Changes dart2js to warn at reified usage of method type variables.

pkg/compiler/lib/src/diagnostics/messages.dart

 // Copyright (c) 2011, 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.
 
 /**
  * The messages in this file should meet the following guide lines:
  *
  * 1. The message should be a complete sentence starting with an uppercase
  * letter, and ending with a period.
  *
@@ skipping 1137 matching lines @@
 
   m(T t) => const C<T>();
 }
 
 void main() => new C().m(null);
 """
           ]),
 
       MessageKind.TYPE_VARIABLE_FROM_METHOD_NOT_REIFIED: const MessageTemplate(
           MessageKind.TYPE_VARIABLE_FROM_METHOD_NOT_REIFIED,
-          "Method type variables are not reified.",
-          howToFix: "Try using the intended upper bound of the "
-              "type variable, or dynamic."
-// TODO(eernst): These examples should be commented in with an `options:`
-// specifying "--generic-method-syntax" and made to work; moreover, the
-// compiler/dart2js test 'generic_method_type_usage' should be transformed to
-// similar examples of the relevant `MessageKind` entries.
-//
-//        examples: const [
-//            """
-// // Method type variables are not reified, so they cannot be returned.
-// Type f<T>() => T;
-//
-// main() => f<int>();
-// """,
-//            """
-// // Method type variables are not reified, so they cannot be tested dynamically.
-// bool f<T>(Object o) => o is T;
-//
-// main() => f<int>(42);
-// """,
-//            """
-// // Method type variables are not reified, so they cannot be tested dynamically.
-// bool f<T>(Object o) => o as T;
-//
-// main() => f<int>(42);
-// """
-//    ]
-      ),
+          "Method type variables do not have a runtime value.",
+          options: const ["--generic-method-syntax"],
+          howToFix: "Try using the upper bound of the type variable, "
+              "or refactor the code to avoid needing this runtime value.",
+          examples: const [
+            """
+// Method type variables are not reified, so they cannot be returned.
+Type f<T>() => T;
+
+main() => f<int>();
+""",
+            """
+// Method type variables are not reified, so they cannot be tested dynamically.
+bool f<T>(Object o) => o is T;
+
+main() => f<int>(42);
+""",
+            """
+// Method type variables are not reified, so they cannot be tested dynamically.
+bool f<T>(Object o) => o as T;
+
+main() => f<int>(42);
+"""
+          ]),
 
       MessageKind.INVALID_TYPE_VARIABLE_BOUND: const MessageTemplate(
           MessageKind.INVALID_TYPE_VARIABLE_BOUND,
           "'#{typeArgument}' is not a subtype of bound '#{bound}' for "
           "type variable '#{typeVariable}' of type '#{thisType}'.",
           howToFix: "Try to change or remove the type argument.",
           examples: const [
             """
 class C<T extends num> {}
 
@@ skipping 2553 matching lines @@
   static String convertToString(value) {
     if (value is ErrorToken) {
       // Shouldn't happen.
       return value.assertionMessage;
     } else if (value is Token) {
       value = value.value;
     }
     return '$value';
   }
 }