1 files changed, 8 insertions, 1 deletions
diff --git a/src/libsyntax/feature_gate.rs b/src/libsyntax/feature_gate.rs
index 29da0fb1a27..f550e7d2a05 100644
--- a/src/libsyntax/feature_gate.rs
+++ b/src/libsyntax/feature_gate.rs
@@ -277,7 +277,10 @@ declare_features! (
     (active, cfg_target_has_atomic, "1.9.0", Some(32976)),
 
     // Allows `..` in tuple (struct) patterns
-    (active, dotdot_in_tuple_patterns, "1.10.0", Some(33627))
+    (active, dotdot_in_tuple_patterns, "1.10.0", Some(33627)),
+
+    // Allows `impl Trait` in function return types.
+    (active, conservative_impl_trait, "1.12.0", Some(34511))
 );
 
 declare_features! (
@@ -952,6 +955,10 @@ impl<'a> Visitor for PostExpansionVisitor<'a> {
             ast::TyKind::BareFn(ref bare_fn_ty) => {
                 self.check_abi(bare_fn_ty.abi, ty.span);
             }
+            ast::TyKind::ImplTrait(..) => {
+                gate_feature_post!(&self, conservative_impl_trait, ty.span,
+                                   "`impl Trait` is experimental");
+            }
             _ => {}
         }
         visit::walk_ty(self, ty)