Instantiate all bound vars existentially

5 files changed, 29 insertions, 30 deletions

diff --git a/src/librustc/infer/canonical/substitute.rs b/src/librustc/infer/canonical/substitute.rs
index b8c1ed236c0..70ce5d0d8dc 100644
--- a/src/librustc/infer/canonical/substitute.rs
+++ b/src/librustc/infer/canonical/substitute.rs
@@ -80,6 +80,6 @@ where
             }
         };
 
-        tcx.replace_escaping_bound_vars(value, fld_r, fld_t)
+        tcx.replace_escaping_bound_vars(value, fld_r, fld_t).0
     }
 }
diff --git a/src/librustc/infer/higher_ranked/mod.rs b/src/librustc/infer/higher_ranked/mod.rs
index 3e08a4e021a..642382bcf0f 100644
--- a/src/librustc/infer/higher_ranked/mod.rs
+++ b/src/librustc/infer/higher_ranked/mod.rs
@@ -59,11 +59,11 @@ impl<'a, 'gcx, 'tcx> CombineFields<'a, 'gcx, 'tcx> {
             // with a fresh region variable. These region variables --
             // but no other pre-existing region variables -- can name
             // the placeholders.
-            let (a_prime, _) =
-                self.infcx.replace_late_bound_regions_with_fresh_var(
-                    span,
-                    HigherRankedType,
-                    a);
+            let (a_prime, _) = self.infcx.replace_bound_vars_with_fresh_vars(
+                span,
+                HigherRankedType,
+                a
+            );
 
             debug!("a_prime={:?}", a_prime);
             debug!("b_prime={:?}", b_prime);
diff --git a/src/librustc/infer/mod.rs b/src/librustc/infer/mod.rs
index f5513acecf9..4ddf47c88dd 100644
--- a/src/librustc/infer/mod.rs
+++ b/src/librustc/infer/mod.rs
@@ -1328,18 +1328,18 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
         self.report_and_explain_type_error(trace, &err)
     }
 
-    pub fn replace_late_bound_regions_with_fresh_var<T>(
+    pub fn replace_bound_vars_with_fresh_vars<T>(
         &self,
         span: Span,
         lbrct: LateBoundRegionConversionTime,
-        value: &ty::Binder<T>,
+        value: &ty::Binder<T>
     ) -> (T, BTreeMap<ty::BoundRegion, ty::Region<'tcx>>)
     where
-        T: TypeFoldable<'tcx>,
+        T: TypeFoldable<'tcx>
     {
-        self.tcx.replace_late_bound_regions(value, |br| {
-            self.next_region_var(LateBoundRegion(span, br, lbrct))
-        })
+        let fld_r = |br| self.next_region_var(LateBoundRegion(span, br, lbrct));
+        let fld_t = |_| self.next_ty_var(TypeVariableOrigin::MiscVariable(span));
+        self.tcx.replace_bound_vars(value, fld_r, fld_t)
     }
 
     /// Given a higher-ranked projection predicate like:
diff --git a/src/librustc/traits/error_reporting.rs b/src/librustc/traits/error_reporting.rs
index fbada789956..2761a954cea 100644
--- a/src/librustc/traits/error_reporting.rs
+++ b/src/librustc/traits/error_reporting.rs
@@ -212,10 +212,11 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
             // cause I have no idea for a good error message.
             if let ty::Predicate::Projection(ref data) = predicate {
                 let mut selcx = SelectionContext::new(self);
-                let (data, _) = self.replace_late_bound_regions_with_fresh_var(
+                let (data, _) = self.replace_bound_vars_with_fresh_vars(
                     obligation.cause.span,
                     infer::LateBoundRegionConversionTime::HigherRankedType,
-                    data);
+                    data
+                );
                 let mut obligations = vec![];
                 let normalized_ty = super::normalize_projection_type(
                     &mut selcx,
diff --git a/src/librustc/ty/fold.rs b/src/librustc/ty/fold.rs
index ffa4380a5d6..a897afa0ca6 100644
--- a/src/librustc/ty/fold.rs
+++ b/src/librustc/ty/fold.rs
@@ -520,22 +520,14 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     pub fn replace_late_bound_regions<T, F>(
         self,
         value: &Binder<T>,
-        mut fld_r: F
+        fld_r: F
     ) -> (T, BTreeMap<ty::BoundRegion, ty::Region<'tcx>>)
         where F: FnMut(ty::BoundRegion) -> ty::Region<'tcx>,
               T: TypeFoldable<'tcx>
     {
-        let mut map = BTreeMap::new();
-        let mut real_fldr = |br| {
-            *map.entry(br).or_insert_with(|| fld_r(br))
-        };
-
         // identity for bound types
-        let mut fld_t = |bound_ty| self.mk_ty(ty::Bound(bound_ty));
-
-        let mut replacer = BoundVarReplacer::new(self, &mut real_fldr, &mut fld_t);
-        let result = value.skip_binder().fold_with(&mut replacer);
-        (result, map)
+        let fld_t = |bound_ty| self.mk_ty(ty::Bound(bound_ty));
+        self.replace_escaping_bound_vars(value.skip_binder(), fld_r, fld_t)
     }
 
     /// Replace all escaping bound vars. The `fld_r` closure replaces escaping
@@ -545,17 +537,23 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         value: &T,
         mut fld_r: F,
         mut fld_t: G
-    ) -> T
+    ) -> (T, BTreeMap<ty::BoundRegion, ty::Region<'tcx>>)
         where F: FnMut(ty::BoundRegion) -> ty::Region<'tcx>,
               G: FnMut(ty::BoundTy) -> ty::Ty<'tcx>,
               T: TypeFoldable<'tcx>
     {
+        let mut map = BTreeMap::new();
+
         if !value.has_escaping_bound_vars() {
-            value.clone()
+            (value.clone(), map)
         } else {
-            let mut replacer = BoundVarReplacer::new(self, &mut fld_r, &mut fld_t);
+            let mut real_fld_r = |br| {
+                *map.entry(br).or_insert_with(|| fld_r(br))
+            };
+
+            let mut replacer = BoundVarReplacer::new(self, &mut real_fld_r, &mut fld_t);
             let result = value.fold_with(&mut replacer);
-            result
+            (result, map)
         }
     }
 
@@ -567,7 +565,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         value: &Binder<T>,
         fld_r: F,
         fld_t: G
-    ) -> T
+    ) -> (T, BTreeMap<ty::BoundRegion, ty::Region<'tcx>>)
         where F: FnMut(ty::BoundRegion) -> ty::Region<'tcx>,
               G: FnMut(ty::BoundTy) -> ty::Ty<'tcx>,
               T: TypeFoldable<'tcx>