diff --git a/compiler/rustc_metadata/src/rmeta/decoder.rs b/compiler/rustc_metadata/src/rmeta/decoder.rs
index 8ff3b1e72d8..71943ba2dc9 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder.rs
@@ -27,6 +27,7 @@ use rustc_middle::mir::interpret::{AllocDecodingSession, AllocDecodingState};
 use rustc_middle::mir::{self, Body, Promoted};
 use rustc_middle::thir;
 use rustc_middle::ty::codec::TyDecoder;
+use rustc_middle::ty::fast_reject::SimplifiedType;
 use rustc_middle::ty::{self, Ty, TyCtxt, Visibility};
 use rustc_serialize::{opaque, Decodable, Decoder};
 use rustc_session::cstore::{
@@ -92,8 +93,7 @@ crate struct CrateMetadata {
     /// Trait impl data.
     /// FIXME: Used only from queries and can use query cache,
     /// so pre-decoding can probably be avoided.
-    trait_impls:
-        FxHashMap<(u32, DefIndex), Lazy<[(DefIndex, Option<ty::fast_reject::SimplifiedType>)]>>,
+    trait_impls: FxHashMap<(u32, DefIndex), Lazy<[(DefIndex, Option<SimplifiedType>)]>>,
     /// Proc macro descriptions for this crate, if it's a proc macro crate.
     raw_proc_macros: Option<&'static [ProcMacro]>,
     /// Source maps for code from the crate.
@@ -1376,7 +1376,7 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
         &self,
         tcx: TyCtxt<'tcx>,
         filter: Option<DefId>,
-    ) -> &'tcx [(DefId, Option<ty::fast_reject::SimplifiedType>)] {
+    ) -> &'tcx [(DefId, Option<SimplifiedType>)] {
         if self.root.is_proc_macro_crate() {
             // proc-macro crates export no trait impls.
             return &[];
diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs
index 3942846e79d..12d66f4fc45 100644
--- a/compiler/rustc_metadata/src/rmeta/encoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/encoder.rs
@@ -26,7 +26,7 @@ use rustc_middle::mir::interpret;
 use rustc_middle::thir;
 use rustc_middle::traits::specialization_graph;
 use rustc_middle::ty::codec::TyEncoder;
-use rustc_middle::ty::fast_reject::{self, SimplifyParams, StripReferences};
+use rustc_middle::ty::fast_reject::{self, SimplifiedType, SimplifyParams, StripReferences};
 use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::{self, SymbolName, Ty, TyCtxt};
 use rustc_serialize::{opaque, Encodable, Encoder};
@@ -2055,7 +2055,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
 
 struct ImplsVisitor<'tcx> {
     tcx: TyCtxt<'tcx>,
-    impls: FxHashMap<DefId, Vec<(DefIndex, Option<fast_reject::SimplifiedType>)>>,
+    impls: FxHashMap<DefId, Vec<(DefIndex, Option<SimplifiedType>)>>,
 }
 
 impl<'tcx, 'v> ItemLikeVisitor<'v> for ImplsVisitor<'tcx> {
diff --git a/compiler/rustc_metadata/src/rmeta/mod.rs b/compiler/rustc_metadata/src/rmeta/mod.rs
index 35016453369..4076e0b9e0f 100644
--- a/compiler/rustc_metadata/src/rmeta/mod.rs
+++ b/compiler/rustc_metadata/src/rmeta/mod.rs
@@ -16,6 +16,7 @@ use rustc_middle::hir::exports::Export;
 use rustc_middle::middle::exported_symbols::{ExportedSymbol, SymbolExportLevel};
 use rustc_middle::mir;
 use rustc_middle::thir;
+use rustc_middle::ty::fast_reject::SimplifiedType;
 use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::{self, ReprOptions, Ty};
 use rustc_serialize::opaque::Encoder;
@@ -261,7 +262,7 @@ crate struct CrateDep {
 #[derive(MetadataEncodable, MetadataDecodable)]
 crate struct TraitImpls {
     trait_id: (u32, DefIndex),
-    impls: Lazy<[(DefIndex, Option<ty::fast_reject::SimplifiedType>)]>,
+    impls: Lazy<[(DefIndex, Option<SimplifiedType>)]>,
 }
 
 /// Define `LazyTables` and `TableBuilders` at the same time.
diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index 027c0c64924..b3db2e63400 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -1411,16 +1411,14 @@ rustc_queries! {
 
     /// Given a crate and a trait, look up all impls of that trait in the crate.
     /// Return `(impl_id, self_ty)`.
-    query implementations_of_trait(_: (CrateNum, DefId))
-        -> &'tcx [(DefId, Option<ty::fast_reject::SimplifiedType>)] {
+    query implementations_of_trait(_: (CrateNum, DefId)) -> &'tcx [(DefId, Option<SimplifiedType>)] {
         desc { "looking up implementations of a trait in a crate" }
         separate_provide_extern
     }
 
     /// Given a crate, look up all trait impls in that crate.
     /// Return `(impl_id, self_ty)`.
-    query all_trait_implementations(_: CrateNum)
-        -> &'tcx [(DefId, Option<ty::fast_reject::SimplifiedType>)] {
+    query all_trait_implementations(_: CrateNum) -> &'tcx [(DefId, Option<SimplifiedType>)] {
         desc { "looking up all (?) trait implementations" }
         separate_provide_extern
     }
diff --git a/compiler/rustc_middle/src/ty/fast_reject.rs b/compiler/rustc_middle/src/ty/fast_reject.rs
index 04011552e31..daf9156a15f 100644
--- a/compiler/rustc_middle/src/ty/fast_reject.rs
+++ b/compiler/rustc_middle/src/ty/fast_reject.rs
@@ -143,6 +143,18 @@ pub fn simplify_type(
 }
 
 impl<D: Copy + Debug + Ord + Eq> SimplifiedTypeGen<D> {
+    pub fn def(self) -> Option<D> {
+        match self {
+            AdtSimplifiedType(d)
+            | ForeignSimplifiedType(d)
+            | TraitSimplifiedType(d)
+            | ClosureSimplifiedType(d)
+            | GeneratorSimplifiedType(d)
+            | OpaqueSimplifiedType(d) => Some(d),
+            _ => None,
+        }
+    }
+
     pub fn map_def<U, F>(self, map: F) -> SimplifiedTypeGen<U>
     where
         F: Fn(D) -> U,
diff --git a/compiler/rustc_middle/src/ty/query.rs b/compiler/rustc_middle/src/ty/query.rs
index 2f91503afdf..3af1b3a0440 100644
--- a/compiler/rustc_middle/src/ty/query.rs
+++ b/compiler/rustc_middle/src/ty/query.rs
@@ -28,6 +28,7 @@ use crate::traits::query::{
 };
 use crate::traits::specialization_graph;
 use crate::traits::{self, ImplSource};
+use crate::ty::fast_reject::SimplifiedType;
 use crate::ty::subst::{GenericArg, SubstsRef};
 use crate::ty::util::AlwaysRequiresDrop;
 use crate::ty::{self, AdtSizedConstraint, CrateInherentImpls, ParamEnvAnd, Ty, TyCtxt};
diff --git a/compiler/rustc_middle/src/ty/trait_def.rs b/compiler/rustc_middle/src/ty/trait_def.rs
index cbb88def7e2..34d059f4ec8 100644
--- a/compiler/rustc_middle/src/ty/trait_def.rs
+++ b/compiler/rustc_middle/src/ty/trait_def.rs
@@ -1,5 +1,5 @@
 use crate::traits::specialization_graph;
-use crate::ty::fast_reject::{self, SimplifyParams, StripReferences};
+use crate::ty::fast_reject::{self, SimplifiedType, SimplifyParams, StripReferences};
 use crate::ty::fold::TypeFoldable;
 use crate::ty::{Ty, TyCtxt};
 use rustc_hir as hir;
@@ -68,7 +68,7 @@ pub enum TraitSpecializationKind {
 pub struct TraitImpls {
     blanket_impls: Vec<DefId>,
     /// Impls indexed by their simplified self type, for fast lookup.
-    non_blanket_impls: FxIndexMap<fast_reject::SimplifiedType, Vec<DefId>>,
+    non_blanket_impls: FxIndexMap<SimplifiedType, Vec<DefId>>,
 }
 
 impl TraitImpls {