Implementation of null-aware operators.

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 1157 matching lines @@
   static const MessageKind ASSIGNING_METHOD = const MessageKind(
       "Cannot assign a value to a method.");
 
   static const MessageKind ASSIGNING_METHOD_IN_SUPER = const MessageKind(
       "Cannot assign a value to method '#{name}' "
       "in superclass '#{superclassName}'.");
 
   static const MessageKind ASSIGNING_TYPE = const MessageKind(
       "Cannot assign a value to a type.");
 
+  static const MessageKind IF_NULL_ASSIGNING_TYPE = const MessageKind(
+      "Cannot assign a value to a type. Note that types are never null, "
+      "so this ??= assignment has no effect.");

[Johnni Winther, 2015/05/22 12:39:49]

Maybe add a [howToFix] and an example. (We test these in
tests/compiler/dart2js/message_kind_test.dart)

[Siggi Cherem (dart-lang), 2015/05/22 19:49:54]

Done.

+
   static const MessageKind VOID_NOT_ALLOWED = const MessageKind(
       "Type 'void' can't be used here because it isn't a return type.",
       howToFix: "Try removing 'void' keyword or replace it with 'var', 'final',"
           " or a type.",
       examples: const [
           "void x; main() {}",
           "foo(void x) {} main() { foo(null); }",
       ]);
 
   static const MessageKind NULL_NOT_ALLOWED = const MessageKind(
@@ skipping 1368 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';
   }
 }