
     }
 
@@ -2782,7 +2790,9 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
             free_substs: Substs::empty(self),
             caller_bounds: Vec::new(),
             implicit_region_bound: self.mk_region(ty::ReEmpty),
-            free_id_outlive: free_id_outlive
+            free_id_outlive: free_id_outlive,
+            is_copy_cache: RefCell::new(FnvHashMap()),
+            is_sized_cache: RefCell::new(FnvHashMap()),
         }
     }
 
@@ -2853,6 +2863,8 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
             implicit_region_bound: tcx.mk_region(ty::ReScope(free_id_outlive)),
             caller_bounds: predicates,
             free_id_outlive: free_id_outlive,
+            is_copy_cache: RefCell::new(FnvHashMap()),
+            is_sized_cache: RefCell::new(FnvHashMap()),
         };
 
         let cause = traits::ObligationCause::misc(span, free_id_outlive.node_id(&self.region_maps));
diff --git a/src/librustc/ty/structural_impls.rs b/src/librustc/ty/structural_impls.rs
index 5a87ea1473d98..1715185373684 100644
--- a/src/librustc/ty/structural_impls.rs
+++ b/src/librustc/ty/structural_impls.rs
@@ -908,23 +908,6 @@ impl<'tcx> TypeFoldable<'tcx> for ty::ClosureUpvar<'tcx> {
     }
 }
 
-impl<'tcx> TypeFoldable<'tcx> for ty::ParameterEnvironment<'tcx> {
-    fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, folder: &mut F) -> Self {
-        ty::ParameterEnvironment {
-            free_substs: self.free_substs.fold_with(folder),
-            implicit_region_bound: self.implicit_region_bound.fold_with(folder),
-            caller_bounds: self.caller_bounds.fold_with(folder),
-            free_id_outlive: self.free_id_outlive,
-        }
-    }
-
-    fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
-        self.free_substs.visit_with(visitor) ||
-            self.implicit_region_bound.visit_with(visitor) ||
-            self.caller_bounds.visit_with(visitor)
-    }
-}
-
 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for ty::error::ExpectedFound<T> {
     fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, folder: &mut F) -> Self {
         ty::error::ExpectedFound {
diff --git a/src/librustc/ty/util.rs b/src/librustc/ty/util.rs
index c9ab577a9921d..5b0f43e3cf1f2 100644
--- a/src/librustc/ty/util.rs
+++ b/src/librustc/ty/util.rs
@@ -20,9 +20,11 @@ use ty::{Disr, ParameterEnvironment};
 use ty::fold::TypeVisitor;
 use ty::layout::{Layout, LayoutError};
 use ty::TypeVariants::*;
+use util::nodemap::FnvHashMap;
 
 use rustc_const_math::{ConstInt, ConstIsize, ConstUsize};
 
+use std::cell::RefCell;
 use std::cmp;
 use std::hash::{Hash, Hasher};
 use std::collections::hash_map::DefaultHasher;
@@ -579,11 +581,24 @@ impl<'a, 'gcx, 'tcx, H: Hasher> TypeVisitor<'tcx> for TypeIdHasher<'a, 'gcx, 'tc
 impl<'a, 'tcx> ty::TyS<'tcx> {
     fn impls_bound(&'tcx self, tcx: TyCtxt<'a, 'tcx, 'tcx>,
                    param_env: &ParameterEnvironment<'tcx>,
-                   bound: ty::BuiltinBound, span: Span) -> bool
+                   bound: ty::BuiltinBound,
+                   cache: &RefCell<FnvHashMap<Ty<'tcx>, bool>>,
+                   span: Span) -> bool
     {
-        tcx.infer_ctxt(None, Some(param_env.clone()), Reveal::ExactMatch).enter(|infcx| {
-            traits::type_known_to_meet_builtin_bound(&infcx, self, bound, span)
-        })
+        if self.has_param_types() || self.has_self_ty() {
+            if let Some(result) = cache.borrow().get(self) {
+                return *result;
+            }
+        }
+        let result =
+            tcx.infer_ctxt(None, Some(param_env.clone()), Reveal::ExactMatch)
+            .enter(|infcx| {
+                traits::type_known_to_meet_builtin_bound(&infcx, self, bound, span)
+            });
+        if self.has_param_types() || self.has_self_ty() {
+            cache.borrow_mut().insert(self, result);
+        }
+        return result;
     }
 
     // FIXME (@jroesch): I made this public to use it, not sure if should be private
@@ -610,7 +625,9 @@ impl<'a, 'tcx> ty::TyS<'tcx> {
             TyArray(..) | TySlice(..) | TyTrait(..) | TyTuple(..) |
             TyClosure(..) | TyAdt(..) | TyAnon(..) |
             TyProjection(..) | TyParam(..) | TyInfer(..) | TyError => None
-        }.unwrap_or_else(|| !self.impls_bound(tcx, param_env, ty::BoundCopy, span));
+        }.unwrap_or_else(|| {
+            !self.impls_bound(tcx, param_env, ty::BoundCopy, &param_env.is_copy_cache, span)
+        });
 
         if !self.has_param_types() && !self.has_self_ty() {
             self.flags.set(self.flags.get() | if result {
@@ -650,7 +667,9 @@ impl<'a, 'tcx> ty::TyS<'tcx> {
 
             TyAdt(..) | TyProjection(..) | TyParam(..) |
             TyInfer(..) | TyAnon(..) | TyError => None
-        }.unwrap_or_else(|| self.impls_bound(tcx, param_env, ty::BoundSized, span));
+        }.unwrap_or_else(|| {
+            self.impls_bound(tcx, param_env, ty::BoundSized, &param_env.is_sized_cache, span)
+        });
 
         if !self.has_param_types() && !self.has_self_ty() {
             self.flags.set(self.flags.get() | if result {
diff --git a/src/librustc/util/ppaux.rs b/src/librustc/util/ppaux.rs
index 1df0cf2d5cdf6..312cab245442a 100644
--- a/src/librustc/util/ppaux.rs
+++ b/src/librustc/util/ppaux.rs
@@ -10,6 +10,7 @@
 
 use hir::def_id::DefId;
 use ty::subst::{self, Subst, Substs};
+use hir::map::definitions::DefPathData;
 use ty::{BrAnon, BrEnv, BrFresh, BrNamed};
 use ty::{TyBool, TyChar, TyAdt};
 use ty::{TyError, TyStr, TyArray, TySlice, TyFloat, TyFnDef, TyFnPtr};
@@ -56,27 +57,55 @@ fn fn_sig(f: &mut fmt::Formatter,
     Ok(())
 }
 
-/// Namespace of the path given to parameterized to print.
-#[derive(Copy, Clone, PartialEq, Debug)]
-pub enum Ns {
-    Type,
-    Value
-}
-
 pub fn parameterized(f: &mut fmt::Formatter,
                      substs: &subst::Substs,
-                     did: DefId,
-                     ns: Ns,
+                     mut did: DefId,
                      projections: &[ty::ProjectionPredicate])
                      -> fmt::Result {
+    let key = ty::tls::with(|tcx| tcx.def_key(did));
+    let mut item_name = if let Some(name) = key.disambiguated_data.data.get_opt_name() {
+        Some(name)
+    } else {
+        did.index = key.parent.unwrap_or_else(
+            || bug!("finding type for {:?}, encountered def-id {:?} with no parent",
+                    did, did));
+        parameterized(f, substs, did, projections)?;
+        return write!(f, "::{}", key.disambiguated_data.data.as_interned_str());
+    };
+
     let mut verbose = false;
     let mut num_supplied_defaults = 0;
     let mut has_self = false;
     let mut num_regions = 0;
     let mut num_types = 0;
-    let mut item_name = None;
+    let mut is_value_path = false;
     let fn_trait_kind = ty::tls::with(|tcx| {
-        let mut generics = tcx.lookup_generics(did);
+        // Unfortunately, some kinds of items (e.g., closures) don't have
+        // generics. So walk back up the find the closest parent that DOES
+        // have them.
+        let mut item_def_id = did;
+        loop {
+            let key = tcx.def_key(item_def_id);
+            match key.disambiguated_data.data {
+                DefPathData::TypeNs(_) => {
+                    break;
+                }
+                DefPathData::ValueNs(_) | DefPathData::EnumVariant(_) => {
+                    is_value_path = true;
+                    break;
+                }
+                _ => {
+                    // if we're making a symbol for something, there ought
+                    // to be a value or type-def or something in there
+                    // *somewhere*
+                    item_def_id.index = key.parent.unwrap_or_else(|| {
+                        bug!("finding type for {:?}, encountered def-id {:?} with no \
+                             parent", did, item_def_id);
+                    });
+                }
+            }
+        }
+        let mut generics = tcx.lookup_generics(item_def_id);
         let mut path_def_id = did;
         verbose = tcx.sess.verbose();
         has_self = generics.has_self;
@@ -84,7 +113,7 @@ pub fn parameterized(f: &mut fmt::Formatter,
         let mut child_types = 0;
         if let Some(def_id) = generics.parent {
             // Methods.
-            assert_eq!(ns, Ns::Value);
+            assert!(is_value_path);
             child_types = generics.types.len();
             generics = tcx.lookup_generics(def_id);
             num_regions = generics.regions.len();
@@ -94,10 +123,11 @@ pub fn parameterized(f: &mut fmt::Formatter,
                 write!(f, "<{} as ", substs.type_at(0))?;
             }
 
-            item_name = Some(tcx.item_name(did));
             path_def_id = def_id;
         } else {
-            if ns == Ns::Value {
+            item_name = None;
+
+            if is_value_path {
                 // Functions.
                 assert_eq!(has_self, false);
             } else {
@@ -192,7 +222,7 @@ pub fn parameterized(f: &mut fmt::Formatter,
     start_or_continue(f, "", ">")?;
 
     // For values, also print their name and type parameters.
-    if ns == Ns::Value {
+    if is_value_path {
         empty.set(true);
 
         if has_self {
@@ -298,7 +328,6 @@ impl<'tcx> fmt::Display for TraitAndProjections<'tcx> {
         let TraitAndProjections(ref trait_ref, ref projection_bounds) = *self;
         parameterized(f, trait_ref.substs,
                       trait_ref.def_id,
-                      Ns::Type,
                       projection_bounds)
     }
 }
@@ -398,7 +427,7 @@ impl<'tcx> fmt::Debug for ty::ExistentialTraitRef<'tcx> {
             let trait_ref = tcx.lift(&ty::Binder(*self))
                                .expect("could not lift TraitRef for printing")
                                .with_self_ty(tcx, dummy_self).0;
-            parameterized(f, trait_ref.substs, trait_ref.def_id, Ns::Type, &[])
+            parameterized(f, trait_ref.substs, trait_ref.def_id, &[])
         })
     }
 }
@@ -798,7 +827,7 @@ impl<'tcx> fmt::Display for ty::Binder<ty::OutlivesPredicate<&'tcx ty::Region,
 
 impl<'tcx> fmt::Display for ty::TraitRef<'tcx> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        parameterized(f, self.substs, self.def_id, Ns::Type, &[])
+        parameterized(f, self.substs, self.def_id, &[])
     }
 }
 
@@ -851,7 +880,7 @@ impl<'tcx> fmt::Display for ty::TypeVariants<'tcx> {
                 }
 
                 write!(f, "{} {{", bare_fn.sig.0)?;
-                parameterized(f, substs, def_id, Ns::Value, &[])?;
+                parameterized(f, substs, def_id, &[])?;
                 write!(f, "}}")
             }
             TyFnPtr(ref bare_fn) => {
@@ -874,7 +903,7 @@ impl<'tcx> fmt::Display for ty::TypeVariants<'tcx> {
                           !tcx.tcache.borrow().contains_key(&def.did) {
                         write!(f, "{}<..>", tcx.item_path_str(def.did))
                     } else {
-                        parameterized(f, substs, def.did, Ns::Type, &[])
+                        parameterized(f, substs, def.did, &[])
                     }
                 })
             }
diff --git a/src/librustc_metadata/decoder.rs b/src/librustc_metadata/decoder.rs
index 3e4a2542b270b..ceb6fcb0da8c2 100644
--- a/src/librustc_metadata/decoder.rs
+++ b/src/librustc_metadata/decoder.rs
@@ -1106,6 +1106,10 @@ impl<'a, 'tcx> CrateMetadata {
 }
 
 fn are_equal_modulo_startpos(fm1: &syntax_pos::FileMap, fm2: &syntax_pos::FileMap) -> bool {
+    if fm1.byte_length() != fm2.byte_length() {
+        return false;
+    }
+
     if fm1.name != fm2.name {
         return false;
     }
diff --git a/src/librustc_resolve/lib.rs b/src/librustc_resolve/lib.rs
index 38b31db678143..798614ce58196 100644
--- a/src/librustc_resolve/lib.rs
+++ b/src/librustc_resolve/lib.rs
@@ -56,7 +56,7 @@ use rustc::util::nodemap::{NodeMap, NodeSet, FnvHashMap, FnvHashSet};
 use syntax::ext::base::MultiItemModifier;
 use syntax::ext::hygiene::Mark;
 use syntax::ast::{self, FloatTy};
-use syntax::ast::{CRATE_NODE_ID, Name, NodeId, IntTy, UintTy};
+use syntax::ast::{CRATE_NODE_ID, Name, NodeId, SpannedIdent, IntTy, UintTy};
 use syntax::parse::token::{self, keywords};
 use syntax::util::lev_distance::find_best_match_for_name;
 
@@ -2237,7 +2237,7 @@ impl<'a> Resolver<'a> {
     }
 
     fn fresh_binding(&mut self,
-                     ident: &ast::SpannedIdent,
+                     ident: &SpannedIdent,
                      pat_id: NodeId,
                      outer_pat_id: NodeId,
                      pat_src: PatternSource,
@@ -2803,11 +2803,11 @@ impl<'a> Resolver<'a> {
         } SuggestionType::NotFound
     }
 
-    fn resolve_labeled_block(&mut self, label: Option<ast::Ident>, id: NodeId, block: &Block) {
+    fn resolve_labeled_block(&mut self, label: Option<SpannedIdent>, id: NodeId, block: &Block) {
         if let Some(label) = label {
             let def = Def::Label(id);
             self.with_label_rib(|this| {
-                this.label_ribs.last_mut().unwrap().bindings.insert(label, def);
+                this.label_ribs.last_mut().unwrap().bindings.insert(label.node, def);
                 this.visit_block(block);
             });
         } else {
@@ -3006,19 +3006,6 @@ impl<'a> Resolver<'a> {
                 visit::walk_expr(self, expr);
             }
 
-            ExprKind::Loop(_, Some(label)) | ExprKind::While(.., Some(label)) => {
-                self.with_label_rib(|this| {
-                    let def = Def::Label(expr.id);
-
-                    {
-                        let rib = this.label_ribs.last_mut().unwrap();
-                        rib.bindings.insert(label.node, def);
-                    }
-
-                    visit::walk_expr(this, expr);
-                })
-            }
-
             ExprKind::Break(Some(label)) | ExprKind::Continue(Some(label)) => {
                 match self.search_label(label.node) {
                     None => {
@@ -3048,12 +3035,19 @@ impl<'a> Resolver<'a> {
                 optional_else.as_ref().map(|expr| self.visit_expr(expr));
             }
 
+            ExprKind::Loop(ref block, label) => self.resolve_labeled_block(label, expr.id, &block),
+
+            ExprKind::While(ref subexpression, ref block, label) => {
+                self.visit_expr(subexpression);
+                self.resolve_labeled_block(label, expr.id, &block);
+            }
+
             ExprKind::WhileLet(ref pattern, ref subexpression, ref block, label) => {
                 self.visit_expr(subexpression);
                 self.value_ribs.push(Rib::new(NormalRibKind));
                 self.resolve_pattern(pattern, PatternSource::WhileLet, &mut FnvHashMap());
 
-                self.resolve_labeled_block(label.map(|l| l.node), expr.id, block);
+                self.resolve_labeled_block(label, expr.id, block);
 
                 self.value_ribs.pop();
             }
@@ -3063,7 +3057,7 @@ impl<'a> Resolver<'a> {
                 self.value_ribs.push(Rib::new(NormalRibKind));
                 self.resolve_pattern(pattern, PatternSource::For, &mut FnvHashMap());
 
-                self.resolve_labeled_block(label.map(|l| l.node), expr.id, block);
+                self.resolve_labeled_block(label, expr.id, block);
 
                 self.value_ribs.pop();
             }
diff --git a/src/librustc_trans/monomorphize.rs b/src/librustc_trans/monomorphize.rs
index ab2a39864336f..270ce79620f8b 100644
--- a/src/librustc_trans/monomorphize.rs
+++ b/src/librustc_trans/monomorphize.rs
@@ -26,7 +26,7 @@ pub struct Instance<'tcx> {
 
 impl<'tcx> fmt::Display for Instance<'tcx> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        ppaux::parameterized(f, &self.substs, self.def, ppaux::Ns::Value, &[])
+        ppaux::parameterized(f, &self.substs, self.def, &[])
     }
 }
 
diff --git a/src/librustc_typeck/check/mod.rs b/src/librustc_typeck/check/mod.rs
index ee00cb2f5a3e4..81518496132ed 100644
--- a/src/librustc_typeck/check/mod.rs
+++ b/src/librustc_typeck/check/mod.rs
@@ -1458,7 +1458,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
         }
     }
 
-    pub fn param_env(&self) -> &ty::ParameterEnvironment<'tcx> {
+    pub fn param_env(&self) -> &ty::ParameterEnvironment<'gcx> {
         &self.parameter_environment
     }
 
diff --git a/src/libsyntax/feature_gate.rs b/src/libsyntax/feature_gate.rs
index e37deaa60f219..2f4aa2e58e2f1 100644
--- a/src/libsyntax/feature_gate.rs
+++ b/src/libsyntax/feature_gate.rs
@@ -1296,15 +1296,12 @@ impl UnstableFeatures {
     pub fn from_environment() -> UnstableFeatures {
         // Whether this is a feature-staged build, i.e. on the beta or stable channel
         let disable_unstable_features = option_env!("CFG_DISABLE_UNSTABLE_FEATURES").is_some();
-        // The secret key needed to get through the rustc build itself by
-        // subverting the unstable features lints
-        let bootstrap_secret_key = option_env!("CFG_BOOTSTRAP_KEY");
-        // The matching key to the above, only known by the build system
-        let bootstrap_provided_key = env::var("RUSTC_BOOTSTRAP_KEY").ok();
-        match (disable_unstable_features, bootstrap_secret_key, bootstrap_provided_key) {
-            (_, Some(ref s), Some(ref p)) if s == p => UnstableFeatures::Cheat,
-            (true, _, _) => UnstableFeatures::Disallow,
-            (false, _, _) => UnstableFeatures::Allow
+        // Whether we should enable unstable features for bootstrapping
+        let bootstrap = env::var("RUSTC_BOOTSTRAP").is_ok();
+        match (disable_unstable_features, bootstrap) {
+            (_, true) => UnstableFeatures::Cheat,
+            (true, _) => UnstableFeatures::Disallow,
+            (false, _) => UnstableFeatures::Allow
         }
     }
 
diff --git a/src/libsyntax_pos/lib.rs b/src/libsyntax_pos/lib.rs
index e3feaee5369d1..d83d3a6c5cfac 100644
--- a/src/libsyntax_pos/lib.rs
+++ b/src/libsyntax_pos/lib.rs
@@ -481,6 +481,9 @@ impl FileMap {
         self.src.is_none()
     }
 
+    pub fn byte_length(&self) -> u32 {
+        self.end_pos.0 - self.start_pos.0
+    }
     pub fn count_lines(&self) -> usize {
         self.lines.borrow().len()
     }
diff --git a/src/stage0.txt b/src/stage0.txt
index 0f097ac766fd5..bfab0211b3b00 100644
--- a/src/stage0.txt
+++ b/src/stage0.txt
@@ -13,5 +13,4 @@
 # released on `$date`
 
 rustc: 1.12.1-2016-10-20
-rustc_key: 5c6cf767
 cargo: nightly-2016-08-21
diff --git a/src/test/compile-fail/resolve-label.rs b/src/test/compile-fail/resolve-label.rs
index 398b4f5859e65..ed2c3e0e9b860 100644
--- a/src/test/compile-fail/resolve-label.rs
+++ b/src/test/compile-fail/resolve-label.rs
@@ -16,6 +16,9 @@ fn f() {
             }
         }
     }
+
+    // issue #37353
+    loop { 'w: while break 'w { } } //~ ERROR use of undeclared label
 }
 
 fn main() {}
diff --git a/src/test/run-pass/issue-37291/auxiliary/lib.rs b/src/test/run-pass/issue-37291/auxiliary/lib.rs
new file mode 100644
index 0000000000000..67cdea807beeb
--- /dev/null
+++ b/src/test/run-pass/issue-37291/auxiliary/lib.rs
@@ -0,0 +1,52 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![crate_type = "lib"]
+
+use std::ops::Mul;
+
+pub trait A {}
+pub trait B {
+    type AT: A;
+}
+pub trait C {
+    type BT: B;
+}
+
+pub struct AV;
+impl A for AV {}
+
+pub struct BV;
+impl B for BV {
+    type AT = AV;
+}
+
+pub struct CV;
+impl C for CV {
+    type BT = BV;
+}
+
+pub struct WrapperB<T>(pub T);
+pub struct WrapperC<T>(pub T);
+
+impl<C1> Mul<WrapperB<<C1::BT as B>::AT>> for WrapperC<C1>
+    where C1: C
+{
+    type Output = u8;
+    fn mul(self, _: WrapperB<<C1::BT as B>::AT>) -> Self::Output {
+        loop {}
+    }
+}
+impl<C1> Mul<WrapperC<C1>> for WrapperC<C1> {
+    type Output = u8;
+    fn mul(self, _: WrapperC<C1>) -> Self::Output {
+        loop {}
+    }
+}
diff --git a/src/test/run-pass/issue-37291/main.rs b/src/test/run-pass/issue-37291/main.rs
new file mode 100644
index 0000000000000..2461f7485f26f
--- /dev/null
+++ b/src/test/run-pass/issue-37291/main.rs
@@ -0,0 +1,29 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// aux-build:lib.rs
+
+// Regression test for #37291. The problem was that the starting
+// environment for a specialization check was not including the
+// where-clauses from the impl when attempting to normalize the impl's
+// trait-ref, so things like `<C as Foo>::Item` could not resolve,
+// since the `C: Foo` trait bound was not included in the environment.
+
+extern crate lib;
+
+use lib::{CV, WrapperB, WrapperC};
+
+fn main() {
+    let a = WrapperC(CV);
+    let b = WrapperC(CV);
+    if false {
+        let _ = a * b;
+    }
+}