Auto merge of #79945 - jackh726:existential_trait_ref, r=nikomatsakis

Move binder for dyn to each list item

This essentially changes `ty::Binder<&'tcx List<ExistentialTraitRef>>` to `&'tcx List<ty::Binder<ExistentialTraitRef>>`.

This is a first step in moving the `dyn Trait` representation closer to Chalk, which we've talked about in `@rust-lang/wg-traits.`

r? `@nikomatsakis`

compiler/rustc_middle/src/ty/context.rs

@@ -87,7 +87,7 @@ pub struct CtxtInterners<'tcx> {
     substs: InternedSet<'tcx, InternalSubsts<'tcx>>,
     canonical_var_infos: InternedSet<'tcx, List<CanonicalVarInfo<'tcx>>>,
     region: InternedSet<'tcx, RegionKind>,
-    existential_predicates: InternedSet<'tcx, List<ExistentialPredicate<'tcx>>>,
+    poly_existential_predicates: InternedSet<'tcx, List<ty::Binder<ExistentialPredicate<'tcx>>>>,
     predicate: InternedSet<'tcx, PredicateInner<'tcx>>,
     predicates: InternedSet<'tcx, List<Predicate<'tcx>>>,
     projs: InternedSet<'tcx, List<ProjectionKind>>,
@@ -103,7 +103,7 @@ impl<'tcx> CtxtInterners<'tcx> {
             type_list: Default::default(),
             substs: Default::default(),
             region: Default::default(),
-            existential_predicates: Default::default(),
+            poly_existential_predicates: Default::default(),
             canonical_var_infos: Default::default(),
             predicate: Default::default(),
             predicates: Default::default(),
@@ -1623,7 +1623,7 @@ nop_lift! {const_; &'a Const<'a> => &'tcx Const<'tcx>}
 nop_lift! {predicate; &'a PredicateInner<'a> => &'tcx PredicateInner<'tcx>}
 
 nop_list_lift! {type_list; Ty<'a> => Ty<'tcx>}
-nop_list_lift! {existential_predicates; ExistentialPredicate<'a> => ExistentialPredicate<'tcx>}
+nop_list_lift! {poly_existential_predicates; ty::Binder<ExistentialPredicate<'a>> => ty::Binder<ExistentialPredicate<'tcx>>}
 nop_list_lift! {predicates; Predicate<'a> => Predicate<'tcx>}
 nop_list_lift! {canonical_var_infos; CanonicalVarInfo<'a> => CanonicalVarInfo<'tcx>}
 nop_list_lift! {projs; ProjectionKind => ProjectionKind}
@@ -2064,7 +2064,8 @@ slice_interners!(
     type_list: _intern_type_list(Ty<'tcx>),
     substs: _intern_substs(GenericArg<'tcx>),
     canonical_var_infos: _intern_canonical_var_infos(CanonicalVarInfo<'tcx>),
-    existential_predicates: _intern_existential_predicates(ExistentialPredicate<'tcx>),
+    poly_existential_predicates:
+        _intern_poly_existential_predicates(ty::Binder<ExistentialPredicate<'tcx>>),
     predicates: _intern_predicates(Predicate<'tcx>),
     projs: _intern_projs(ProjectionKind),
     place_elems: _intern_place_elems(PlaceElem<'tcx>),
@@ -2295,7 +2296,7 @@ impl<'tcx> TyCtxt<'tcx> {
     #[inline]
     pub fn mk_dynamic(
         self,
-        obj: ty::Binder<&'tcx List<ExistentialPredicate<'tcx>>>,
+        obj: &'tcx List<ty::Binder<ExistentialPredicate<'tcx>>>,
         reg: ty::Region<'tcx>,
     ) -> Ty<'tcx> {
         self.mk_ty(Dynamic(obj, reg))
@@ -2425,13 +2426,17 @@ impl<'tcx> TyCtxt<'tcx> {
         Place { local: place.local, projection: self.intern_place_elems(&projection) }
     }
 
-    pub fn intern_existential_predicates(
+    pub fn intern_poly_existential_predicates(
         self,
-        eps: &[ExistentialPredicate<'tcx>],
-    ) -> &'tcx List<ExistentialPredicate<'tcx>> {
+        eps: &[ty::Binder<ExistentialPredicate<'tcx>>],
+    ) -> &'tcx List<ty::Binder<ExistentialPredicate<'tcx>>> {
         assert!(!eps.is_empty());
-        assert!(eps.array_windows().all(|[a, b]| a.stable_cmp(self, b) != Ordering::Greater));
-        self._intern_existential_predicates(eps)
+        assert!(
+            eps.array_windows()
+                .all(|[a, b]| a.skip_binder().stable_cmp(self, &b.skip_binder())
+                    != Ordering::Greater)
+        );
+        self._intern_poly_existential_predicates(eps)
     }
 
     pub fn intern_predicates(self, preds: &[Predicate<'tcx>]) -> &'tcx List<Predicate<'tcx>> {
@@ -2488,13 +2493,16 @@ impl<'tcx> TyCtxt<'tcx> {
         })
     }
 
-    pub fn mk_existential_predicates<
-        I: InternAs<[ExistentialPredicate<'tcx>], &'tcx List<ExistentialPredicate<'tcx>>>,
+    pub fn mk_poly_existential_predicates<
+        I: InternAs<
+            [ty::Binder<ExistentialPredicate<'tcx>>],
+            &'tcx List<ty::Binder<ExistentialPredicate<'tcx>>>,
+        >,
     >(
         self,
         iter: I,
     ) -> I::Output {
-        iter.intern_with(|xs| self.intern_existential_predicates(xs))
+        iter.intern_with(|xs| self.intern_poly_existential_predicates(xs))
     }
 
     pub fn mk_predicates<I: InternAs<[Predicate<'tcx>], &'tcx List<Predicate<'tcx>>>>(