Auto merge of #30317 - jseyfried:refactor_type_folder, r=nikomatsakis

`TypeFoldable`s can currently be visited inefficiently with an identity folder that is run only for its side effects. This creates a more efficient visitor for `TypeFoldable`s and uses it to implement `RegionEscape` and `HasProjectionTypes`, fixing cleanup issue #20298.
This is a pure refactoring.

src/librustc/middle/implicator.rs

@@ -14,7 +14,7 @@ use middle::def_id::DefId;
 use middle::infer::{InferCtxt, GenericKind};
 use middle::subst::Substs;
 use middle::traits;
-use middle::ty::{self, RegionEscape, ToPredicate, Ty};
+use middle::ty::{self, ToPredicate, Ty};
 use middle::ty::fold::{TypeFoldable, TypeFolder};
 
 use syntax::ast;
@@ -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,

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.super_fold_with(self)
             }
         }
     }

src/librustc/middle/infer/error_reporting.rs

@@ -82,7 +82,7 @@ use middle::def_id::DefId;
 use middle::infer::{self, TypeOrigin};
 use middle::region;
 use middle::subst;
-use middle::ty::{self, Ty, HasTypeFlags};
+use middle::ty::{self, Ty, TypeFoldable};
 use middle::ty::{Region, ReFree};
 use middle::ty::error::TypeError;
 
@@ -250,7 +250,7 @@ pub trait ErrorReporting<'tcx> {
 
     fn values_str(&self, values: &ValuePairs<'tcx>) -> Option<String>;
 
-    fn expected_found_str<T: fmt::Display + Resolvable<'tcx> + HasTypeFlags>(
+    fn expected_found_str<T: fmt::Display + Resolvable<'tcx> + TypeFoldable<'tcx>>(
         &self,
         exp_found: &ty::error::ExpectedFound<T>)
         -> Option<String>;
@@ -575,7 +575,7 @@ impl<'a, 'tcx> ErrorReporting<'tcx> for InferCtxt<'a, 'tcx> {
         }
     }
 
-    fn expected_found_str<T: fmt::Display + Resolvable<'tcx> + HasTypeFlags>(
+    fn expected_found_str<T: fmt::Display + Resolvable<'tcx> + TypeFoldable<'tcx>>(
         &self,
         exp_found: &ty::error::ExpectedFound<T>)
         -> Option<String>

src/librustc/middle/infer/freshen.rs

@@ -30,8 +30,7 @@
 //! variable only once, and it does so as soon as it can, so it is reasonable to ask what the type
 //! inferencer knows "so far".
 
-use middle::ty::{self, Ty, HasTypeFlags};
-use middle::ty::fold::TypeFoldable;
+use middle::ty::{self, Ty, TypeFoldable};
 use middle::ty::fold::TypeFolder;
 use std::collections::hash_map::{self, Entry};
 
@@ -169,7 +168,7 @@ impl<'a, 'tcx> TypeFolder<'tcx> for TypeFreshener<'a, 'tcx> {
             ty::TyTuple(..) |
             ty::TyProjection(..) |
             ty::TyParam(..) => {
-                ty::fold::super_fold_ty(self, t)
+                t.super_fold_with(self)
             }
         }
     }

src/librustc/middle/infer/higher_ranked/mod.rs

@@ -14,9 +14,8 @@
 use super::{CombinedSnapshot, InferCtxt, HigherRankedType, SkolemizationMap};
 use super::combine::CombineFields;
 
-use middle::ty::{self, Binder};
+use middle::ty::{self, Binder, TypeFoldable};
 use middle::ty::error::TypeError;
-use middle::ty::fold::TypeFoldable;
 use middle::ty::relate::{Relate, RelateResult, TypeRelation};
 use syntax::codemap::Span;
 use util::nodemap::{FnvHashMap, FnvHashSet};
@@ -557,7 +556,7 @@ pub fn plug_leaks<'a,'tcx,T>(infcx: &InferCtxt<'a,'tcx>,
                              snapshot: &CombinedSnapshot,
                              value: &T)
                              -> T
-    where T : TypeFoldable<'tcx> + ty::HasTypeFlags
+    where T : TypeFoldable<'tcx>
 {
     debug_assert!(leak_check(infcx, &skol_map, snapshot).is_ok());
 

src/librustc/middle/infer/mod.rs

@@ -30,7 +30,7 @@ use middle::subst::Subst;
 use middle::traits;
 use middle::ty::adjustment;
 use middle::ty::{TyVid, IntVid, FloatVid};
-use middle::ty::{self, Ty, HasTypeFlags};
+use middle::ty::{self, Ty};
 use middle::ty::error::{ExpectedFound, TypeError, UnconstrainedNumeric};
 use middle::ty::fold::{TypeFolder, TypeFoldable};
 use middle::ty::relate::{Relate, RelateResult, TypeRelation};
@@ -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

src/librustc/middle/infer/resolve.rs

@@ -9,8 +9,7 @@
 // except according to those terms.
 
 use super::{InferCtxt, FixupError, FixupResult};
-use middle::ty::{self, Ty, HasTypeFlags};
-use middle::ty::fold::{TypeFoldable};
+use middle::ty::{self, Ty, TypeFoldable};
 
 ///////////////////////////////////////////////////////////////////////////
 // OPPORTUNISTIC TYPE RESOLVER
@@ -40,7 +39,7 @@ 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.super_fold_with(self)
         }
     }
 }
@@ -68,7 +67,7 @@ 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.super_fold_with(self)
         }
     }
 
@@ -133,7 +132,7 @@ impl<'a, 'tcx> ty::fold::TypeFolder<'tcx> for FullTypeResolver<'a, 'tcx> {
                                 t));
                 }
                 _ => {
-                    ty::fold::super_fold_ty(self, t)
+                    t.super_fold_with(self)
                 }
             }
         }

src/librustc/middle/intrinsicck.rs

@@ -13,7 +13,7 @@ use middle::def::DefFn;
 use middle::def_id::DefId;
 use middle::subst::{Subst, Substs, EnumeratedItems};
 use middle::ty::{TransmuteRestriction, ctxt, TyBareFn};
-use middle::ty::{self, Ty, HasTypeFlags};
+use middle::ty::{self, Ty, TypeFoldable};
 
 use std::fmt;
 

src/librustc/middle/subst.rs

@@ -14,7 +14,7 @@ pub use self::ParamSpace::*;
 pub use self::RegionSubsts::*;
 
 use middle::cstore;
-use middle::ty::{self, Ty, HasTypeFlags, RegionEscape};
+use middle::ty::{self, Ty};
 use middle::ty::fold::{TypeFoldable, TypeFolder};
 
 use serialize::{Encodable, Encoder, Decodable, Decoder};
@@ -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.super_fold_with(self)
             }
         };
 

src/librustc/middle/traits/error_reporting.rs

@@ -26,9 +26,8 @@ use super::{
 use fmt_macros::{Parser, Piece, Position};
 use middle::def_id::DefId;
 use middle::infer::InferCtxt;
-use middle::ty::{self, ToPredicate, HasTypeFlags, ToPolyTraitRef, TraitRef, Ty};
+use middle::ty::{self, ToPredicate, ToPolyTraitRef, TraitRef, Ty, TypeFoldable};
 use middle::ty::fast_reject;
-use middle::ty::fold::TypeFoldable;
 use util::nodemap::{FnvHashMap, FnvHashSet};
 
 use std::cmp;
@@ -185,7 +184,7 @@ 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);

src/librustc/middle/traits/fulfill.rs

@@ -9,7 +9,7 @@
 // except according to those terms.
 
 use middle::infer::InferCtxt;
-use middle::ty::{self, RegionEscape, Ty, HasTypeFlags};
+use middle::ty::{self, Ty, TypeFoldable};
 
 use syntax::ast;
 use util::common::ErrorReported;

src/librustc/middle/traits/mod.rs

@@ -19,9 +19,8 @@ use dep_graph::DepNode;
 use middle::def_id::DefId;
 use middle::free_region::FreeRegionMap;
 use middle::subst;
-use middle::ty::{self, HasTypeFlags, Ty};
+use middle::ty::{self, Ty, TypeFoldable};
 use middle::ty::fast_reject;
-use middle::ty::fold::TypeFoldable;
 use middle::infer::{self, fixup_err_to_string, InferCtxt};
 
 use std::rc::Rc;
@@ -470,7 +469,7 @@ 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);
 

src/librustc/middle/traits/object_safety.rs

@@ -23,7 +23,7 @@ use super::elaborate_predicates;
 use middle::def_id::DefId;
 use middle::subst::{self, SelfSpace, TypeSpace};
 use middle::traits;
-use middle::ty::{self, HasTypeFlags, ToPolyTraitRef, Ty};
+use middle::ty::{self, ToPolyTraitRef, Ty, TypeFoldable};
 use std::rc::Rc;
 use syntax::ast;
 

src/librustc/middle/traits/project.rs

@@ -23,7 +23,7 @@ use super::util;
 
 use middle::infer::{self, TypeOrigin};
 use middle::subst::Subst;
-use middle::ty::{self, ToPredicate, RegionEscape, HasTypeFlags, ToPolyTraitRef, Ty};
+use middle::ty::{self, ToPredicate, ToPolyTraitRef, Ty};
 use middle::ty::fold::{TypeFoldable, TypeFolder};
 use syntax::parse::token;
 use util::common::FN_OUTPUT_NAME;
@@ -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.super_fold_with(self);
         match ty.sty {
             ty::TyProjection(ref data) if !data.has_escaping_regions() => { // (*)
 

src/librustc/middle/traits/select.rs

@@ -39,9 +39,8 @@ use middle::def_id::DefId;
 use middle::infer;
 use middle::infer::{InferCtxt, TypeFreshener, TypeOrigin};
 use middle::subst::{Subst, Substs, TypeSpace};
-use middle::ty::{self, ToPredicate, RegionEscape, ToPolyTraitRef, Ty, HasTypeFlags};
+use middle::ty::{self, ToPredicate, ToPolyTraitRef, Ty, TypeFoldable};
 use middle::ty::fast_reject;
-use middle::ty::fold::TypeFoldable;
 use middle::ty::relate::TypeRelation;
 
 use std::cell::RefCell;
@@ -965,7 +964,7 @@ 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()
             }
         }
     }