Downgrade ProjectionTy's TraitRef to its substs

Addresses the second part of #42171 by removing the `TraitRef` from
`ProjectionTy`, and directly storing its `Substs`.

Closes #42171.

Author: tbg

src/librustc/ich/impls_ty.rs

@@ -187,7 +187,7 @@ for ty::OutlivesPredicate<A, B>
 }
 
 impl_stable_hash_for!(struct ty::ProjectionPredicate<'tcx> { projection_ty, ty });
-impl_stable_hash_for!(struct ty::ProjectionTy<'tcx> { trait_ref, item_def_id });
+impl_stable_hash_for!(struct ty::ProjectionTy<'tcx> { substs, item_def_id });
 
 
 impl<'a, 'gcx, 'tcx> HashStable<StableHashingContext<'a, 'gcx, 'tcx>> for ty::Predicate<'tcx> {
@@ -599,8 +599,8 @@ impl_stable_hash_for!(struct ty::ExistentialTraitRef<'tcx> {
 });
 
 impl_stable_hash_for!(struct ty::ExistentialProjection<'tcx> {
-    trait_ref,
-    item_name,
+    item_def_id,
+    substs,
     ty
 });
 

src/librustc/infer/mod.rs

@@ -274,7 +274,7 @@ pub enum LateBoundRegionConversionTime {
     HigherRankedType,
 
     /// when projecting an associated type
-    AssocTypeProjection(ast::Name),
+    AssocTypeProjection(ast::Name), // FIXME(tschottdorf): should contain DefId, not Name
 }
 
 /// Reasons to create a region inference variable
@@ -1277,14 +1277,13 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                                            match_b: ty::TraitRef<'tcx>)
                                            -> InferResult<'tcx, HrMatchResult<Ty<'tcx>>>
     {
+        let match_pair = match_a.map_bound(|p| (p.projection_ty.trait_ref(self.tcx), p.ty));
         let span = cause.span;
-        let match_trait_ref = match_a.skip_binder().projection_ty.trait_ref;
         let trace = TypeTrace {
             cause,
-            values: TraitRefs(ExpectedFound::new(true, match_trait_ref, match_b))
+            values: TraitRefs(ExpectedFound::new(true, match_pair.skip_binder().0, match_b))
         };
 
-        let match_pair = match_a.map_bound(|p| (p.projection_ty.trait_ref, p.ty));
         let mut combine = self.combine_fields(trace, param_env);
         let result = combine.higher_ranked_match(span, &match_pair, &match_b, true)?;
         Ok(InferOk { value: result, obligations: combine.obligations })

src/librustc/infer/region_inference/mod.rs

@@ -1550,8 +1550,7 @@ impl<'a, 'gcx, 'tcx> GenericKind<'tcx> {
     pub fn to_ty(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Ty<'tcx> {
         match *self {
             GenericKind::Param(ref p) => p.to_ty(tcx),
-            GenericKind::Projection(ref p) => tcx.mk_projection(
-                p.trait_ref.clone(), p.item_name(tcx)),
+            GenericKind::Projection(ref p) => tcx.mk_projection(p.item_def_id, p.substs),
         }
     }
 }

src/librustc/traits/fulfill.rs

@@ -470,8 +470,9 @@ fn process_predicate<'a, 'gcx, 'tcx>(
             let project_obligation = obligation.with(data.clone());
             match project::poly_project_and_unify_type(selcx, &project_obligation) {
                 Ok(None) => {
+                    let tcx = selcx.tcx();
                     pending_obligation.stalled_on =
-                        trait_ref_type_vars(selcx, data.to_poly_trait_ref());
+                        trait_ref_type_vars(selcx, data.to_poly_trait_ref(tcx));
                     Ok(None)
                 }
                 Ok(v) => Ok(v),

src/librustc/traits/object_safety.rs

@@ -354,7 +354,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
                     // direct equality here because all of these types
                     // are part of the formal parameter listing, and
                     // hence there should be no inference variables.
-                    let projection_trait_ref = ty::Binder(data.trait_ref.clone());
+                    let projection_trait_ref = ty::Binder(data.trait_ref(self));
                     let is_supertrait_of_current_trait =
                         supertraits.as_ref().unwrap().contains(&projection_trait_ref);
 

src/librustc/traits/project.rs

@@ -365,9 +365,7 @@ pub fn normalize_projection_type<'a, 'b, 'gcx, 'tcx>(
             // information is available.
 
             let tcx = selcx.infcx().tcx;
-            let def_id = tcx.associated_items(projection_ty.trait_ref.def_id).find(|i|
-                i.name == projection_ty.item_name(tcx) && i.kind == ty::AssociatedKind::Type
-            ).map(|i| i.def_id).unwrap();
+            let def_id = projection_ty.item_def_id;
             let ty_var = selcx.infcx().next_ty_var(
                 TypeVariableOrigin::NormalizeProjectionType(tcx.def_span(def_id)));
             let projection = ty::Binder(ty::ProjectionPredicate {
@@ -447,8 +445,8 @@ fn opt_normalize_projection_type<'a, 'b, 'gcx, 'tcx>(
             // normalization. In that case, I think we will want this code:
             //
             // ```
-            // let ty = selcx.tcx().mk_projection(projection_ty.trait_ref,
-            //                                    projection_ty.item_name(tcx);
+            // let ty = selcx.tcx().mk_projection(projection_ty.item_def_id,
+            //                                    projection_ty.substs;
             // return Some(NormalizedTy { value: v, obligations: vec![] });
             // ```
 
@@ -585,15 +583,13 @@ fn normalize_to_error<'a, 'gcx, 'tcx>(selcx: &mut SelectionContext<'a, 'gcx, 'tc
                                       depth: usize)
                                       -> NormalizedTy<'tcx>
 {
-    let trait_ref = projection_ty.trait_ref.to_poly_trait_ref();
+    let trait_ref = projection_ty.trait_ref(selcx.tcx()).to_poly_trait_ref();
     let trait_obligation = Obligation { cause,
                                         recursion_depth: depth,
                                         param_env,
                                         predicate: trait_ref.to_predicate() };
     let tcx = selcx.infcx().tcx;
-    let def_id = tcx.associated_items(projection_ty.trait_ref.def_id).find(|i|
-        i.name == projection_ty.item_name(tcx) && i.kind == ty::AssociatedKind::Type
-    ).map(|i| i.def_id).unwrap();
+    let def_id = projection_ty.item_def_id;
     let new_value = selcx.infcx().next_ty_var(
         TypeVariableOrigin::NormalizeProjectionType(tcx.def_span(def_id)));
     Normalized {
@@ -654,7 +650,7 @@ fn project_type<'cx, 'gcx, 'tcx>(
         selcx.infcx().report_overflow_error(&obligation, true);
     }
 
-    let obligation_trait_ref = &obligation.predicate.trait_ref;
+    let obligation_trait_ref = &obligation.predicate.trait_ref(selcx.tcx());
 
     debug!("project: obligation_trait_ref={:?}", obligation_trait_ref);
 
@@ -743,12 +739,10 @@ fn project_type<'cx, 'gcx, 'tcx>(
                                   &obligation_trait_ref,
                                   candidate)))
         }
-        None => {
-            Ok(ProjectedTy::NoProgress(
-                selcx.tcx().mk_projection(
-                    obligation.predicate.trait_ref.clone(),
-                    obligation.predicate.item_name(selcx.tcx()))))
-        }
+        None => Ok(ProjectedTy::NoProgress(
+                    selcx.tcx().mk_projection(
+                        obligation.predicate.item_def_id,
+                        obligation.predicate.substs)))
     }
 }
 
@@ -788,10 +782,11 @@ fn assemble_candidates_from_trait_def<'cx, 'gcx, 'tcx>(
 {
     debug!("assemble_candidates_from_trait_def(..)");
 
+    let tcx = selcx.tcx();
     // Check whether the self-type is itself a projection.
     let (def_id, substs) = match obligation_trait_ref.self_ty().sty {
         ty::TyProjection(ref data) => {
-            (data.trait_ref.def_id, data.trait_ref.substs)
+            (data.trait_ref(tcx).def_id, data.substs)
         }
         ty::TyAnon(def_id, substs) => (def_id, substs),
         ty::TyInfer(ty::TyVar(_)) => {
@@ -804,9 +799,9 @@ fn assemble_candidates_from_trait_def<'cx, 'gcx, 'tcx>(
     };
 
     // If so, extract what we know from the trait and try to come up with a good answer.
-    let trait_predicates = selcx.tcx().predicates_of(def_id);
-    let bounds = trait_predicates.instantiate(selcx.tcx(), substs);
-    let bounds = elaborate_predicates(selcx.tcx(), bounds.predicates);
+    let trait_predicates = tcx.predicates_of(def_id);
+    let bounds = trait_predicates.instantiate(tcx, substs);
+    let bounds = elaborate_predicates(tcx, bounds.predicates);
     assemble_candidates_from_predicates(selcx,
                                         obligation,
                                         obligation_trait_ref,
@@ -832,12 +827,12 @@ fn assemble_candidates_from_predicates<'cx, 'gcx, 'tcx, I>(
                predicate);
         match predicate {
             ty::Predicate::Projection(ref data) => {
-                let tcx = selcx.tcx();
-                let same_name = data.item_name(tcx) == obligation.predicate.item_name(tcx);
+                let same_def_id =
+                    data.0.projection_ty.item_def_id == obligation.predicate.item_def_id;
 
-                let is_match = same_name && infcx.probe(|_| {
+                let is_match = same_def_id && infcx.probe(|_| {
                     let data_poly_trait_ref =
-                        data.to_poly_trait_ref();
+                        data.to_poly_trait_ref(infcx.tcx);
                     let obligation_poly_trait_ref =
                         obligation_trait_ref.to_poly_trait_ref();
                     infcx.at(&obligation.cause, obligation.param_env)
@@ -850,8 +845,8 @@ fn assemble_candidates_from_predicates<'cx, 'gcx, 'tcx, I>(
                 });
 
                 debug!("assemble_candidates_from_predicates: candidate={:?} \
-                                                             is_match={} same_name={}",
-                       data, is_match, same_name);
+                                                             is_match={} same_def_id={}",
+                       data, is_match, same_def_id);
 
                 if is_match {
                     candidate_set.vec.push(ctor(data.clone()));
@@ -916,9 +911,10 @@ fn assemble_candidates_from_impls<'cx, 'gcx, 'tcx>(
                 // In either case, we handle this by not adding a
                 // candidate for an impl if it contains a `default`
                 // type.
+                let item_name = selcx.tcx().associated_item(obligation.predicate.item_def_id).name;
                 let node_item = assoc_ty_def(selcx,
                                              impl_data.impl_def_id,
-                                             obligation.predicate.item_name(selcx.tcx()));
+                                             item_name);
 
                 let is_default = if node_item.node.is_from_trait() {
                     // If true, the impl inherited a `type Foo = Bar`
@@ -1091,10 +1087,9 @@ fn confirm_object_candidate<'cx, 'gcx, 'tcx>(
 
         // select only those projections that are actually projecting an
         // item with the correct name
-        let tcx = selcx.tcx();
         let env_predicates = env_predicates.filter_map(|p| match p {
             ty::Predicate::Projection(data) =>
-                if data.item_name(tcx) == obligation.predicate.item_name(tcx) {
+                if data.0.projection_ty.item_def_id == obligation.predicate.item_def_id {
                     Some(data)
                 } else {
                     None
@@ -1104,7 +1099,7 @@ fn confirm_object_candidate<'cx, 'gcx, 'tcx>(
 
         // select those with a relevant trait-ref
         let mut env_predicates = env_predicates.filter(|data| {
-            let data_poly_trait_ref = data.to_poly_trait_ref();
+            let data_poly_trait_ref = data.to_poly_trait_ref(selcx.tcx());
             let obligation_poly_trait_ref = obligation_trait_ref.to_poly_trait_ref();
             selcx.infcx().probe(|_| {
                 selcx.infcx().at(&obligation.cause, obligation.param_env)
@@ -1202,7 +1197,7 @@ fn confirm_callable_candidate<'cx, 'gcx, 'tcx>(
     // Note: we unwrap the binder here but re-create it below (1)
     let ty::Binder((trait_ref, ret_type)) =
         tcx.closure_trait_ref_and_return_type(fn_once_def_id,
-                                              obligation.predicate.trait_ref.self_ty(),
+                                              obligation.predicate.self_ty(),
                                               fn_sig,
                                               flag);
 
@@ -1227,7 +1222,7 @@ fn confirm_param_env_candidate<'cx, 'gcx, 'tcx>(
     let infcx = selcx.infcx();
     let cause = obligation.cause.clone();
     let param_env = obligation.param_env;
-    let trait_ref = obligation.predicate.trait_ref;
+    let trait_ref = obligation.predicate.trait_ref(infcx.tcx);
     match infcx.match_poly_projection_predicate(cause, param_env, poly_projection, trait_ref) {
         Ok(InferOk { value: ty_match, obligations }) => {
             Progress {
@@ -1258,7 +1253,8 @@ fn confirm_impl_candidate<'cx, 'gcx, 'tcx>(
 
     let tcx = selcx.tcx();
     let param_env = obligation.param_env;
-    let assoc_ty = assoc_ty_def(selcx, impl_def_id, obligation.predicate.item_name(tcx));
+    let assoc_ty = assoc_ty_def(selcx, impl_def_id,
+        tcx.associated_item(obligation.predicate.item_def_id).name);
 
     let ty = if !assoc_ty.item.defaultness.has_value() {
         // This means that the impl is missing a definition for the
@@ -1267,7 +1263,7 @@ fn confirm_impl_candidate<'cx, 'gcx, 'tcx>(
         // just return TyError.
         debug!("confirm_impl_candidate: no associated type {:?} for {:?}",
                assoc_ty.item.name,
-               obligation.predicate.trait_ref);
+               obligation.predicate);
         tcx.types.err
     } else {
         tcx.type_of(assoc_ty.item.def_id)

src/librustc/traits/select.rs

@@ -1335,7 +1335,8 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                skol_map);
 
         let (def_id, substs) = match skol_trait_predicate.trait_ref.self_ty().sty {
-            ty::TyProjection(ref data) => (data.trait_ref.def_id, data.trait_ref.substs),
+            ty::TyProjection(ref data) =>
+                (data.trait_ref(self.tcx()).def_id, data.substs),
             ty::TyAnon(def_id, substs) => (def_id, substs),
             _ => {
                 span_bug!(

src/librustc/traits/trans/mod.rs

@@ -203,9 +203,9 @@ impl<'gcx> DepTrackingMapConfig for ProjectionCache<'gcx> {
         let def_ids: Vec<DefId> =
             key.walk()
                .filter_map(|t| match t.sty {
-                   ty::TyAdt(adt_def, _) => Some(adt_def.did),
-                   ty::TyProjection(ref proj) => Some(proj.trait_ref.def_id),
-                   _ => None,
+                    ty::TyAdt(adt_def, _) => Some(adt_def.did),
+                    ty::TyProjection(ref proj) => Some(proj.item_def_id),
+                    _ => None,
                })
                .collect();
 

src/librustc/ty/context.rs

@@ -28,7 +28,7 @@ use mir::transform::Passes;
 use ty::subst::{Kind, Substs};
 use ty::ReprOptions;
 use traits;
-use ty::{self, TraitRef, Ty, TypeAndMut};
+use ty::{self, Ty, TypeAndMut};
 use ty::{TyS, TypeVariants, Slice};
 use ty::{AdtKind, AdtDef, ClosureSubsts, Region};
 use hir::FreevarMap;
@@ -1387,12 +1387,13 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     }
 
     pub fn mk_projection(self,
-                         trait_ref: TraitRef<'tcx>,
-                         item_name: Name)
+                         item_def_id: DefId,
+                         substs: &'tcx Substs<'tcx>)
         -> Ty<'tcx> {
-            // take a copy of substs so that we own the vectors inside
-            let inner = ProjectionTy::from_ref_and_name(self, trait_ref, item_name);
-            self.mk_ty(TyProjection(inner))
+            self.mk_ty(TyProjection(ProjectionTy {
+                item_def_id: item_def_id,
+                substs: substs,
+            }))
         }
 
     pub fn mk_closure(self,

src/librustc/ty/error.rs

@@ -14,7 +14,7 @@ use ty::{self, BoundRegion, DefIdTree, Region, Ty, TyCtxt};
 
 use std::fmt;
 use syntax::abi;
-use syntax::ast::{self, Name};
+use syntax::ast;
 use errors::DiagnosticBuilder;
 use syntax_pos::Span;
 
@@ -47,7 +47,7 @@ pub enum TypeError<'tcx> {
     Traits(ExpectedFound<DefId>),
     VariadicMismatch(ExpectedFound<bool>),
     CyclicTy,
-    ProjectionNameMismatched(ExpectedFound<Name>),
+    ProjectionMismatched(ExpectedFound<DefId>),
     ProjectionBoundsLength(ExpectedFound<usize>),
     TyParamDefaultMismatch(ExpectedFound<type_variable::Default<'tcx>>),
     ExistentialMismatch(ExpectedFound<&'tcx ty::Slice<ty::ExistentialPredicate<'tcx>>>),
@@ -154,11 +154,11 @@ impl<'tcx> fmt::Display for TypeError<'tcx> {
                        if values.expected { "variadic" } else { "non-variadic" },
                        if values.found { "variadic" } else { "non-variadic" })
             }
-            ProjectionNameMismatched(ref values) => {
+            ProjectionMismatched(ref values) => ty::tls::with(|tcx| {
                 write!(f, "expected {}, found {}",
-                       values.expected,
-                       values.found)
-            }
+                       tcx.item_path_str(values.expected),
+                       tcx.item_path_str(values.found))
+            }),
             ProjectionBoundsLength(ref values) => {
                 write!(f, "expected {} associated type bindings, found {}",
                        values.expected,