Review comments.

compiler/rustc_hir/src/hir.rs

@@ -2849,11 +2849,6 @@ pub enum TyKind<'hir> {
     /// Type parameters may be stored in each `PathSegment`.
     Path(QPath<'hir>),
     /// An opaque type definition itself. This is only used for `impl Trait`.
-    ///
-    /// The generic argument list contains the lifetimes (and in the future
-    /// possibly parameters) that are actually bound on the `impl Trait`.
-    ///
-    /// The last parameter specifies whether this opaque appears in a trait definition.
     OpaqueDef(&'hir OpaqueTy<'hir>),
     /// A trait object type `Bound1 + Bound2 + Bound3`
     /// where `Bound` is a trait or a lifetime.

compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs

@@ -162,7 +162,7 @@ enum Scope<'a> {
     /// `fn foo<'a>() -> impl MyTrait<'a> { ... }`
     ///
     /// HIR tells us that `'a` refer to the lifetime bound on `foo`.
-    /// However, typeck and borrowck for opaques are work based on using a new generics type.
+    /// However, typeck and borrowck for opaques work based on using a new generic type.
     /// `type MyAnonTy<'b> = impl MyTrait<'b>;`
     ///
     /// This scope collects the mapping `'a -> 'b`.

compiler/rustc_resolve/src/late.rs

@@ -841,7 +841,7 @@ impl<'ra: 'ast, 'ast, 'tcx> Visitor<'ast> for LateResolutionVisitor<'_, 'ast, 'r
                 self.r.record_partial_res(ty.id, PartialRes::new(res));
                 visit::walk_ty(self, ty)
             }
-            TyKind::ImplTrait(_, _) => {
+            TyKind::ImplTrait(..) => {
                 let candidates = self.lifetime_elision_candidates.take();
                 visit::walk_ty(self, ty);
                 self.lifetime_elision_candidates = candidates;