auto merge of #11632 : brson/rust/issue-11602, r=huonw

Author: bors

src/librustc/front/feature_gate.rs

@@ -45,6 +45,7 @@ static KNOWN_FEATURES: &'static [(&'static str, Status)] = &[
     ("link_args", Active),
     ("phase", Active),
     ("macro_registrar", Active),
+    ("log_syntax", Active),
 
     // These are used to test this portion of the compiler, they don't actually
     // mean anything
@@ -187,6 +188,11 @@ impl Visitor<()> for Context {
             self.gate_feature("asm", path.span, "inline assembly is not \
                 stable enough for use and is subject to change");
         }
+
+        else if path.segments.last().identifier == self.sess.ident_of("log_syntax") {
+            self.gate_feature("log_syntax", path.span, "`log_syntax!` is not \
+                stable enough for use and is subject to change");
+        }
     }
 
     fn visit_ty(&mut self, t: &ast::Ty, _: ()) {

src/test/compile-fail/log-syntax-gate.rs

@@ -0,0 +1,13 @@
+// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+fn main() {
+    log_syntax!() //~ ERROR `log_syntax!` is not stable enough
+}