Report compile-time error if using `this` implicitly in initializers

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 947141959a095a6b27787864827c1475335dfa7e..fed7def045ddd3db4f2cd6039f52bbc5bb568aff 100644
--- a/pkg/compiler/lib/src/warnings.dart
+++ b/pkg/compiler/lib/src/warnings.dart
@@ -155,6 +155,10 @@ class MessageKind {
   static const MessageKind CANNOT_RESOLVE = const MessageKind(
       "Cannot resolve '#{name}'.");
 
+  static const MessageKind CANNOT_RESOLVE_IN_INITIALIZER = const MessageKind(
+      "Cannot resolve '#{name}'. It would be implicitly looked up on this "
+      "instance, but instances are not available in initializers.");

[Johnni Winther, 2015/04/12 11:10:45]

If you add [howToFix] and [examples] we will automatically test that the example
causes the correct warning/error. See CANNOT_RESOLVE_CONSTRUCTOR_FOR_IMPLICIT
for an example. 

[Siggi Cherem (dart-lang), 2015/04/13 16:40:24]

Nice, Done.

+
   static const MessageKind CANNOT_RESOLVE_CONSTRUCTOR = const MessageKind(
       "Cannot resolve constructor '#{constructorName}'.");