resolve: collect trait aliases along with traits

src/librustc_resolve/lib.rs

@@ -1195,6 +1195,13 @@ impl<'a> ModuleData<'a> {
  }
  }
 
+ fn is_trait_alias(&self) -> bool {
+ match self.kind {
+ ModuleKind::Def(Def::TraitAlias(_), _) => true,
+ _ => false,
+ }
+ }
+
  fn nearest_item_scope(&'a self) -> Module<'a> {
  if self.is_trait() { self.parent.unwrap() } else { self }
  }
@@ -4369,8 +4376,10 @@ impl<'a> Resolver<'a> {
  let mut collected_traits = Vec::new();
  module.for_each_child(|name, ns, binding| {
  if ns != TypeNS { return }
- if let Def::Trait(_) = binding.def() {
- collected_traits.push((name, binding));
+ match binding.def() {
+ Def::Trait(_) |
+ Def::TraitAlias(_) => collected_traits.push((name, binding)),
+ _ => (),
  }
  });
  *traits = Some(collected_traits.into_boxed_slice());
@@ -4834,6 +4843,7 @@ impl<'a> Resolver<'a> {
  let container = match parent.kind {
  ModuleKind::Def(Def::Mod(_), _) => "module",
  ModuleKind::Def(Def::Trait(_), _) => "trait",
+ ModuleKind::Def(Def::TraitAlias(_), _) => "trait alias",
  ModuleKind::Block(..) => "block",
  _ => "enum",
  };
@@ -4862,6 +4872,7 @@ impl<'a> Resolver<'a> {
  (TypeNS, _) if old_binding.is_extern_crate() => "extern crate",
  (TypeNS, Some(module)) if module.is_normal() => "module",
  (TypeNS, Some(module)) if module.is_trait() => "trait",
+ (TypeNS, Some(module)) if module.is_trait_alias() => "trait alias",
  (TypeNS, _) => "type",
  };
 

src/test/run-pass/traits/trait-alias-import.rs

@@ -0,0 +1,23 @@
+#![feature(trait_alias)]
+
+mod inner {
+ pub trait Foo {
+ fn foo(&self);
+ }
+
+ pub struct Qux;
+
+ impl Foo for Qux {
+ fn foo(&self) {}
+ }
+
+ pub trait Bar = Foo;
+}
+
+// Import only the alias, not the `Foo` trait.
+use inner::{Bar, Qux};
+
+fn main() {
+ let q = Qux;
+ q.foo();
+}