1 files changed, 7 insertions, 0 deletions
diff --git a/src/libsyntax/feature_gate.rs b/src/libsyntax/feature_gate.rs
index f186aff6d36..862c52dc4bd 100644
--- a/src/libsyntax/feature_gate.rs
+++ b/src/libsyntax/feature_gate.rs
@@ -233,6 +233,9 @@ const KNOWN_FEATURES: &'static [(&'static str, &'static str, Option<u32>, Status
 
     // Allows `#[deprecated]` attribute
     ("deprecated", "1.6.0", Some(29935), Active),
+
+    // allow using type ascription in expressions
+    ("type_ascription", "1.6.0", Some(23416), Active),
 ];
 // (changing above list without updating src/doc/reference.md makes @cmr sad)
 
@@ -960,6 +963,10 @@ impl<'a, 'v> Visitor<'v> for PostExpansionVisitor<'a> {
                                   "box expression syntax is experimental; \
                                    you can call `Box::new` instead.");
             }
+            ast::ExprType(..) => {
+                self.gate_feature("type_ascription", e.span,
+                                  "type ascription is experimental");
+            }
             _ => {}
         }
         visit::walk_expr(self, e);