Handle generic parameters.

compiler/rustc_hir/src/hir.rs

@@ -2505,6 +2505,7 @@ pub struct OpaqueTy<'hir> {
     pub generics: &'hir Generics<'hir>,
     pub bounds: GenericBounds<'hir>,
     pub origin: OpaqueTyOrigin,
+    pub in_trait: bool,
 }
 
 /// From whence the opaque type came.
@@ -2518,12 +2519,6 @@ pub enum OpaqueTyOrigin {
     TyAlias,
 }
 
-/// Placeholder representation of an `impl Trait` in a trait. Since this never gets lowered into a `ty::Opaque` of its own, we just keep this as
-#[derive(Debug, HashStable_Generic)]
-pub struct ImplTraitPlaceholder<'hir> {
-    pub bounds: GenericBounds<'hir>,
-}
-
 /// The various kinds of types recognized by the compiler.
 #[derive(Debug, HashStable_Generic)]
 pub enum TyKind<'hir> {
@@ -2550,12 +2545,9 @@ pub enum TyKind<'hir> {
     ///
     /// The generic argument list contains the lifetimes (and in the future
     /// possibly parameters) that are actually bound on the `impl Trait`.
-    OpaqueDef(ItemId, &'hir [GenericArg<'hir>]),
-    /// A type that represents an `impl Trait` in a trait function. This is
-    /// not an opaque type, since it acts more like an associated type than
-    /// an opaque, and since it needs no generics since it inherits those
-    /// from the item's parent.
-    ImplTraitInTrait(ItemId),
+    ///
+    /// The last parameter specifies whether this opaque appears in a trait definition.
+    OpaqueDef(ItemId, &'hir [GenericArg<'hir>], bool),
     /// A trait object type `Bound1 + Bound2 + Bound3`
     /// where `Bound` is a trait or a lifetime.
     TraitObject(&'hir [PolyTraitRef<'hir>], &'hir Lifetime, TraitObjectSyntax),
@@ -3011,8 +3003,6 @@ pub enum ItemKind<'hir> {
     TyAlias(&'hir Ty<'hir>, &'hir Generics<'hir>),
     /// An opaque `impl Trait` type alias, e.g., `type Foo = impl Bar;`.
     OpaqueTy(OpaqueTy<'hir>),
-    /// An `impl Trait` in a trait
-    ImplTraitPlaceholder(ImplTraitPlaceholder<'hir>),
     /// An enum definition, e.g., `enum Foo<A, B> {C<A>, D<B>}`.
     Enum(EnumDef<'hir>, &'hir Generics<'hir>),
     /// A struct definition, e.g., `struct Foo<A> {x: A}`.
@@ -3081,7 +3071,6 @@ impl ItemKind<'_> {
             ItemKind::Trait(..) => "trait",
             ItemKind::TraitAlias(..) => "trait alias",
             ItemKind::Impl(..) => "implementation",
-            ItemKind::ImplTraitPlaceholder(..) => "opaque type in trait",
         }
     }
 }