Introduce TyKind::Placeholder variant

Author: scalexm

src/librustc/ich/impls_ty.rs

@@ -687,6 +687,9 @@ for ty::TyKind<'gcx>
             Bound(bound_ty) => {
                 bound_ty.hash_stable(hcx, hasher);
             }
+            ty::Placeholder(placeholder_ty) => {
+                placeholder_ty.hash_stable(hcx, hasher);
+            }
             Foreign(def_id) => {
                 def_id.hash_stable(hcx, hasher);
             }

src/librustc/infer/canonical/canonicalizer.rs

@@ -380,6 +380,7 @@ impl<'cx, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for Canonicalizer<'cx, 'gcx, 'tcx>
             | ty::Never
             | ty::Tuple(..)
             | ty::Projection(..)
+            | ty::Placeholder(..)
             | ty::UnnormalizedProjection(..)
             | ty::Foreign(..)
             | ty::Param(..)

src/librustc/infer/freshen.rs

@@ -170,9 +170,6 @@ impl<'a, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for TypeFreshener<'a, 'gcx, 'tcx> {
                 t
             }
 
-            ty::Bound(..) =>
-                bug!("encountered bound ty during freshening"),
-
             ty::Generator(..) |
             ty::Bool |
             ty::Char |
@@ -200,6 +197,9 @@ impl<'a, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for TypeFreshener<'a, 'gcx, 'tcx> {
             ty::Opaque(..) => {
                 t.super_fold_with(self)
             }
+
+            ty::Placeholder(..) |
+            ty::Bound(..) => bug!("unexpected type {:?}", t),
         }
     }
 }

src/librustc/traits/coherence.rs

@@ -455,7 +455,7 @@ fn ty_is_local_constructor(ty: Ty<'_>, in_crate: InCrate) -> bool {
             false
         }
 
-        ty::Bound(..) | ty::Infer(..) => match in_crate {
+        ty::Placeholder(..) | ty::Bound(..) | ty::Infer(..) => match in_crate {
             InCrate::Local => false,
             // The inference variable might be unified with a local
             // type in that remote crate.

src/librustc/traits/error_reporting.rs

@@ -281,7 +281,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                 ty::Generator(..) => Some(18),
                 ty::Foreign(..) => Some(19),
                 ty::GeneratorWitness(..) => Some(20),
-                ty::Bound(..) | ty::Infer(..) | ty::Error => None,
+                ty::Placeholder(..) | ty::Bound(..) | ty::Infer(..) | ty::Error => None,
                 ty::UnnormalizedProjection(..) => bug!("only used with chalk-engine"),
             }
         }

src/librustc/traits/query/dropck_outlives.rs

@@ -251,6 +251,7 @@ pub fn trivial_dropck_outlives<'tcx>(tcx: TyCtxt<'_, '_, 'tcx>, ty: Ty<'tcx>) ->
         | ty::Projection(..)
         | ty::Param(_)
         | ty::Opaque(..)
+        | ty::Placeholder(..)
         | ty::Infer(_)
         | ty::Bound(..)
         | ty::Generator(..) => false,

src/librustc/traits/select.rs

@@ -2470,6 +2470,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
             ty::Infer(ty::TyVar(_)) => Ambiguous,
 
             ty::UnnormalizedProjection(..)
+            | ty::Placeholder(..)
             | ty::Bound(_)
             | ty::Infer(ty::FreshTy(_))
             | ty::Infer(ty::FreshIntTy(_))
@@ -2555,6 +2556,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
             }
 
             ty::UnnormalizedProjection(..)
+            | ty::Placeholder(..)
             | ty::Bound(_)
             | ty::Infer(ty::FreshTy(_))
             | ty::Infer(ty::FreshIntTy(_))
@@ -2594,6 +2596,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
             | ty::Char => Vec::new(),
 
             ty::UnnormalizedProjection(..)
+            | ty::Placeholder(..)
             | ty::Dynamic(..)
             | ty::Param(..)
             | ty::Foreign(..)

src/librustc/ty/context.rs

@@ -2250,7 +2250,7 @@ impl<'a, 'tcx> TyCtxt<'a, 'tcx, 'tcx> {
     pub fn print_debug_stats(self) {
         sty_debug_print!(
             self,
-            Adt, Array, Slice, RawPtr, Ref, FnDef, FnPtr,
+            Adt, Array, Slice, RawPtr, Ref, FnDef, FnPtr, Placeholder,
             Generator, GeneratorWitness, Dynamic, Closure, Tuple, Bound,
             Param, Infer, UnnormalizedProjection, Projection, Opaque, Foreign);
 

src/librustc/ty/error.rs

@@ -212,6 +212,7 @@ impl<'a, 'gcx, 'lcx, 'tcx> ty::TyS<'tcx> {
             ty::Infer(ty::TyVar(_)) => "inferred type".into(),
             ty::Infer(ty::IntVar(_)) => "integral variable".into(),
             ty::Infer(ty::FloatVar(_)) => "floating-point variable".into(),
+            ty::Placeholder(..) => "placeholder type".into(),
             ty::Bound(_) |
             ty::Infer(ty::FreshTy(_)) => "fresh type".into(),
             ty::Infer(ty::FreshIntTy(_)) => "fresh integral type".into(),

src/librustc/ty/fast_reject.rs

@@ -122,7 +122,7 @@ pub fn simplify_type<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
         ty::Foreign(def_id) => {
             Some(ForeignSimplifiedType(def_id))
         }
-        ty::Bound(..) | ty::Infer(_) | ty::Error => None,
+        ty::Placeholder(..) | ty::Bound(..) | ty::Infer(_) | ty::Error => None,
     }
 }