Instantiate all bound vars universally

src/librustc/infer/higher_ranked/mod.rs

@@ -53,7 +53,7 @@ impl<'a, 'gcx, 'tcx> CombineFields<'a, 'gcx, 'tcx> {
             // First, we instantiate each bound region in the supertype with a
             // fresh placeholder region.
             let (b_prime, placeholder_map) =
-                self.infcx.replace_late_bound_regions_with_placeholders(b);
+                self.infcx.replace_bound_vars_with_placeholders(b);
 
             // Next, we instantiate each bound region in the subtype
             // with a fresh region variable. These region variables --
@@ -115,7 +115,7 @@ impl<'a, 'gcx, 'tcx> CombineFields<'a, 'gcx, 'tcx> {
             // First, we instantiate each bound region in the matcher
             // with a placeholder region.
             let ((a_match, a_value), placeholder_map) =
-                self.infcx.replace_late_bound_regions_with_placeholders(a_pair);
+                self.infcx.replace_bound_vars_with_placeholders(a_pair);
 
             debug!("higher_ranked_match: a_match={:?}", a_match);
             debug!("higher_ranked_match: placeholder_map={:?}", placeholder_map);
@@ -314,10 +314,10 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
         region_vars
     }
 
-    /// Replace all regions bound by `binder` with placeholder regions and
+    /// Replace all regions (resp. types) bound by `binder` with placeholder
-    /// return a map indicating which bound-region was replaced with what
+    /// regions (resp. types) and return a map indicating which bound-region
-    /// placeholder region. This is the first step of checking subtyping
+    /// was replaced with what placeholder region. This is the first step of
-    /// when higher-ranked things are involved.
+    /// checking subtyping when higher-ranked things are involved.
     ///
     /// **Important:** you must call this function from within a snapshot.
     /// Moreover, before committing the snapshot, you must eventually call
@@ -330,26 +330,37 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
     /// the [rustc guide].
     ///
     /// [rustc guide]: https://rust-lang-nursery.github.io/rustc-guide/traits/hrtb.html
-    pub fn replace_late_bound_regions_with_placeholders<T>(
+    pub fn replace_bound_vars_with_placeholders<T>(
         &self,
-        binder: &ty::Binder<T>,
+        binder: &ty::Binder<T>
     ) -> (T, PlaceholderMap<'tcx>)
     where
-        T : TypeFoldable<'tcx>,
+        T: TypeFoldable<'tcx>
     {
         let next_universe = self.create_next_universe();
 
-        let (result, map) = self.tcx.replace_late_bound_regions(binder, |br| {
+        let fld_r = |br| {
             self.tcx.mk_region(ty::RePlaceholder(ty::PlaceholderRegion {
                 universe: next_universe,
                 name: br,
             }))
-        });
+        };
 
-        debug!("replace_late_bound_regions_with_placeholders(binder={:?}, result={:?}, map={:?})",
+        let fld_t = |bound_ty: ty::BoundTy| {
-               binder,
+            self.tcx.mk_ty(ty::Placeholder(ty::PlaceholderType {
-               result,
+                universe: next_universe,
-               map);
+                name: bound_ty.var,
+            }))
+        };
+
+        let (result, map) = self.tcx.replace_bound_vars(binder, fld_r, fld_t);
+
+        debug!(
+            "replace_bound_vars_with_placeholders(binder={:?}, result={:?}, map={:?})",
+            binder,
+            result,
+            map
+        );
 
         (result, map)
     }
@@ -530,7 +541,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
 
     /// Pops the placeholder regions found in `placeholder_map` from the region
     /// inference context. Whenever you create placeholder regions via
-    /// `replace_late_bound_regions_with_placeholders`, they must be popped before you
+    /// `replace_bound_vars_with_placeholders`, they must be popped before you
     /// commit the enclosing snapshot (if you do not commit, e.g. within a
     /// probe or as a result of an error, then this is not necessary, as
     /// popping happens as part of the rollback).

src/librustc/infer/mod.rs

@@ -227,7 +227,7 @@ pub struct InferCtxt<'a, 'gcx: 'a + 'tcx, 'tcx: 'a> {
     universe: Cell<ty::UniverseIndex>,
 }
 
-/// A map returned by `replace_late_bound_regions_with_placeholders()`
+/// A map returned by `replace_bound_vars_with_placeholders()`
 /// indicating the placeholder region that each late-bound region was
 /// replaced with.
 pub type PlaceholderMap<'tcx> = BTreeMap<ty::BoundRegion, ty::Region<'tcx>>;
@@ -935,7 +935,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                     b,
                 },
                 placeholder_map,
-            ) = self.replace_late_bound_regions_with_placeholders(predicate);
+            ) = self.replace_bound_vars_with_placeholders(predicate);
 
             let cause_span = cause.span;
             let ok = self.at(cause, param_env).sub_exp(a_is_expected, a, b)?;
@@ -952,7 +952,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
     ) -> UnitResult<'tcx> {
         self.commit_if_ok(|snapshot| {
             let (ty::OutlivesPredicate(r_a, r_b), placeholder_map) =
-                self.replace_late_bound_regions_with_placeholders(predicate);
+                self.replace_bound_vars_with_placeholders(predicate);
             let origin = SubregionOrigin::from_obligation_cause(cause, || {
                 RelateRegionParamBound(cause.span)
             });

src/librustc/traits/project.rs

@@ -204,7 +204,7 @@ pub fn poly_project_and_unify_type<'cx, 'gcx, 'tcx>(
     let infcx = selcx.infcx();
     infcx.commit_if_ok(|snapshot| {
         let (placeholder_predicate, placeholder_map) =
-            infcx.replace_late_bound_regions_with_placeholders(&obligation.predicate);
+            infcx.replace_bound_vars_with_placeholders(&obligation.predicate);
 
         let skol_obligation = obligation.with(placeholder_predicate);
         let r = match project_and_unify_type(selcx, &skol_obligation) {

src/librustc/traits/select.rs

@@ -1726,7 +1726,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
         let poly_trait_predicate = self.infcx()
             .resolve_type_vars_if_possible(&obligation.predicate);
         let (skol_trait_predicate, placeholder_map) = self.infcx()
-            .replace_late_bound_regions_with_placeholders(&poly_trait_predicate);
+            .replace_bound_vars_with_placeholders(&poly_trait_predicate);
         debug!(
             "match_projection_obligation_against_definition_bounds: \
              skol_trait_predicate={:?} placeholder_map={:?}",
@@ -2685,7 +2685,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
 
                 self.in_snapshot(|this, snapshot| {
                     let (skol_ty, placeholder_map) = this.infcx()
-                        .replace_late_bound_regions_with_placeholders(&ty);
+                        .replace_bound_vars_with_placeholders(&ty);
                     let Normalized {
                         value: normalized_ty,
                         mut obligations,
@@ -2919,7 +2919,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
         let trait_obligations: Vec<PredicateObligation<'_>> = self.in_snapshot(|this, snapshot| {
             let poly_trait_ref = obligation.predicate.to_poly_trait_ref();
             let (trait_ref, placeholder_map) = this.infcx()
-                .replace_late_bound_regions_with_placeholders(&poly_trait_ref);
+                .replace_bound_vars_with_placeholders(&poly_trait_ref);
             let cause = obligation.derived_cause(ImplDerivedObligation);
             this.impl_or_trait_obligations(
                 cause,
@@ -3122,7 +3122,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
 
         self.in_snapshot(|this, snapshot| {
             let (predicate, placeholder_map) = this.infcx()
-                .replace_late_bound_regions_with_placeholders(&obligation.predicate);
+                .replace_bound_vars_with_placeholders(&obligation.predicate);
             let trait_ref = predicate.trait_ref;
             let trait_def_id = trait_ref.def_id;
             let substs = trait_ref.substs;
@@ -3585,7 +3585,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
         }
 
         let (skol_obligation, placeholder_map) = self.infcx()
-            .replace_late_bound_regions_with_placeholders(&obligation.predicate);
+            .replace_bound_vars_with_placeholders(&obligation.predicate);
         let skol_obligation_trait_ref = skol_obligation.trait_ref;
 
         let impl_substs = self.infcx