Emit diagnostics for bad NSM implementations

pkg/compiler/lib/src/warnings.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.
 
 part of dart2js;
 
 const DONT_KNOW_HOW_TO_FIX = "Computer says no!";
 
 /**
  * The messages in this file should meet the following guide lines:
@@ skipping 2392 matching lines @@
   static const MessageKind MIRRORS_LIBRARY_NEW_EMITTER =
       const MessageKind(
           "dart:mirrors library is not supported when using the new emitter "
             "(DART_VM_OPTIONS='-Ddart2js.use.new.emitter=true')");
 
   static const MessageKind CALL_NOT_SUPPORTED_ON_NATIVE_CLASS =
       const MessageKind(
           "Non-supported 'call' member on a native class, or a "
           "subclass of a native class.");
 
+  static const MessageKind DIRECTLY_THROWING_NSM =
+      const MessageKind(
+          "This 'noSuchMethod' implementation is guaranteed to throw an "
+          "exception. The generated code will be smaller if it is "
+          "rewritten.",
+          howToFix: "Rewrite to "
+                    "'noSuchMethod(Invocation i) => super.noSuchMethod(i);'.");
+
+  static const MessageKind COMPLEX_THROWING_NSM =
+      const MessageKind(
+          "This 'noSuchMethod' implementation is guaranteed to throw an "
+          "exception. The generated code will be smaller and the compiler "
+          "will be able to perform more optimizations if it is rewritten.",
+          howToFix: "Rewrite to "
+                    "'noSuchMethod(Invocation i) => super.noSuchMethod(i);'.");
+
+  static const MessageKind COMPLEX_RETURNING_NSM =
+      const MessageKind(
+          "Overriding 'noSuchMethod' causes the compiler to generate "
+          "more code and prevents the compiler from doing some optimizations.",
+          howToFix: "Consider removing this 'noSuchMethod' implementation.");
+
   toString() => template;
 
   Message message([Map arguments = const {}, bool terse = false]) {
     return new Message(this, arguments, terse);
   }
 
   bool get hasHowToFix => howToFix != null && howToFix != DONT_KNOW_HOW_TO_FIX;
 }
 
 class Message {
@@ skipping 42 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';
   }
 }