Create a visitor for `TypeFoldable`s and use it to implement RegionEscape and HasTypeFlags (fixes #20298)

19 files changed, 534 insertions, 690 deletions

diff --git a/src/librustc/middle/implicator.rs b/src/librustc/middle/implicator.rs
index 9f33c4df03d..a16e1c48330 100644
--- a/src/librustc/middle/implicator.rs
+++ b/src/librustc/middle/implicator.rs
@@ -404,7 +404,7 @@ impl<'a, 'tcx> Implicator<'a, 'tcx> {
     }
 
     fn fully_normalize<T>(&self, value: &T) -> Result<T,ErrorReported>
-        where T : TypeFoldable<'tcx> + ty::HasTypeFlags
+        where T : TypeFoldable<'tcx>
     {
         let value =
             traits::fully_normalize(self.infcx,
diff --git a/src/librustc/middle/infer/combine.rs b/src/librustc/middle/infer/combine.rs
index 2a25ed2c6e1..a526586802c 100644
--- a/src/librustc/middle/infer/combine.rs
+++ b/src/librustc/middle/infer/combine.rs
@@ -318,7 +318,7 @@ impl<'cx, 'tcx> ty::fold::TypeFolder<'tcx> for Generalizer<'cx, 'tcx> {
                 }
             }
             _ => {
-                ty::fold::super_fold_ty(self, t)
+                t.fold_subitems_with(self)
             }
         }
     }
diff --git a/src/librustc/middle/infer/freshen.rs b/src/librustc/middle/infer/freshen.rs
index 0bae3cd2d86..7202c0a8052 100644
--- a/src/librustc/middle/infer/freshen.rs
+++ b/src/librustc/middle/infer/freshen.rs
@@ -169,7 +169,7 @@ impl<'a, 'tcx> TypeFolder<'tcx> for TypeFreshener<'a, 'tcx> {
             ty::TyTuple(..) |
             ty::TyProjection(..) |
             ty::TyParam(..) => {
-                ty::fold::super_fold_ty(self, t)
+                t.fold_subitems_with(self)
             }
         }
     }
diff --git a/src/librustc/middle/infer/mod.rs b/src/librustc/middle/infer/mod.rs
index 21a1ee37b7f..941fb05c3d0 100644
--- a/src/librustc/middle/infer/mod.rs
+++ b/src/librustc/middle/infer/mod.rs
@@ -512,7 +512,7 @@ pub struct CombinedSnapshot {
 }
 
 pub fn normalize_associated_type<'tcx,T>(tcx: &ty::ctxt<'tcx>, value: &T) -> T
-    where T : TypeFoldable<'tcx> + HasTypeFlags
+    where T : TypeFoldable<'tcx>
 {
     debug!("normalize_associated_type(t={:?})", value);
 
@@ -546,7 +546,7 @@ pub fn drain_fulfillment_cx_or_panic<'a,'tcx,T>(span: Span,
                                                 fulfill_cx: &mut traits::FulfillmentContext<'tcx>,
                                                 result: &T)
                                                 -> T
-    where T : TypeFoldable<'tcx> + HasTypeFlags
+    where T : TypeFoldable<'tcx>
 {
     match drain_fulfillment_cx(infcx, fulfill_cx, result) {
         Ok(v) => v,
@@ -570,7 +570,7 @@ pub fn drain_fulfillment_cx<'a,'tcx,T>(infcx: &InferCtxt<'a,'tcx>,
                                        fulfill_cx: &mut traits::FulfillmentContext<'tcx>,
                                        result: &T)
                                        -> Result<T,Vec<traits::FulfillmentError<'tcx>>>
-    where T : TypeFoldable<'tcx> + HasTypeFlags
+    where T : TypeFoldable<'tcx>
 {
     debug!("drain_fulfillment_cx(result={:?})",
            result);
@@ -929,7 +929,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                          snapshot: &CombinedSnapshot,
                          value: &T)
                          -> T
-        where T : TypeFoldable<'tcx> + HasTypeFlags
+        where T : TypeFoldable<'tcx>
     {
         /*! See `higher_ranked::plug_leaks` */
 
@@ -1201,7 +1201,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
     }
 
     pub fn resolve_type_vars_if_possible<T>(&self, value: &T) -> T
-        where T: TypeFoldable<'tcx> + HasTypeFlags
+        where T: TypeFoldable<'tcx>
     {
         /*!
          * Where possible, replaces type/int/float variables in
diff --git a/src/librustc/middle/infer/resolve.rs b/src/librustc/middle/infer/resolve.rs
index 5190c658194..d89036faef9 100644
--- a/src/librustc/middle/infer/resolve.rs
+++ b/src/librustc/middle/infer/resolve.rs
@@ -40,7 +40,7 @@ impl<'a, 'tcx> ty::fold::TypeFolder<'tcx> for OpportunisticTypeResolver<'a, 'tcx
             t // micro-optimize -- if there is nothing in this type that this fold affects...
         } else {
             let t0 = self.infcx.shallow_resolve(t);
-            ty::fold::super_fold_ty(self, t0)
+            t0.fold_subitems_with(self)
         }
     }
 }
@@ -68,7 +68,7 @@ impl<'a, 'tcx> ty::fold::TypeFolder<'tcx> for OpportunisticTypeAndRegionResolver
             t // micro-optimize -- if there is nothing in this type that this fold affects...
         } else {
             let t0 = self.infcx.shallow_resolve(t);
-            ty::fold::super_fold_ty(self, t0)
+            t0.fold_subitems_with(self)
         }
     }
 
@@ -133,7 +133,7 @@ impl<'a, 'tcx> ty::fold::TypeFolder<'tcx> for FullTypeResolver<'a, 'tcx> {
                                 t));
                 }
                 _ => {
-                    ty::fold::super_fold_ty(self, t)
+                    t.fold_subitems_with(self)
                 }
             }
         }
diff --git a/src/librustc/middle/subst.rs b/src/librustc/middle/subst.rs
index aa47b32dc3e..d935b51813a 100644
--- a/src/librustc/middle/subst.rs
+++ b/src/librustc/middle/subst.rs
@@ -674,7 +674,7 @@ impl<'a, 'tcx> TypeFolder<'tcx> for SubstFolder<'a, 'tcx> {
                 self.ty_for_param(p, t)
             }
             _ => {
-                ty::fold::super_fold_ty(self, t)
+                t.fold_subitems_with(self)
             }
         };
 
diff --git a/src/librustc/middle/traits/error_reporting.rs b/src/librustc/middle/traits/error_reporting.rs
index 038c414662a..464b4dfb83b 100644
--- a/src/librustc/middle/traits/error_reporting.rs
+++ b/src/librustc/middle/traits/error_reporting.rs
@@ -185,7 +185,7 @@ fn report_on_unimplemented<'a, 'tcx>(infcx: &InferCtxt<'a, 'tcx>,
 pub fn report_overflow_error<'a, 'tcx, T>(infcx: &InferCtxt<'a, 'tcx>,
                                           obligation: &Obligation<'tcx, T>)
                                           -> !
-    where T: fmt::Display + TypeFoldable<'tcx> + HasTypeFlags
+    where T: fmt::Display + TypeFoldable<'tcx>
 {
     let predicate =
         infcx.resolve_type_vars_if_possible(&obligation.predicate);
diff --git a/src/librustc/middle/traits/mod.rs b/src/librustc/middle/traits/mod.rs
index dddd6f8bc85..01c2f561235 100644
--- a/src/librustc/middle/traits/mod.rs
+++ b/src/librustc/middle/traits/mod.rs
@@ -470,7 +470,7 @@ pub fn fully_normalize<'a,'tcx,T>(infcx: &InferCtxt<'a,'tcx>,
                                   cause: ObligationCause<'tcx>,
                                   value: &T)
                                   -> Result<T, Vec<FulfillmentError<'tcx>>>
-    where T : TypeFoldable<'tcx> + HasTypeFlags
+    where T : TypeFoldable<'tcx>
 {
     debug!("normalize_param_env(value={:?})", value);
 
diff --git a/src/librustc/middle/traits/project.rs b/src/librustc/middle/traits/project.rs
index 8fbfd513c78..9c317895c36 100644
--- a/src/librustc/middle/traits/project.rs
+++ b/src/librustc/middle/traits/project.rs
@@ -202,7 +202,7 @@ pub fn normalize<'a,'b,'tcx,T>(selcx: &'a mut SelectionContext<'b,'tcx>,
                                cause: ObligationCause<'tcx>,
                                value: &T)
                                -> Normalized<'tcx, T>
-    where T : TypeFoldable<'tcx> + HasTypeFlags
+    where T : TypeFoldable<'tcx>
 {
     normalize_with_depth(selcx, cause, 0, value)
 }
@@ -213,7 +213,7 @@ pub fn normalize_with_depth<'a,'b,'tcx,T>(selcx: &'a mut SelectionContext<'b,'tc
                                           depth: usize,
                                           value: &T)
                                           -> Normalized<'tcx, T>
-    where T : TypeFoldable<'tcx> + HasTypeFlags
+    where T : TypeFoldable<'tcx>
 {
     let mut normalizer = AssociatedTypeNormalizer::new(selcx, cause, depth);
     let result = normalizer.fold(value);
@@ -245,7 +245,7 @@ impl<'a,'b,'tcx> AssociatedTypeNormalizer<'a,'b,'tcx> {
         }
     }
 
-    fn fold<T:TypeFoldable<'tcx> + HasTypeFlags>(&mut self, value: &T) -> T {
+    fn fold<T:TypeFoldable<'tcx>>(&mut self, value: &T) -> T {
         let value = self.selcx.infcx().resolve_type_vars_if_possible(value);
 
         if !value.has_projection_types() {
@@ -273,7 +273,7 @@ impl<'a,'b,'tcx> TypeFolder<'tcx> for AssociatedTypeNormalizer<'a,'b,'tcx> {
         // normalize it when we instantiate those bound regions (which
         // should occur eventually).
 
-        let ty = ty::fold::super_fold_ty(self, ty);
+        let ty = ty.fold_subitems_with(self);
         match ty.sty {
             ty::TyProjection(ref data) if !data.has_escaping_regions() => { // (*)
 
diff --git a/src/librustc/middle/traits/select.rs b/src/librustc/middle/traits/select.rs
index bd92f974866..a31fccbb3f7 100644
--- a/src/librustc/middle/traits/select.rs
+++ b/src/librustc/middle/traits/select.rs
@@ -965,7 +965,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         match *candidate {
             Ok(Some(_)) | Err(_) => true,
             Ok(None) => {
-                cache_fresh_trait_pred.0.input_types().has_infer_types()
+                cache_fresh_trait_pred.0.trait_ref.substs.types.has_infer_types()
             }
         }
     }
diff --git a/src/librustc/middle/traits/structural_impls.rs b/src/librustc/middle/traits/structural_impls.rs
index 8ce21112001..ea165718065 100644
--- a/src/librustc/middle/traits/structural_impls.rs
+++ b/src/librustc/middle/traits/structural_impls.rs
@@ -10,8 +10,7 @@
 
 use middle::traits;
 use middle::traits::project::Normalized;
-use middle::ty::{HasTypeFlags, TypeFlags, RegionEscape};
-use middle::ty::fold::{TypeFoldable, TypeFolder};
+use middle::ty::fold::{TypeFoldable, TypeFolder, TypeVisitor};
 
 use std::fmt;
 
@@ -131,71 +130,6 @@ impl<'tcx> fmt::Debug for traits::MismatchedProjectionTypes<'tcx> {
     }
 }
 
-impl<'tcx, P: RegionEscape> RegionEscape for traits::Obligation<'tcx,P> {
-    fn has_regions_escaping_depth(&self, depth: u32) -> bool {
-        self.predicate.has_regions_escaping_depth(depth)
-    }
-}
-
-impl<'tcx, T: HasTypeFlags> HasTypeFlags for traits::Obligation<'tcx, T> {
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        self.predicate.has_type_flags(flags)
-    }
-}
-
-impl<'tcx, T: HasTypeFlags> HasTypeFlags for Normalized<'tcx, T> {
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        self.value.has_type_flags(flags) ||
-            self.obligations.has_type_flags(flags)
-    }
-}
-
-impl<'tcx, N: HasTypeFlags> HasTypeFlags for traits::VtableImplData<'tcx, N> {
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        self.substs.has_type_flags(flags) ||
-            self.nested.has_type_flags(flags)
-    }
-}
-
-impl<'tcx, N: HasTypeFlags> HasTypeFlags for traits::VtableClosureData<'tcx, N> {
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        self.substs.has_type_flags(flags) ||
-            self.nested.has_type_flags(flags)
-    }
-}
-
-impl<'tcx, N: HasTypeFlags> HasTypeFlags for traits::VtableDefaultImplData<N> {
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        self.nested.has_type_flags(flags)
-    }
-}
-
-impl<'tcx, N: HasTypeFlags> HasTypeFlags for traits::VtableBuiltinData<N> {
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        self.nested.has_type_flags(flags)
-    }
-}
-
-impl<'tcx> HasTypeFlags for traits::VtableObjectData<'tcx> {
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        self.upcast_trait_ref.has_type_flags(flags)
-    }
-}
-
-impl<'tcx, N: HasTypeFlags> HasTypeFlags for traits::Vtable<'tcx, N> {
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        match *self {
-            traits::VtableImpl(ref v) => v.has_type_flags(flags),
-            traits::VtableDefaultImpl(ref t) => t.has_type_flags(flags),
-            traits::VtableClosure(ref d) => d.has_type_flags(flags),
-            traits::VtableFnPointer(ref d) => d.has_type_flags(flags),
-            traits::VtableParam(ref n) => n.has_type_flags(flags),
-            traits::VtableBuiltin(ref d) => d.has_type_flags(flags),
-            traits::VtableObject(ref d) => d.has_type_flags(flags)
-        }
-    }
-}
-
 impl<'tcx, O: TypeFoldable<'tcx>> TypeFoldable<'tcx> for traits::Obligation<'tcx, O>
 {
     fn fold_with<F:TypeFolder<'tcx>>(&self, folder: &mut F) -> traits::Obligation<'tcx, O> {
@@ -205,6 +139,10 @@ impl<'tcx, O: TypeFoldable<'tcx>> TypeFoldable<'tcx> for traits::Obligation<'tcx
             predicate: self.predicate.fold_with(folder),
         }
     }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.predicate.visit_with(visitor)
+    }
 }
 
 impl<'tcx, N: TypeFoldable<'tcx>> TypeFoldable<'tcx> for traits::VtableImplData<'tcx, N> {
@@ -215,6 +153,10 @@ impl<'tcx, N: TypeFoldable<'tcx>> TypeFoldable<'tcx> for traits::VtableImplData<
             nested: self.nested.fold_with(folder),
         }
     }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.substs.visit_with(visitor) || self.nested.visit_with(visitor)
+    }
 }
 
 impl<'tcx, N: TypeFoldable<'tcx>> TypeFoldable<'tcx> for traits::VtableClosureData<'tcx, N> {
@@ -225,6 +167,10 @@ impl<'tcx, N: TypeFoldable<'tcx>> TypeFoldable<'tcx> for traits::VtableClosureDa
             nested: self.nested.fold_with(folder),
         }
     }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.substs.visit_with(visitor) || self.nested.visit_with(visitor)
+    }
 }
 
 impl<'tcx, N: TypeFoldable<'tcx>> TypeFoldable<'tcx> for traits::VtableDefaultImplData<N> {
@@ -234,6 +180,10 @@ impl<'tcx, N: TypeFoldable<'tcx>> TypeFoldable<'tcx> for traits::VtableDefaultIm
             nested: self.nested.fold_with(folder),
         }
     }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.nested.visit_with(visitor)
+    }
 }
 
 impl<'tcx, N: TypeFoldable<'tcx>> TypeFoldable<'tcx> for traits::VtableBuiltinData<N> {
@@ -242,6 +192,10 @@ impl<'tcx, N: TypeFoldable<'tcx>> TypeFoldable<'tcx> for traits::VtableBuiltinDa
             nested: self.nested.fold_with(folder),
         }
     }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.nested.visit_with(visitor)
+    }
 }
 
 impl<'tcx> TypeFoldable<'tcx> for traits::VtableObjectData<'tcx> {
@@ -251,6 +205,10 @@ impl<'tcx> TypeFoldable<'tcx> for traits::VtableObjectData<'tcx> {
             vtable_base: self.vtable_base
         }
     }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.upcast_trait_ref.visit_with(visitor)
+    }
 }
 
 impl<'tcx, N: TypeFoldable<'tcx>> TypeFoldable<'tcx> for traits::Vtable<'tcx, N> {
@@ -269,6 +227,18 @@ impl<'tcx, N: TypeFoldable<'tcx>> TypeFoldable<'tcx> for traits::Vtable<'tcx, N>
             traits::VtableObject(ref d) => traits::VtableObject(d.fold_with(folder)),
         }
     }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        match *self {
+            traits::VtableImpl(ref v) => v.visit_with(visitor),
+            traits::VtableDefaultImpl(ref t) => t.visit_with(visitor),
+            traits::VtableClosure(ref d) => d.visit_with(visitor),
+            traits::VtableFnPointer(ref d) => d.visit_with(visitor),
+            traits::VtableParam(ref n) => n.visit_with(visitor),
+            traits::VtableBuiltin(ref d) => d.visit_with(visitor),
+            traits::VtableObject(ref d) => d.visit_with(visitor),
+        }
+    }
 }
 
 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Normalized<'tcx, T> {
@@ -278,4 +248,8 @@ impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Normalized<'tcx, T> {
             obligations: self.obligations.fold_with(folder),
         }
     }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.value.visit_with(visitor) || self.obligations.visit_with(visitor)
+    }
 }
diff --git a/src/librustc/middle/ty/fold.rs b/src/librustc/middle/ty/fold.rs
index 605e78e9281..8d68c1da7f8 100644
--- a/src/librustc/middle/ty/fold.rs
+++ b/src/librustc/middle/ty/fold.rs
@@ -14,41 +14,51 @@
 //! instance of a "folder" (a type which implements `TypeFolder`). Then
 //! the setup is intended to be:
 //!
-//!     T.fold_with(F) --calls--> F.fold_T(T) --calls--> super_fold_T(F, T)
+//!   T.fold_with(F) --calls--> F.fold_T(T) --calls--> T.fold_subitems_with(F)
 //!
 //! This way, when you define a new folder F, you can override
-//! `fold_T()` to customize the behavior, and invoke `super_fold_T()`
+//! `fold_T()` to customize the behavior, and invoke `T.fold_subitems_with()`
 //! to get the original behavior. Meanwhile, to actually fold
 //! something, you can just write `T.fold_with(F)`, which is
 //! convenient. (Note that `fold_with` will also transparently handle
 //! things like a `Vec<T>` where T is foldable and so on.)
 //!
 //! In this ideal setup, the only function that actually *does*
-//! anything is `super_fold_T`, which traverses the type `T`. Moreover,
-//! `super_fold_T` should only ever call `T.fold_with()`.
+//! anything is `T.fold_subitems_with()`, which traverses the type `T`.
+//! Moreover, `T.fold_subitems_with()` should only ever call `T.fold_with()`.
 //!
 //! In some cases, we follow a degenerate pattern where we do not have
-//! a `fold_T` nor `super_fold_T` method. Instead, `T.fold_with`
-//! traverses the structure directly. This is suboptimal because the
-//! behavior cannot be overridden, but it's much less work to implement.
-//! If you ever *do* need an override that doesn't exist, it's not hard
-//! to convert the degenerate pattern into the proper thing.
+//! a `fold_T` method. Instead, `T.fold_with` traverses the structure directly.
+//! This is suboptimal because the behavior cannot be overridden, but it's
+//! much less work to implement. If you ever *do* need an override that
+//! doesn't exist, it's not hard to convert the degenerate pattern into the
+//! proper thing.
+//!
+//! A `TypeFoldable` T can also be visited by a `TypeVisitor` V using similar setup:
+//!   T.visit_with(V) --calls--> V.visit_T(T) --calls--> T.visit_subitems_with(V).
+//! These methods return true to indicate that the visitor has found what it is looking for
+//! and does not need to visit anything else.
 
 use middle::region;
 use middle::subst;
 use middle::ty::adjustment;
-use middle::ty::{self, Binder, Ty, RegionEscape};
+use middle::ty::{self, Binder, Ty, RegionEscape, HasTypeFlags};
 
 use std::fmt;
 use util::nodemap::{FnvHashMap, FnvHashSet};
 
-///////////////////////////////////////////////////////////////////////////
-// Two generic traits
-
 /// The TypeFoldable trait is implemented for every type that can be folded.
 /// Basically, every type that has a corresponding method in TypeFolder.
 pub trait TypeFoldable<'tcx>: fmt::Debug + Clone {
     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self;
+    fn fold_subitems_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
+        self.fold_with(folder)
+    }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool;
+    fn visit_subitems_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.visit_with(visitor)
+    }
 }
 
 /// The TypeFolder trait defines the actual *folding*. There is a
@@ -74,248 +84,77 @@ pub trait TypeFolder<'tcx> : Sized {
         where T : TypeFoldable<'tcx>
     {
         // FIXME(#20526) this should replace `enter_region_binder`/`exit_region_binder`.
-        super_fold_binder(self, t)
+        t.fold_subitems_with(self)
     }
 
     fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
-        super_fold_ty(self, t)
+        t.fold_subitems_with(self)
     }
 
     fn fold_mt(&mut self, t: &ty::TypeAndMut<'tcx>) -> ty::TypeAndMut<'tcx> {
-        super_fold_mt(self, t)
+        t.fold_subitems_with(self)
     }
 
     fn fold_trait_ref(&mut self, t: &ty::TraitRef<'tcx>) -> ty::TraitRef<'tcx> {
-        super_fold_trait_ref(self, t)
+        t.fold_subitems_with(self)
     }
 
     fn fold_substs(&mut self,
                    substs: &subst::Substs<'tcx>)
                    -> subst::Substs<'tcx> {
-        super_fold_substs(self, substs)
+        substs.fold_subitems_with(self)
     }
 
     fn fold_fn_sig(&mut self,
                    sig: &ty::FnSig<'tcx>)
                    -> ty::FnSig<'tcx> {
-        super_fold_fn_sig(self, sig)
+        sig.fold_subitems_with(self)
     }
 
     fn fold_output(&mut self,
                       output: &ty::FnOutput<'tcx>)
                       -> ty::FnOutput<'tcx> {
-        super_fold_output(self, output)
+        output.fold_subitems_with(self)
     }
 
     fn fold_bare_fn_ty(&mut self,
                        fty: &ty::BareFnTy<'tcx>)
                        -> ty::BareFnTy<'tcx>
     {
-        super_fold_bare_fn_ty(self, fty)
+        fty.fold_subitems_with(self)
     }
 
     fn fold_closure_ty(&mut self,
                        fty: &ty::ClosureTy<'tcx>)
                        -> ty::ClosureTy<'tcx> {
-        super_fold_closure_ty(self, fty)
+        fty.fold_subitems_with(self)
     }
 
     fn fold_region(&mut self, r: ty::Region) -> ty::Region {
-        r
+        r.fold_subitems_with(self)
     }
 
     fn fold_existential_bounds(&mut self, s: &ty::ExistentialBounds<'tcx>)
                                -> ty::ExistentialBounds<'tcx> {
-        super_fold_existential_bounds(self, s)
+        s.fold_subitems_with(self)
     }
 
     fn fold_autoref(&mut self, ar: &adjustment::AutoRef<'tcx>)
                     -> adjustment::AutoRef<'tcx> {
-        super_fold_autoref(self, ar)
-    }
-
-    fn fold_item_substs(&mut self, i: ty::ItemSubsts<'tcx>) -> ty::ItemSubsts<'tcx> {
-        super_fold_item_substs(self, i)
+        ar.fold_subitems_with(self)
     }
 }
 
-///////////////////////////////////////////////////////////////////////////
-// "super" routines: these are the default implementations for TypeFolder.
-//
-// They should invoke `foo.fold_with()` to do recursive folding.
-
-pub fn super_fold_binder<'tcx, T, U>(this: &mut T,
-                                     binder: &Binder<U>)
-                                     -> Binder<U>
-    where T : TypeFolder<'tcx>, U : TypeFoldable<'tcx>
-{
-    this.enter_region_binder();
-    let result = Binder(binder.0.fold_with(this));
-    this.exit_region_binder();
-    result
-}
-
-pub fn super_fold_ty<'tcx, T: TypeFolder<'tcx>>(this: &mut T,
-                                                ty: Ty<'tcx>)
-                                                -> Ty<'tcx> {
-    let sty = match ty.sty {
-        ty::TyBox(typ) => {
-            ty::TyBox(typ.fold_with(this))
-        }
-        ty::TyRawPtr(ref tm) => {
-            ty::TyRawPtr(tm.fold_with(this))
-        }
-        ty::TyArray(typ, sz) => {
-            ty::TyArray(typ.fold_with(this), sz)
-        }
-        ty::TySlice(typ) => {
-            ty::TySlice(typ.fold_with(this))
-        }
-        ty::TyEnum(tid, ref substs) => {
-            let substs = substs.fold_with(this);
-            ty::TyEnum(tid, this.tcx().mk_substs(substs))
-        }
-        ty::TyTrait(box ty::TraitTy { ref principal, ref bounds }) => {
-            ty::TyTrait(box ty::TraitTy {
-                principal: principal.fold_with(this),
-                bounds: bounds.fold_with(this),
-            })
-        }
-        ty::TyTuple(ref ts) => {
-            ty::TyTuple(ts.fold_with(this))
-        }
-        ty::TyBareFn(opt_def_id, ref f) => {
-            let bfn = f.fold_with(this);
-            ty::TyBareFn(opt_def_id, this.tcx().mk_bare_fn(bfn))
-        }
-        ty::TyRef(r, ref tm) => {
-            let r = r.fold_with(this);
-            ty::TyRef(this.tcx().mk_region(r), tm.fold_with(this))
-        }
-        ty::TyStruct(did, ref substs) => {
-            let substs = substs.fold_with(this);
-            ty::TyStruct(did, this.tcx().mk_substs(substs))
-        }
-        ty::TyClosure(did, ref substs) => {
-            let s = substs.fold_with(this);
-            ty::TyClosure(did, s)
-        }
-        ty::TyProjection(ref data) => {
-            ty::TyProjection(data.fold_with(this))
-        }
-        ty::TyBool | ty::TyChar | ty::TyStr |
-        ty::TyInt(_) | ty::TyUint(_) | ty::TyFloat(_) |
-        ty::TyError | ty::TyInfer(_) |
-        ty::TyParam(..) => {
-            ty.sty.clone()
-        }
-    };
-    this.tcx().mk_ty(sty)
-}
-
-pub fn super_fold_substs<'tcx, T: TypeFolder<'tcx>>(this: &mut T,
-                                                    substs: &subst::Substs<'tcx>)
-                                                    -> subst::Substs<'tcx> {
-    let regions = match substs.regions {
-        subst::ErasedRegions => {
-            subst::ErasedRegions
-        }
-        subst::NonerasedRegions(ref regions) => {
-            subst::NonerasedRegions(regions.fold_with(this))
-        }
-    };
-
-    subst::Substs { regions: regions,
-                    types: substs.types.fold_with(this) }
-}
-
-pub fn super_fold_fn_sig<'tcx, T: TypeFolder<'tcx>>(this: &mut T,
-                                                    sig: &ty::FnSig<'tcx>)
-                                                    -> ty::FnSig<'tcx>
-{
-    ty::FnSig { inputs: sig.inputs.fold_with(this),
-                output: sig.output.fold_with(this),
-                variadic: sig.variadic }
-}
-
-pub fn super_fold_output<'tcx, T: TypeFolder<'tcx>>(this: &mut T,
-                                                    output: &ty::FnOutput<'tcx>)
-                                                    -> ty::FnOutput<'tcx> {
-    match *output {
-        ty::FnConverging(ref ty) => ty::FnConverging(ty.fold_with(this)),
-        ty::FnDiverging => ty::FnDiverging
-    }
-}
-
-pub fn super_fold_bare_fn_ty<'tcx, T: TypeFolder<'tcx>>(this: &mut T,
-                                                        fty: &ty::BareFnTy<'tcx>)
-                                                        -> ty::BareFnTy<'tcx>
-{
-    ty::BareFnTy { sig: fty.sig.fold_with(this),
-                   abi: fty.abi,
-                   unsafety: fty.unsafety }
-}
-
-pub fn super_fold_closure_ty<'tcx, T: TypeFolder<'tcx>>(this: &mut T,
-                                                        fty: &ty::ClosureTy<'tcx>)
-                                                        -> ty::ClosureTy<'tcx>
-{
-    ty::ClosureTy {
-        sig: fty.sig.fold_with(this),
-        unsafety: fty.unsafety,
-        abi: fty.abi,
-    }
-}
-
-pub fn super_fold_trait_ref<'tcx, T: TypeFolder<'tcx>>(this: &mut T,
-                                                       t: &ty::TraitRef<'tcx>)
-                                                       -> ty::TraitRef<'tcx>
-{
-    let substs = t.substs.fold_with(this);
-    ty::TraitRef {
-        def_id: t.def_id,
-        substs: this.tcx().mk_substs(substs),
-    }
-}
-
-pub fn super_fold_mt<'tcx, T: TypeFolder<'tcx>>(this: &mut T,
-                                                mt: &ty::TypeAndMut<'tcx>)
-                                                -> ty::TypeAndMut<'tcx> {
-    ty::TypeAndMut {ty: mt.ty.fold_with(this),
-            mutbl: mt.mutbl}
-}
-
-pub fn super_fold_existential_bounds<'tcx, T: TypeFolder<'tcx>>(
-    this: &mut T,
-    bounds: &ty::ExistentialBounds<'tcx>)
-    -> ty::ExistentialBounds<'tcx>
-{
-    ty::ExistentialBounds {
-        region_bound: bounds.region_bound.fold_with(this),
-        builtin_bounds: bounds.builtin_bounds,
-        projection_bounds: bounds.projection_bounds.fold_with(this),
-    }
-}
+pub trait TypeVisitor<'tcx> : Sized {
+    fn enter_region_binder(&mut self) { }
+    fn exit_region_binder(&mut self) { }
 
-pub fn super_fold_autoref<'tcx, T: TypeFolder<'tcx>>(this: &mut T,
-                                                     autoref: &adjustment::AutoRef<'tcx>)
-                                                     -> adjustment::AutoRef<'tcx>
-{
-    match *autoref {
-        adjustment::AutoPtr(r, m) => {
-            let r = r.fold_with(this);
-            adjustment::AutoPtr(this.tcx().mk_region(r), m)
-        }
-        adjustment::AutoUnsafe(m) => adjustment::AutoUnsafe(m)
+    fn visit_ty(&mut self, t: Ty<'tcx>) -> bool {
+        t.visit_subitems_with(self)
     }
-}
 
-pub fn super_fold_item_substs<'tcx, T: TypeFolder<'tcx>>(this: &mut T,
-                                                         substs: ty::ItemSubsts<'tcx>)
-                                                         -> ty::ItemSubsts<'tcx>
-{
-    ty::ItemSubsts {
-        substs: substs.substs.fold_with(this),
+    fn visit_region(&mut self, r: ty::Region) -> bool {
+        r.visit_subitems_with(self)
     }
 }
 
@@ -333,7 +172,7 @@ impl<'a, 'tcx, F> TypeFolder<'tcx> for BottomUpFolder<'a, 'tcx, F> where
     fn tcx(&self) -> &ty::ctxt<'tcx> { self.tcx }
 
     fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
-        let t1 = super_fold_ty(self, ty);
+        let t1 = ty.fold_subitems_with(self);
         (self.fldop)(t1)
     }
 }
@@ -495,7 +334,7 @@ impl<'tcx> ty::ctxt<'tcx> {
     }
 
     pub fn no_late_bound_regions<T>(&self, value: &Binder<T>) -> Option<T>
-        where T : TypeFoldable<'tcx> + RegionEscape
+        where T : TypeFoldable<'tcx>
     {
         if value.0.has_escaping_regions() {
             None
@@ -561,7 +400,7 @@ impl<'a, 'tcx> TypeFolder<'tcx> for RegionReplacer<'a, 'tcx>
             return t;
         }
 
-        super_fold_ty(self, t)
+        t.fold_subitems_with(self)
     }
 
     fn fold_region(&mut self, r: ty::Region) -> ty::Region {
@@ -612,7 +451,7 @@ impl<'tcx> ty::ctxt<'tcx> {
                     Some(u) => return u
                 }
 
-                let t_norm = ty::fold::super_fold_ty(self, ty);
+                let t_norm = ty.fold_subitems_with(self);
                 self.tcx().normalized_cache.borrow_mut().insert(ty, t_norm);
                 return t_norm;
             }
@@ -621,7 +460,7 @@ impl<'tcx> ty::ctxt<'tcx> {
                 where T : TypeFoldable<'tcx>
             {
                 let u = self.tcx().anonymize_late_bound_regions(t);
-                ty::fold::super_fold_binder(self, &u)
+                u.fold_subitems_with(self)
             }
 
             fn fold_region(&mut self, r: ty::Region) -> ty::Region {
@@ -678,3 +517,65 @@ pub fn shift_regions<'tcx, T:TypeFoldable<'tcx>>(tcx: &ty::ctxt<'tcx>,
         shift_region(region, amount)
     }))
 }
+
+impl<'tcx, T: TypeFoldable<'tcx>> RegionEscape for T {
+    fn has_regions_escaping_depth(&self, depth: u32) -> bool {
+        struct RegionEscapeVisitor {
+            depth: u32,
+        }
+
+        impl<'tcx> TypeVisitor<'tcx> for RegionEscapeVisitor {
+            fn enter_region_binder(&mut self) {
+                self.depth += 1;
+            }
+
+            fn exit_region_binder(&mut self) {
+                self.depth -= 1;
+            }
+
+            fn visit_ty(&mut self, t: Ty<'tcx>) -> bool {
+                t.region_depth > self.depth
+            }
+
+            fn visit_region(&mut self, r: ty::Region) -> bool {
+                r.escapes_depth(self.depth)
+            }
+        }
+
+        self.visit_with(&mut RegionEscapeVisitor { depth: depth })
+    }
+}
+
+impl<'tcx, T: TypeFoldable<'tcx>> HasTypeFlags for T {
+    fn has_type_flags(&self, flags: ty::TypeFlags) -> bool {
+        struct HasTypeFlagsVisitor {
+            flags: ty::TypeFlags,
+        }
+
+        impl<'tcx> TypeVisitor<'tcx> for HasTypeFlagsVisitor {
+            fn visit_ty(&mut self, t: Ty) -> bool {
+                t.flags.get().intersects(self.flags)
+            }
+
+            fn visit_region(&mut self, r: ty::Region) -> bool {
+                if self.flags.intersects(ty::TypeFlags::HAS_LOCAL_NAMES) {
+                    // does this represent a region that cannot be named
+                    // in a global way? used in fulfillment caching.
+                    match r {
+                        ty::ReStatic | ty::ReEmpty => {}
+                        _ => return true,
+                    }
+                }
+                if self.flags.intersects(ty::TypeFlags::HAS_RE_INFER) {
+                    match r {
+                        ty::ReVar(_) | ty::ReSkolemized(..) => { return true }
+                        _ => {}
+                    }
+                }
+                false
+            }
+        }
+
+        self.visit_with(&mut HasTypeFlagsVisitor { flags: flags })
+    }
+}
diff --git a/src/librustc/middle/ty/relate.rs b/src/librustc/middle/ty/relate.rs
index ff0a9789cf1..137f60572bb 100644
--- a/src/librustc/middle/ty/relate.rs
+++ b/src/librustc/middle/ty/relate.rs
@@ -15,7 +15,7 @@
 
 use middle::def_id::DefId;
 use middle::subst::{ErasedRegions, NonerasedRegions, ParamSpace, Substs};
-use middle::ty::{self, HasTypeFlags, Ty};
+use middle::ty::{self, Ty};
 use middle::ty::error::{ExpectedFound, TypeError};
 use middle::ty::fold::TypeFoldable;
 use std::rc::Rc;
@@ -80,7 +80,7 @@ pub trait TypeRelation<'a,'tcx> : Sized {
         where T: Relate<'a,'tcx>;
 }
 
-pub trait Relate<'a,'tcx>: TypeFoldable<'tcx> + HasTypeFlags {
+pub trait Relate<'a,'tcx>: TypeFoldable<'tcx> {
     fn relate<R:TypeRelation<'a,'tcx>>(relation: &mut R,
                                        a: &Self,
                                        b: &Self)
diff --git a/src/librustc/middle/ty/structural_impls.rs b/src/librustc/middle/ty/structural_impls.rs
index ecb2b85fd77..8d3a93e72f5 100644
--- a/src/librustc/middle/ty/structural_impls.rs
+++ b/src/librustc/middle/ty/structural_impls.rs
@@ -11,8 +11,8 @@
 use middle::subst::{self, VecPerParamSpace};
 use middle::traits;
 use middle::ty::{self, TraitRef, Ty, TypeAndMut};
-use middle::ty::{HasTypeFlags, Lift, TypeFlags, RegionEscape};
-use middle::ty::fold::{TypeFoldable, TypeFolder};
+use middle::ty::Lift;
+use middle::ty::fold::{TypeFoldable, TypeFolder, TypeVisitor};
 
 use std::rc::Rc;
 use syntax::abi;
@@ -20,390 +20,6 @@ use syntax::ptr::P;
 
 use rustc_front::hir;
 
-// FIXME(#20298) -- all of these traits basically walk various
-// structures to test whether types/regions are reachable with various
-// properties. It should be possible to express them in terms of one
-// common "walker" trait or something.
-
-impl<'tcx> RegionEscape for Ty<'tcx> {
-    fn has_regions_escaping_depth(&self, depth: u32) -> bool {
-        self.region_depth > depth
-    }
-}
-
-impl<'tcx> RegionEscape for ty::TraitTy<'tcx> {
-    fn has_regions_escaping_depth(&self, depth: u32) -> bool {
-        self.principal.has_regions_escaping_depth(depth) ||
-            self.bounds.has_regions_escaping_depth(depth)
-    }
-}
-
-impl<'tcx> RegionEscape for ty::ExistentialBounds<'tcx> {
-    fn has_regions_escaping_depth(&self, depth: u32) -> bool {
-        self.region_bound.has_regions_escaping_depth(depth) ||
-            self.projection_bounds.has_regions_escaping_depth(depth)
-    }
-}
-
-impl<'tcx> RegionEscape for ty::InstantiatedPredicates<'tcx> {
-    fn has_regions_escaping_depth(&self, depth: u32) -> bool {
-        self.predicates.has_regions_escaping_depth(depth)
-    }
-}
-
-impl<'tcx> RegionEscape for subst::Substs<'tcx> {
-    fn has_regions_escaping_depth(&self, depth: u32) -> bool {
-        self.types.has_regions_escaping_depth(depth) ||
-            self.regions.has_regions_escaping_depth(depth)
-    }
-}
-
-impl<'tcx> RegionEscape for ty::ClosureSubsts<'tcx> {
-    fn has_regions_escaping_depth(&self, depth: u32) -> bool {
-        self.func_substs.has_regions_escaping_depth(depth) ||
-            self.upvar_tys.iter().any(|t| t.has_regions_escaping_depth(depth))
-    }
-}
-
-impl<T:RegionEscape> RegionEscape for Vec<T> {
-    fn has_regions_escaping_depth(&self, depth: u32) -> bool {
-        self.iter().any(|t| t.has_regions_escaping_depth(depth))
-    }
-}
-
-impl<'tcx> RegionEscape for ty::FnSig<'tcx> {
-    fn has_regions_escaping_depth(&self, depth: u32) -> bool {
-        self.inputs.has_regions_escaping_depth(depth) ||
-            self.output.has_regions_escaping_depth(depth)
-    }
-}
-
-impl<'tcx,T:RegionEscape> RegionEscape for VecPerParamSpace<T> {
-    fn has_regions_escaping_depth(&self, depth: u32) -> bool {
-        self.iter_enumerated().any(|(space, _, t)| {
-            if space == subst::FnSpace {
-                t.has_regions_escaping_depth(depth+1)
-            } else {
-                t.has_regions_escaping_depth(depth)
-            }
-        })
-    }
-}
-
-impl<'tcx> RegionEscape for ty::TypeScheme<'tcx> {
-    fn has_regions_escaping_depth(&self, depth: u32) -> bool {
-        self.ty.has_regions_escaping_depth(depth)
-    }
-}
-
-impl RegionEscape for ty::Region {
-    fn has_regions_escaping_depth(&self, depth: u32) -> bool {
-        self.escapes_depth(depth)
-    }
-}
-
-impl<'tcx> RegionEscape for ty::GenericPredicates<'tcx> {
-    fn has_regions_escaping_depth(&self, depth: u32) -> bool {
-        self.predicates.has_regions_escaping_depth(depth)
-    }
-}
-
-impl<'tcx> RegionEscape for ty::Predicate<'tcx> {
-    fn has_regions_escaping_depth(&self, depth: u32) -> bool {
-        match *self {
-            ty::Predicate::Trait(ref data) => data.has_regions_escaping_depth(depth),
-            ty::Predicate::Equate(ref data) => data.has_regions_escaping_depth(depth),
-            ty::Predicate::RegionOutlives(ref data) => data.has_regions_escaping_depth(depth),
-            ty::Predicate::TypeOutlives(ref data) => data.has_regions_escaping_depth(depth),
-            ty::Predicate::Projection(ref data) => data.has_regions_escaping_depth(depth),
-            ty::Predicate::WellFormed(ty) => ty.has_regions_escaping_depth(depth),
-            ty::Predicate::ObjectSafe(_trait_def_id) => false,
-        }
-    }
-}
-
-impl<'tcx> RegionEscape for TraitRef<'tcx> {
-    fn has_regions_escaping_depth(&self, depth: u32) -> bool {
-        self.substs.types.iter().any(|t| t.has_regions_escaping_depth(depth)) ||
-            self.substs.regions.has_regions_escaping_depth(depth)
-    }
-}
-
-impl<'tcx> RegionEscape for subst::RegionSubsts {
-    fn has_regions_escaping_depth(&self, depth: u32) -> bool {
-        match *self {
-            subst::ErasedRegions => false,
-            subst::NonerasedRegions(ref r) => {
-                r.iter().any(|t| t.has_regions_escaping_depth(depth))
-            }
-        }
-    }
-}
-
-impl<'tcx,T:RegionEscape> RegionEscape for ty::Binder<T> {
-    fn has_regions_escaping_depth(&self, depth: u32) -> bool {
-        self.0.has_regions_escaping_depth(depth + 1)
-    }
-}
-
-impl<'tcx> RegionEscape for ty::FnOutput<'tcx> {
-    fn has_regions_escaping_depth(&self, depth: u32) -> bool {
-        match *self {
-            ty::FnConverging(t) => t.has_regions_escaping_depth(depth),
-            ty::FnDiverging => false
-        }
-    }
-}
-
-impl<'tcx> RegionEscape for ty::EquatePredicate<'tcx> {
-    fn has_regions_escaping_depth(&self, depth: u32) -> bool {
-        self.0.has_regions_escaping_depth(depth) || self.1.has_regions_escaping_depth(depth)
-    }
-}
-
-impl<'tcx> RegionEscape for ty::TraitPredicate<'tcx> {
-    fn has_regions_escaping_depth(&self, depth: u32) -> bool {
-        self.trait_ref.has_regions_escaping_depth(depth)
-    }
-}
-
-impl<T:RegionEscape,U:RegionEscape> RegionEscape for ty::OutlivesPredicate<T,U> {
-    fn has_regions_escaping_depth(&self, depth: u32) -> bool {
-        self.0.has_regions_escaping_depth(depth) || self.1.has_regions_escaping_depth(depth)
-    }
-}
-
-impl<'tcx> RegionEscape for ty::ProjectionPredicate<'tcx> {
-    fn has_regions_escaping_depth(&self, depth: u32) -> bool {
-        self.projection_ty.has_regions_escaping_depth(depth) ||
-            self.ty.has_regions_escaping_depth(depth)
-    }
-}
-
-impl<'tcx> RegionEscape for ty::ProjectionTy<'tcx> {
-    fn has_regions_escaping_depth(&self, depth: u32) -> bool {
-        self.trait_ref.has_regions_escaping_depth(depth)
-    }
-}
-
-impl HasTypeFlags for () {
-    fn has_type_flags(&self, _flags: TypeFlags) -> bool {
-        false
-    }
-}
-
-impl<'tcx,T:HasTypeFlags> HasTypeFlags for Vec<T> {
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        self[..].has_type_flags(flags)
-    }
-}
-
-impl<'tcx,T:HasTypeFlags> HasTypeFlags for [T] {
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        self.iter().any(|p| p.has_type_flags(flags))
-    }
-}
-
-impl<'tcx,T:HasTypeFlags> HasTypeFlags for VecPerParamSpace<T> {
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        self.iter().any(|p| p.has_type_flags(flags))
-    }
-}
-
-impl HasTypeFlags for abi::Abi {
-    fn has_type_flags(&self, _flags: TypeFlags) -> bool {
-        false
-    }
-}
-
-impl HasTypeFlags for hir::Unsafety {
-    fn has_type_flags(&self, _flags: TypeFlags) -> bool {
-        false
-    }
-}
-
-impl HasTypeFlags for ty::BuiltinBounds {
-    fn has_type_flags(&self, _flags: TypeFlags) -> bool {
-        false
-    }
-}
-
-impl<'tcx> HasTypeFlags for ty::ClosureTy<'tcx> {
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        self.sig.has_type_flags(flags)
-    }
-}
-
-impl<'tcx> HasTypeFlags for ty::ClosureUpvar<'tcx> {
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        self.ty.has_type_flags(flags)
-    }
-}
-
-impl<'tcx> HasTypeFlags for ty::ExistentialBounds<'tcx> {
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        self.projection_bounds.has_type_flags(flags)
-    }
-}
-
-impl<'tcx> HasTypeFlags for ty::InstantiatedPredicates<'tcx> {
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        self.predicates.has_type_flags(flags)
-    }
-}
-
-impl<'tcx> HasTypeFlags for ty::Predicate<'tcx> {
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        match *self {
-            ty::Predicate::Trait(ref data) => data.has_type_flags(flags),
-            ty::Predicate::Equate(ref data) => data.has_type_flags(flags),
-            ty::Predicate::RegionOutlives(ref data) => data.has_type_flags(flags),
-            ty::Predicate::TypeOutlives(ref data) => data.has_type_flags(flags),
-            ty::Predicate::Projection(ref data) => data.has_type_flags(flags),
-            ty::Predicate::WellFormed(data) => data.has_type_flags(flags),
-            ty::Predicate::ObjectSafe(_trait_def_id) => false,
-        }
-    }
-}
-
-impl<'tcx> HasTypeFlags for ty::TraitPredicate<'tcx> {
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        self.trait_ref.has_type_flags(flags)
-    }
-}
-
-impl<'tcx> HasTypeFlags for ty::EquatePredicate<'tcx> {
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        self.0.has_type_flags(flags) || self.1.has_type_flags(flags)
-    }
-}
-
-impl HasTypeFlags for ty::Region {
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        if flags.intersects(TypeFlags::HAS_LOCAL_NAMES) {
-            // does this represent a region that cannot be named in a global
-            // way? used in fulfillment caching.
-            match *self {
-                ty::ReStatic | ty::ReEmpty => {}
-                _ => return true
-            }
-        }
-        if flags.intersects(TypeFlags::HAS_RE_INFER) {
-            match *self {
-                ty::ReVar(_) | ty::ReSkolemized(..) => { return true }
-                _ => {}
-            }
-        }
-        false
-    }
-}
-
-impl<T:HasTypeFlags,U:HasTypeFlags> HasTypeFlags for ty::OutlivesPredicate<T,U> {
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        self.0.has_type_flags(flags) || self.1.has_type_flags(flags)
-    }
-}
-
-impl<'tcx> HasTypeFlags for ty::ProjectionPredicate<'tcx> {
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        self.projection_ty.has_type_flags(flags) || self.ty.has_type_flags(flags)
-    }
-}
-
-impl<'tcx> HasTypeFlags for ty::ProjectionTy<'tcx> {
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        self.trait_ref.has_type_flags(flags)
-    }
-}
-
-impl<'tcx> HasTypeFlags for Ty<'tcx> {
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        self.flags.get().intersects(flags)
-    }
-}
-
-impl<'tcx> HasTypeFlags for TypeAndMut<'tcx> {
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        self.ty.has_type_flags(flags)
-    }
-}
-
-impl<'tcx> HasTypeFlags for TraitRef<'tcx> {
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        self.substs.has_type_flags(flags)
-    }
-}
-
-impl<'tcx> HasTypeFlags for subst::Substs<'tcx> {
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        self.types.has_type_flags(flags) || match self.regions {
-            subst::ErasedRegions => false,
-            subst::NonerasedRegions(ref r) => r.has_type_flags(flags)
-        }
-    }
-}
-
-impl<'tcx,T> HasTypeFlags for Option<T>
-    where T : HasTypeFlags
-{
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        self.iter().any(|t| t.has_type_flags(flags))
-    }
-}
-
-impl<'tcx,T> HasTypeFlags for Rc<T>
-    where T : HasTypeFlags
-{
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        (**self).has_type_flags(flags)
-    }
-}
-
-impl<'tcx,T> HasTypeFlags for Box<T>
-    where T : HasTypeFlags
-{
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        (**self).has_type_flags(flags)
-    }
-}
-
-impl<T> HasTypeFlags for ty::Binder<T>
-    where T : HasTypeFlags
-{
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        self.0.has_type_flags(flags)
-    }
-}
-
-impl<'tcx> HasTypeFlags for ty::FnOutput<'tcx> {
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        match *self {
-            ty::FnConverging(t) => t.has_type_flags(flags),
-            ty::FnDiverging => false,
-        }
-    }
-}
-
-impl<'tcx> HasTypeFlags for ty::FnSig<'tcx> {
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        self.inputs.iter().any(|t| t.has_type_flags(flags)) ||
-            self.output.has_type_flags(flags)
-    }
-}
-
-impl<'tcx> HasTypeFlags for ty::BareFnTy<'tcx> {
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        self.sig.has_type_flags(flags)
-    }
-}
-
-impl<'tcx> HasTypeFlags for ty::ClosureSubsts<'tcx> {
-    fn has_type_flags(&self, flags: TypeFlags) -> bool {
-        self.func_substs.has_type_flags(flags) ||
-            self.upvar_tys.iter().any(|t| t.has_type_flags(flags))
-    }
-}
-
 ///////////////////////////////////////////////////////////////////////////
 // Lift implementations
 
@@ -511,6 +127,10 @@ macro_rules! CopyImpls {
                 fn fold_with<F:TypeFolder<'tcx>>(&self, _: &mut F) -> $ty {
                     *self
                 }
+
+                fn visit_with<F: TypeVisitor<'tcx>>(&self, _: &mut F) -> bool {
+                    false
+                }
             }
         )+
     }
@@ -522,18 +142,30 @@ impl<'tcx, T:TypeFoldable<'tcx>, U:TypeFoldable<'tcx>> TypeFoldable<'tcx> for (T
     fn fold_with<F:TypeFolder<'tcx>>(&self, folder: &mut F) -> (T, U) {
         (self.0.fold_with(folder), self.1.fold_with(folder))
     }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.0.visit_with(visitor) || self.1.visit_with(visitor)
+    }
 }
 
 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Option<T> {
     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Option<T> {
         self.as_ref().map(|t| t.fold_with(folder))
     }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.iter().any(|t| t.visit_with(visitor))
+    }
 }
 
 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Rc<T> {
     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Rc<T> {
         Rc::new((**self).fold_with(folder))
     }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        (**self).visit_with(visitor)
+    }
 }
 
 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Box<T> {
@@ -541,24 +173,50 @@ impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Box<T> {
         let content: T = (**self).fold_with(folder);
         box content
     }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        (**self).visit_with(visitor)
+    }
 }
 
 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Vec<T> {
     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Vec<T> {
         self.iter().map(|t| t.fold_with(folder)).collect()
     }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.iter().any(|t| t.visit_with(visitor))
+    }
 }
 
 impl<'tcx, T:TypeFoldable<'tcx>> TypeFoldable<'tcx> for ty::Binder<T> {
     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> ty::Binder<T> {
         folder.fold_binder(self)
     }
+
+    fn fold_subitems_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
+        folder.enter_region_binder();
+        let result = ty::Binder(self.0.fold_with(folder));
+        folder.exit_region_binder();
+        result
+    }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        visitor.enter_region_binder();
+        if self.0.visit_with(visitor) { return true }
+        visitor.exit_region_binder();
+        false
+    }
 }
 
 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for P<[T]> {
     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> P<[T]> {
         self.iter().map(|t| t.fold_with(folder)).collect()
     }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.iter().any(|t| t.visit_with(visitor))
+    }
 }
 
 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for VecPerParamSpace<T> {
@@ -582,60 +240,244 @@ impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for VecPerParamSpace<T> {
         }
         result
     }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        let mut entered_region_binder = false;
+        let result = self.iter_enumerated().any(|(space, index, t)| {
+            if space == subst::FnSpace && index == 0 {
+                visitor.enter_region_binder();
+                entered_region_binder = true;
+            }
+            t.visit_with(visitor)
+        });
+        if entered_region_binder {
+            visitor.exit_region_binder();
+        }
+        result
+    }
+}
+
+impl<'tcx> TypeFoldable<'tcx> for ty::TraitTy<'tcx> {
+    fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
+        ty::TraitTy {
+            principal: self.principal.fold_with(folder),
+            bounds: self.bounds.fold_with(folder),
+        }
+    }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.principal.visit_with(visitor) || self.bounds.visit_with(visitor)
+    }
 }
 
 impl<'tcx> TypeFoldable<'tcx> for Ty<'tcx> {
     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Ty<'tcx> {
         folder.fold_ty(*self)
     }
+
+    fn fold_subitems_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
+        let sty = match self.sty {
+            ty::TyBox(typ) => ty::TyBox(typ.fold_with(folder)),
+            ty::TyRawPtr(ref tm) => ty::TyRawPtr(tm.fold_with(folder)),
+            ty::TyArray(typ, sz) => ty::TyArray(typ.fold_with(folder), sz),
+            ty::TySlice(typ) => ty::TySlice(typ.fold_with(folder)),
+            ty::TyEnum(tid, ref substs) => {
+                let substs = substs.fold_with(folder);
+                ty::TyEnum(tid, folder.tcx().mk_substs(substs))
+            }
+            ty::TyTrait(ref trait_ty) => ty::TyTrait(trait_ty.fold_with(folder)),
+            ty::TyTuple(ref ts) => ty::TyTuple(ts.fold_with(folder)),
+            ty::TyBareFn(opt_def_id, ref f) => {
+                let bfn = f.fold_with(folder);
+                ty::TyBareFn(opt_def_id, folder.tcx().mk_bare_fn(bfn))
+            }
+            ty::TyRef(r, ref tm) => {
+                let r = r.fold_with(folder);
+                ty::TyRef(folder.tcx().mk_region(r), tm.fold_with(folder))
+            }
+            ty::TyStruct(did, ref substs) => {
+                let substs = substs.fold_with(folder);
+                ty::TyStruct(did, folder.tcx().mk_substs(substs))
+            }
+            ty::TyClosure(did, ref substs) => {
+                ty::TyClosure(did, substs.fold_with(folder))
+            }
+            ty::TyProjection(ref data) => ty::TyProjection(data.fold_with(folder)),
+            ty::TyBool | ty::TyChar | ty::TyStr | ty::TyInt(_) |
+            ty::TyUint(_) | ty::TyFloat(_) | ty::TyError | ty::TyInfer(_) |
+            ty::TyParam(..) => self.sty.clone(),
+        };
+        folder.tcx().mk_ty(sty)
+    }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        visitor.visit_ty(self)
+    }
+
+    fn visit_subitems_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        match self.sty {
+            ty::TyBox(typ) => typ.visit_with(visitor),
+            ty::TyRawPtr(ref tm) => tm.visit_with(visitor),
+            ty::TyArray(typ, _sz) => typ.visit_with(visitor),
+            ty::TySlice(typ) => typ.visit_with(visitor),
+            ty::TyEnum(_tid, ref substs) => substs.visit_with(visitor),
+            ty::TyTrait(ref trait_ty) => trait_ty.visit_with(visitor),
+            ty::TyTuple(ref ts) => ts.visit_with(visitor),
+            ty::TyBareFn(_opt_def_id, ref f) => f.visit_with(visitor),
+            ty::TyRef(r, ref tm) => r.visit_with(visitor) || tm.visit_with(visitor),
+            ty::TyStruct(_did, ref substs) => substs.visit_with(visitor),
+            ty::TyClosure(_did, ref substs) => substs.visit_with(visitor),
+            ty::TyProjection(ref data) => data.visit_with(visitor),
+            ty::TyBool | ty::TyChar | ty::TyStr | ty::TyInt(_) |
+            ty::TyUint(_) | ty::TyFloat(_) | ty::TyError | ty::TyInfer(_) |
+            ty::TyParam(..) => false,
+        }
+    }
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ty::BareFnTy<'tcx> {
     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> ty::BareFnTy<'tcx> {
         folder.fold_bare_fn_ty(self)
     }
+
+    fn fold_subitems_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
+        ty::BareFnTy { sig: self.sig.fold_with(folder),
+                       abi: self.abi,
+                       unsafety: self.unsafety }
+    }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.sig.visit_with(visitor)
+    }
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ty::ClosureTy<'tcx> {
     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> ty::ClosureTy<'tcx> {
         folder.fold_closure_ty(self)
     }
+
+    fn fold_subitems_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
+       ty::ClosureTy {
+            sig: self.sig.fold_with(folder),
+            unsafety: self.unsafety,
+            abi: self.abi,
+        }
+    }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.sig.visit_with(visitor)
+    }
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ty::TypeAndMut<'tcx> {
     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> ty::TypeAndMut<'tcx> {
         folder.fold_mt(self)
     }
+
+    fn fold_subitems_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
+        ty::TypeAndMut { ty: self.ty.fold_with(folder), mutbl: self.mutbl }
+    }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.ty.visit_with(visitor)
+    }
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ty::FnOutput<'tcx> {
     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> ty::FnOutput<'tcx> {
         folder.fold_output(self)
     }
+
+    fn fold_subitems_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
+        match *self {
+            ty::FnConverging(ref ty) => ty::FnConverging(ty.fold_with(folder)),
+            ty::FnDiverging => ty::FnDiverging
+        }
+    }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        match *self {
+            ty::FnConverging(ref ty) => ty.visit_with(visitor),
+            ty::FnDiverging => false,
+        }
+    }
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ty::FnSig<'tcx> {
     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> ty::FnSig<'tcx> {
         folder.fold_fn_sig(self)
     }
+
+    fn fold_subitems_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
+        ty::FnSig { inputs: self.inputs.fold_with(folder),
+                    output: self.output.fold_with(folder),
+                    variadic: self.variadic }
+    }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.inputs.visit_with(visitor) || self.output.visit_with(visitor)
+    }
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ty::TraitRef<'tcx> {
     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> ty::TraitRef<'tcx> {
         folder.fold_trait_ref(self)
     }
+
+    fn fold_subitems_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
+        let substs = self.substs.fold_with(folder);
+        ty::TraitRef {
+            def_id: self.def_id,
+            substs: folder.tcx().mk_substs(substs),
+        }
+    }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.substs.visit_with(visitor)
+    }
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ty::Region {
     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> ty::Region {
         folder.fold_region(*self)
     }
+
+    fn fold_subitems_with<F: TypeFolder<'tcx>>(&self, _folder: &mut F) -> Self {
+        *self
+    }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        visitor.visit_region(*self)
+    }
+
+    fn visit_subitems_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> bool {
+        false
+    }
 }
 
 impl<'tcx> TypeFoldable<'tcx> for subst::Substs<'tcx> {
     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> subst::Substs<'tcx> {
         folder.fold_substs(self)
     }
+
+    fn fold_subitems_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
+        let regions = match self.regions {
+            subst::ErasedRegions => subst::ErasedRegions,
+            subst::NonerasedRegions(ref regions) => {
+                subst::NonerasedRegions(regions.fold_with(folder))
+            }
+        };
+
+        subst::Substs { regions: regions,
+                        types: self.types.fold_with(folder) }
+    }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.types.visit_with(visitor) || match self.regions {
+            subst::ErasedRegions => false,
+            subst::NonerasedRegions(ref regions) => regions.visit_with(visitor),
+        }
+    }
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ty::ClosureSubsts<'tcx> {
@@ -646,6 +488,10 @@ impl<'tcx> TypeFoldable<'tcx> for ty::ClosureSubsts<'tcx> {
             upvar_tys: self.upvar_tys.fold_with(folder),
         }
     }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.func_substs.visit_with(visitor) || self.upvar_tys.visit_with(visitor)
+    }
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ty::ItemSubsts<'tcx> {
@@ -654,24 +500,61 @@ impl<'tcx> TypeFoldable<'tcx> for ty::ItemSubsts<'tcx> {
             substs: self.substs.fold_with(folder),
         }
     }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.substs.visit_with(visitor)
+    }
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ty::adjustment::AutoRef<'tcx> {
     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> ty::adjustment::AutoRef<'tcx> {
         folder.fold_autoref(self)
     }
+
+    fn fold_subitems_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
+        match *self {
+            ty::adjustment::AutoPtr(r, m) => {
+                let r = r.fold_with(folder);
+                ty::adjustment::AutoPtr(folder.tcx().mk_region(r), m)
+            }
+            ty::adjustment::AutoUnsafe(m) => ty::adjustment::AutoUnsafe(m)
+        }
+    }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        match *self {
+            ty::adjustment::AutoPtr(r, _m) => r.visit_with(visitor),
+            ty::adjustment::AutoUnsafe(_m) => false,
+        }
+    }
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ty::BuiltinBounds {
     fn fold_with<F: TypeFolder<'tcx>>(&self, _folder: &mut F) -> ty::BuiltinBounds {
         *self
     }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> bool {
+        false
+    }
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ty::ExistentialBounds<'tcx> {
     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> ty::ExistentialBounds<'tcx> {
         folder.fold_existential_bounds(self)
     }
+
+    fn fold_subitems_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
+        ty::ExistentialBounds {
+            region_bound: self.region_bound.fold_with(folder),
+            builtin_bounds: self.builtin_bounds,
+            projection_bounds: self.projection_bounds.fold_with(folder),
+        }
+    }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.region_bound.visit_with(visitor) || self.projection_bounds.visit_with(visitor)
+    }
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ty::TypeParameterDef<'tcx> {
@@ -686,6 +569,11 @@ impl<'tcx> TypeFoldable<'tcx> for ty::TypeParameterDef<'tcx> {
             object_lifetime_default: self.object_lifetime_default.fold_with(folder),
         }
     }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.default.visit_with(visitor) ||
+            self.object_lifetime_default.visit_with(visitor)
+    }
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ty::ObjectLifetimeDefault {
@@ -701,6 +589,13 @@ impl<'tcx> TypeFoldable<'tcx> for ty::ObjectLifetimeDefault {
                 ty::ObjectLifetimeDefault::Specific(r.fold_with(folder)),
         }
     }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        match *self {
+            ty::ObjectLifetimeDefault::Specific(r) => r.visit_with(visitor),
+            _ => false,
+        }
+    }
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ty::RegionParameterDef {
@@ -713,6 +608,10 @@ impl<'tcx> TypeFoldable<'tcx> for ty::RegionParameterDef {
             bounds: self.bounds.fold_with(folder)
         }
     }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.bounds.visit_with(visitor)
+    }
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ty::Generics<'tcx> {
@@ -722,6 +621,10 @@ impl<'tcx> TypeFoldable<'tcx> for ty::Generics<'tcx> {
             regions: self.regions.fold_with(folder),
         }
     }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.types.visit_with(visitor) || self.regions.visit_with(visitor)
+    }
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ty::GenericPredicates<'tcx> {
@@ -730,6 +633,10 @@ impl<'tcx> TypeFoldable<'tcx> for ty::GenericPredicates<'tcx> {
             predicates: self.predicates.fold_with(folder),
         }
     }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.predicates.visit_with(visitor)
+    }
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ty::Predicate<'tcx> {
@@ -751,6 +658,18 @@ impl<'tcx> TypeFoldable<'tcx> for ty::Predicate<'tcx> {
                 ty::Predicate::ObjectSafe(trait_def_id),
         }
     }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        match *self {
+            ty::Predicate::Trait(ref a) => a.visit_with(visitor),
+            ty::Predicate::Equate(ref binder) => binder.visit_with(visitor),
+            ty::Predicate::RegionOutlives(ref binder) => binder.visit_with(visitor),
+            ty::Predicate::TypeOutlives(ref binder) => binder.visit_with(visitor),
+            ty::Predicate::Projection(ref binder) => binder.visit_with(visitor),
+            ty::Predicate::WellFormed(data) => data.visit_with(visitor),
+            ty::Predicate::ObjectSafe(_trait_def_id) => false,
+        }
+    }
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ty::ProjectionPredicate<'tcx> {
@@ -760,6 +679,10 @@ impl<'tcx> TypeFoldable<'tcx> for ty::ProjectionPredicate<'tcx> {
             ty: self.ty.fold_with(folder),
         }
     }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.projection_ty.visit_with(visitor) || self.ty.visit_with(visitor)
+    }
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ty::ProjectionTy<'tcx> {
@@ -769,6 +692,10 @@ impl<'tcx> TypeFoldable<'tcx> for ty::ProjectionTy<'tcx> {
             item_name: self.item_name,
         }
     }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.trait_ref.visit_with(visitor)
+    }
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ty::InstantiatedPredicates<'tcx> {
@@ -777,6 +704,10 @@ impl<'tcx> TypeFoldable<'tcx> for ty::InstantiatedPredicates<'tcx> {
             predicates: self.predicates.fold_with(folder),
         }
     }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.predicates.visit_with(visitor)
+    }
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ty::EquatePredicate<'tcx> {
@@ -784,6 +715,10 @@ impl<'tcx> TypeFoldable<'tcx> for ty::EquatePredicate<'tcx> {
         ty::EquatePredicate(self.0.fold_with(folder),
                             self.1.fold_with(folder))
     }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.0.visit_with(visitor) || self.1.visit_with(visitor)
+    }
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ty::TraitPredicate<'tcx> {
@@ -792,6 +727,10 @@ impl<'tcx> TypeFoldable<'tcx> for ty::TraitPredicate<'tcx> {
             trait_ref: self.trait_ref.fold_with(folder)
         }
     }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.trait_ref.visit_with(visitor)
+    }
 }
 
 impl<'tcx,T,U> TypeFoldable<'tcx> for ty::OutlivesPredicate<T,U>
@@ -802,6 +741,10 @@ impl<'tcx,T,U> TypeFoldable<'tcx> for ty::OutlivesPredicate<T,U>
         ty::OutlivesPredicate(self.0.fold_with(folder),
                               self.1.fold_with(folder))
     }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.0.visit_with(visitor) || self.1.visit_with(visitor)
+    }
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ty::ClosureUpvar<'tcx> {
@@ -812,6 +755,10 @@ impl<'tcx> TypeFoldable<'tcx> for ty::ClosureUpvar<'tcx> {
             ty: self.ty.fold_with(folder),
         }
     }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.ty.visit_with(visitor)
+    }
 }
 
 impl<'a, 'tcx> TypeFoldable<'tcx> for ty::ParameterEnvironment<'a, 'tcx> where 'tcx: 'a {
@@ -826,4 +773,23 @@ impl<'a, 'tcx> TypeFoldable<'tcx> for ty::ParameterEnvironment<'a, 'tcx> where '
             free_id_outlive: self.free_id_outlive,
         }
     }
+
+    fn 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> TypeFoldable<'tcx> for ty::TypeScheme<'tcx>  {
+    fn fold_with<F:TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
+        ty::TypeScheme {
+            generics: self.generics.fold_with(folder),
+            ty: self.ty.fold_with(folder),
+        }
+    }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.generics.visit_with(visitor) || self.ty.visit_with(visitor)
+    }
 }
diff --git a/src/librustc/util/ppaux.rs b/src/librustc/util/ppaux.rs
index 11d3068f065..423cd62a13f 100644
--- a/src/librustc/util/ppaux.rs
+++ b/src/librustc/util/ppaux.rs
@@ -256,6 +256,10 @@ impl<'tcx> TypeFoldable<'tcx> for TraitAndProjections<'tcx> {
                                               -> TraitAndProjections<'tcx> {
         TraitAndProjections(self.0.fold_with(folder), self.1.fold_with(folder))
     }
+
+    fn visit_with<V: ty::fold::TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.0.visit_with(visitor) || self.1.visit_with(visitor)
+    }
 }
 
 impl<'tcx> fmt::Display for TraitAndProjections<'tcx> {
diff --git a/src/librustc_trans/trans/common.rs b/src/librustc_trans/trans/common.rs
index 964e981aec0..31b5839bd21 100644
--- a/src/librustc_trans/trans/common.rs
+++ b/src/librustc_trans/trans/common.rs
@@ -469,7 +469,7 @@ impl<'a, 'tcx> FunctionContext<'a, 'tcx> {
     }
 
     pub fn monomorphize<T>(&self, value: &T) -> T
-        where T : TypeFoldable<'tcx> + HasTypeFlags
+        where T : TypeFoldable<'tcx>
     {
         monomorphize::apply_param_substs(self.ccx.tcx(),
                                          self.param_substs,
@@ -650,7 +650,7 @@ impl<'blk, 'tcx> BlockS<'blk, 'tcx> {
     }
 
     pub fn monomorphize<T>(&self, value: &T) -> T
-        where T : TypeFoldable<'tcx> + HasTypeFlags
+        where T : TypeFoldable<'tcx>
     {
         monomorphize::apply_param_substs(self.tcx(),
                                          self.fcx.param_substs,
diff --git a/src/librustc_trans/trans/monomorphize.rs b/src/librustc_trans/trans/monomorphize.rs
index 80a86bac26b..0eaab6b3dbb 100644
--- a/src/librustc_trans/trans/monomorphize.rs
+++ b/src/librustc_trans/trans/monomorphize.rs
@@ -299,7 +299,7 @@ pub fn apply_param_substs<'tcx,T>(tcx: &ty::ctxt<'tcx>,
                                   param_substs: &Substs<'tcx>,
                                   value: &T)
                                   -> T
-    where T : TypeFoldable<'tcx> + HasTypeFlags
+    where T : TypeFoldable<'tcx>
 {
     let substituted = value.subst(tcx, param_substs);
     normalize_associated_type(tcx, &substituted)
diff --git a/src/librustc_typeck/check/assoc.rs b/src/librustc_typeck/check/assoc.rs
index 8dc95562e44..91916efa882 100644
--- a/src/librustc_typeck/check/assoc.rs
+++ b/src/librustc_typeck/check/assoc.rs
@@ -11,7 +11,6 @@
 use middle::infer::InferCtxt;
 use middle::traits::{self, FulfillmentContext, Normalized, MiscObligation,
                      SelectionContext, ObligationCause};
-use middle::ty::HasTypeFlags;
 use middle::ty::fold::TypeFoldable;
 use syntax::ast;
 use syntax::codemap::Span;
@@ -23,7 +22,7 @@ pub fn normalize_associated_types_in<'a,'tcx,T>(infcx: &InferCtxt<'a,'tcx>,
                                                 body_id: ast::NodeId,
                                                 value: &T)
                                                 -> T
-    where T : TypeFoldable<'tcx> + HasTypeFlags
+    where T : TypeFoldable<'tcx>
 {
     debug!("normalize_associated_types_in(value={:?})", value);
     let mut selcx = SelectionContext::new(infcx);
diff --git a/src/librustc_typeck/check/mod.rs b/src/librustc_typeck/check/mod.rs
index 14adc84f701..f99124664bb 100644
--- a/src/librustc_typeck/check/mod.rs
+++ b/src/librustc_typeck/check/mod.rs
@@ -318,7 +318,7 @@ impl<'a, 'tcx> Inherited<'a, 'tcx> {
                                         body_id: ast::NodeId,
                                         value: &T)
                                         -> T
-        where T : TypeFoldable<'tcx> + HasTypeFlags
+        where T : TypeFoldable<'tcx>
     {
         let mut fulfillment_cx = self.infcx.fulfillment_cx.borrow_mut();
         assoc::normalize_associated_types_in(&self.infcx,
@@ -1334,7 +1334,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                   substs: &Substs<'tcx>,
                                   value: &T)
                                   -> T
-        where T : TypeFoldable<'tcx> + HasTypeFlags
+        where T : TypeFoldable<'tcx>
     {
         let value = value.subst(self.tcx(), substs);
         let result = self.normalize_associated_types_in(span, &value);
@@ -1360,7 +1360,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
 
     fn normalize_associated_types_in<T>(&self, span: Span, value: &T) -> T
-        where T : TypeFoldable<'tcx> + HasTypeFlags
+        where T : TypeFoldable<'tcx>
     {
         self.inh.normalize_associated_types_in(span, self.body_id, value)
     }