Enabled Self in type aliases.

Author: Alexander Regueiro

src/librustc_resolve/lib.rs

@@ -2529,7 +2529,17 @@ impl<'a> Resolver<'a> {
         debug!("(resolving item) resolving {} ({:?})", name, item.node);
 
         match item.node {
-            ItemKind::Ty(_, ref generics) |
+            ItemKind::Ty(_, ref generics) => {
+                self.with_current_self_item(item, |this| {
+                    this.with_generic_param_rib(HasGenericParams(generics, ItemRibKind), |this| {
+                        let item_def_id = this.definitions.local_def_id(item.id);
+                        this.with_self_rib(Def::SelfTy(Some(item_def_id), None), |this| {
+                            visit::walk_item(this, item)
+                        })
+                    })
+                });
+            }
+
             ItemKind::Existential(_, ref generics) |
             ItemKind::Fn(_, _, ref generics, _) => {
                 self.with_generic_param_rib(

src/librustc_typeck/astconv.rs

@@ -1770,7 +1770,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx> + 'o {
                 tcx.mk_ty_param(index, tcx.hir().name_by_hir_id(hir_id).as_interned_str())
             }
             Res::SelfTy(Some(_), None) => {
-                // `Self` in trait.
+                // `Self` in trait or type alias.
                 assert_eq!(opt_self_ty, None);
                 self.prohibit_generics(&path.segments);
                 tcx.mk_self_type()