Add default impls for Send/Sync

src/libcore/marker.rs

@@ -39,6 +39,8 @@ pub unsafe trait Send : MarkerTrait {
     // empty.
 }
 
+impl Send for .. { }
+
 impl<T> !Send for *const T { }
 impl<T> !Send for *mut T { }
 impl !Send for Managed { }
@@ -203,6 +205,8 @@ pub unsafe trait Sync : MarkerTrait {
     // Empty
 }
 
+impl Sync for .. { }
+
 impl<T> !Sync for *const T { }
 impl<T> !Sync for *mut T { }
 impl !Sync for Managed { }

src/librustc/middle/ty.rs

@@ -5980,10 +5980,7 @@ pub fn item_variances(tcx: &ctxt, item_id: ast::DefId) -> Rc<ItemVariances> {
 
 pub fn trait_has_default_impl(tcx: &ctxt, trait_def_id: DefId) -> bool {
     populate_implementations_for_trait_if_necessary(tcx, trait_def_id);
-    match tcx.lang_items.to_builtin_kind(trait_def_id) {
-        Some(BoundSend) | Some(BoundSync) => true,
-        _ => tcx.traits_with_default_impls.borrow().contains_key(&trait_def_id),
-    }
+    tcx.traits_with_default_impls.borrow().contains_key(&trait_def_id)
 }
 
 /// Records a trait-to-implementation mapping.