Don't include parameter names in types, don't use Unicode arrow.

pkg/front_end/testcases/inference/block_bodied_lambdas_infer_bottom_async.dart

 // Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /*@testedFeatures=inference*/
 library test;
 
 import 'dart:async';
 
 main() async {
-  var /*@type=() → Future<Null>*/ f = /*@returnType=Future<Null>*/ () async {
+  var /*@type=() -> Future<Null>*/ f = /*@returnType=Future<Null>*/ () async {
     return null;
   };
   Future y = /*@promotedType=none*/ f();
   Future<String> z = /*@promotedType=none*/ f();
   String s = await /*@promotedType=none*/ f();
 }