Implementation of null-aware operators.

pkg/compiler/lib/src/warnings.dart

Index: pkg/compiler/lib/src/warnings.dart
diff --git a/pkg/compiler/lib/src/warnings.dart b/pkg/compiler/lib/src/warnings.dart
index 8977b5d9220dfd3a363dbf728a4cec8f805dcfaa..a168c31b1a8895f00ca7afc674959a702a3c1c7d 100644
--- a/pkg/compiler/lib/src/warnings.dart
+++ b/pkg/compiler/lib/src/warnings.dart
@@ -1175,6 +1175,10 @@ main() => new C();"""]);
   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',"