Add HAS_TY_PLACEHOLDER flag

Author: scalexm

src/librustc/infer/canonical/canonicalizer.rs

@@ -409,9 +409,13 @@ impl<'cx, 'gcx, 'tcx> Canonicalizer<'cx, 'gcx, 'tcx> {
         V: TypeFoldable<'tcx> + Lift<'gcx>,
     {
         let needs_canonical_flags = if canonicalize_region_mode.any() {
-            TypeFlags::HAS_FREE_REGIONS | TypeFlags::KEEP_IN_LOCAL_TCX
+            TypeFlags::KEEP_IN_LOCAL_TCX |
+            TypeFlags::HAS_FREE_REGIONS | // `HAS_RE_PLACEHOLDER` implies `HAS_FREE_REGIONS`
+            TypeFlags::HAS_TY_PLACEHOLDER
         } else {
-            TypeFlags::KEEP_IN_LOCAL_TCX
+            TypeFlags::KEEP_IN_LOCAL_TCX |
+            TypeFlags::HAS_RE_PLACEHOLDER |
+            TypeFlags::HAS_TY_PLACEHOLDER
         };
 
         let gcx = tcx.global_tcx();

src/librustc/ty/flags.rs

@@ -74,7 +74,6 @@ impl FlagComputation {
             &ty::Uint(_) |
             &ty::Never |
             &ty::Str |
-            &ty::Placeholder(..) |
             &ty::Foreign(..) => {
             }
 
@@ -120,6 +119,10 @@ impl FlagComputation {
                 self.add_binder(bound_ty.index);
             }
 
+            &ty::Placeholder(..) => {
+                self.add_flags(TypeFlags::HAS_TY_PLACEHOLDER);
+            }
+
             &ty::Infer(infer) => {
                 self.add_flags(TypeFlags::HAS_FREE_LOCAL_NAMES); // it might, right?
                 self.add_flags(TypeFlags::HAS_TY_INFER);

src/librustc/ty/fold.rs

@@ -103,7 +103,7 @@ pub trait TypeFoldable<'tcx>: fmt::Debug + Clone {
         self.has_type_flags(TypeFlags::HAS_TY_INFER | TypeFlags::HAS_RE_INFER)
     }
     fn has_placeholders(&self) -> bool {
-        self.has_type_flags(TypeFlags::HAS_RE_PLACEHOLDER)
+        self.has_type_flags(TypeFlags::HAS_RE_PLACEHOLDER | TypeFlags::HAS_TY_PLACEHOLDER)
     }
     fn needs_subst(&self) -> bool {
         self.has_type_flags(TypeFlags::NEEDS_SUBST)

src/librustc/ty/mod.rs

@@ -467,6 +467,8 @@ bitflags! {
         /// if a global bound is safe to evaluate.
         const HAS_RE_LATE_BOUND = 1 << 13;
 
+        const HAS_TY_PLACEHOLDER = 1 << 14;
+
         const NEEDS_SUBST        = TypeFlags::HAS_PARAMS.bits |
                                    TypeFlags::HAS_SELF.bits |
                                    TypeFlags::HAS_RE_EARLY_BOUND.bits;
@@ -486,7 +488,8 @@ bitflags! {
                                   TypeFlags::HAS_TY_CLOSURE.bits |
                                   TypeFlags::HAS_FREE_LOCAL_NAMES.bits |
                                   TypeFlags::KEEP_IN_LOCAL_TCX.bits |
-                                  TypeFlags::HAS_RE_LATE_BOUND.bits;
+                                  TypeFlags::HAS_RE_LATE_BOUND.bits |
+                                  TypeFlags::HAS_TY_PLACEHOLDER.bits;
     }
 }