Adjust bound tys indices in canonicalization

src/librustc/infer/canonical/canonicalizer.rs

@@ -280,6 +280,8 @@ struct Canonicalizer<'cx, 'gcx: 'tcx, 'tcx: 'cx> {
     indices: FxHashMap<Kind<'tcx>, BoundVar>,
     canonicalize_region_mode: &'cx dyn CanonicalizeRegionMode,
     needs_canonical_flags: TypeFlags,
+
+    binder_index: ty::DebruijnIndex,
 }
 
 impl<'cx, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for Canonicalizer<'cx, 'gcx, 'tcx> {
@@ -287,12 +289,24 @@ impl<'cx, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for Canonicalizer<'cx, 'gcx, 'tcx>
         self.tcx
     }
 
+    fn fold_binder<T>(&mut self, t: &ty::Binder<T>) -> ty::Binder<T>
+        where T: TypeFoldable<'tcx>
+    {
+        self.binder_index.shift_in(1);
+        let t = t.super_fold_with(self);
+        self.binder_index.shift_out(1);
+        t
+    }
+
     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
         match *r {
-            ty::ReLateBound(..) => {
-                // leave bound regions alone
+            ty::ReLateBound(index, ..) => {
+                if index >= self.binder_index {
+                    bug!("escaping late bound region during canonicalization")
+                } else {
                     r
                 }
+            }
 
             ty::ReVar(vid) => {
                 let r = self.infcx
@@ -337,8 +351,12 @@ impl<'cx, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for Canonicalizer<'cx, 'gcx, 'tcx>
                 bug!("encountered a fresh type during canonicalization")
             }
 
-            ty::Bound(_) => {
-                bug!("encountered a bound type during canonicalization")
+            ty::Bound(bound_ty) => {
+                if bound_ty.index >= self.binder_index {
+                    bug!("escaping bound type during canonicalization")
+                } else {
+                    t
+                }
             }
 
             ty::Closure(..)
@@ -422,6 +440,7 @@ impl<'cx, 'gcx, 'tcx> Canonicalizer<'cx, 'gcx, 'tcx> {
             variables: SmallVec::new(),
             query_state,
             indices: FxHashMap::default(),
+            binder_index: ty::INNERMOST,
         };
         let out_value = value.fold_with(&mut canonicalizer);
 
@@ -567,7 +586,7 @@ impl<'cx, 'gcx, 'tcx> Canonicalizer<'cx, 'gcx, 'tcx> {
                 kind: CanonicalVarKind::Ty(ty_kind),
             };
             let var = self.canonical_var(info, ty_var.into());
-            self.tcx().mk_ty(ty::Bound(BoundTy::new(ty::INNERMOST, var)))
+            self.tcx().mk_ty(ty::Bound(BoundTy::new(self.binder_index, var)))
         }
     }
 }

src/librustc/infer/canonical/query_response.rs

@@ -433,6 +433,7 @@ impl<'cx, 'gcx, 'tcx> InferCtxt<'cx, 'gcx, 'tcx> {
                 UnpackedKind::Type(result_value) => {
                     // e.g., here `result_value` might be `?0` in the example above...
                     if let ty::Bound(b) = result_value.sty {
+                        assert_eq!(b.index, ty::INNERMOST);
                         // in which case we would set `canonical_vars[0]` to `Some(?U)`.
                         opt_values[b.var] = Some(*original_value);
                     }

src/librustc/infer/canonical/substitute.rs

@@ -69,13 +69,18 @@ where
     } else if !value.has_type_flags(TypeFlags::HAS_CANONICAL_VARS) {
         value.clone()
     } else {
-        value.fold_with(&mut CanonicalVarValuesSubst { tcx, var_values })
+        value.fold_with(&mut CanonicalVarValuesSubst {
+            tcx,
+            var_values,
+            binder_index: ty::INNERMOST,
+        })
     }
 }
 
 struct CanonicalVarValuesSubst<'cx, 'gcx: 'tcx, 'tcx: 'cx> {
     tcx: TyCtxt<'cx, 'gcx, 'tcx>,
     var_values: &'cx CanonicalVarValues<'tcx>,
+    binder_index: ty::DebruijnIndex,
 }
 
 impl<'cx, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for CanonicalVarValuesSubst<'cx, 'gcx, 'tcx> {
@@ -83,13 +88,30 @@ impl<'cx, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for CanonicalVarValuesSubst<'cx, 'g
         self.tcx
     }
 
+    fn fold_binder<T>(&mut self, t: &ty::Binder<T>) -> ty::Binder<T>
+        where T: TypeFoldable<'tcx>
+    {
+        self.binder_index.shift_in(1);
+        let t = t.super_fold_with(self);
+        self.binder_index.shift_out(1);
+        t
+    }
+
     fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
         match t.sty {
             ty::Bound(b) => {
+                if b.index == self.binder_index {
                     match self.var_values.var_values[b.var].unpack() {
-                    UnpackedKind::Type(ty) => ty,
+                        UnpackedKind::Type(ty) => ty::fold::shift_vars(
+                            self.tcx,
+                            self.binder_index.index() as u32,
+                            &ty
+                        ),
                         r => bug!("{:?} is a type but value is {:?}", b, r),
                     }
+                } else {
+                    t
+                }
             }
             _ => {
                 if !t.has_type_flags(TypeFlags::HAS_CANONICAL_VARS) {

src/librustc/ty/subst.rs

@@ -556,7 +556,10 @@ impl CanonicalUserSubsts<'tcx> {
         self.value.substs.iter().zip(BoundVar::new(0)..).all(|(kind, cvar)| {
             match kind.unpack() {
                 UnpackedKind::Type(ty) => match ty.sty {
-                    ty::Bound(ref b) => cvar == b.var,
+                    ty::Bound(ref b) => {
+                        assert_eq!(b.index, ty::INNERMOST);
+                        cvar == b.var
+                    }
                     _ => false,
                 },