Check for non-final field in the face of const constructors.

sdk/lib/_internal/compiler/implementation/warnings.dart

Index: sdk/lib/_internal/compiler/implementation/warnings.dart
diff --git a/sdk/lib/_internal/compiler/implementation/warnings.dart b/sdk/lib/_internal/compiler/implementation/warnings.dart
index 59055aead79bb4fed3df30f75f7db6944ff659df..6f1f93841f7de292bf694bc4901cee5c6dae614e 100644
--- a/sdk/lib/_internal/compiler/implementation/warnings.dart
+++ b/sdk/lib/_internal/compiler/implementation/warnings.dart
@@ -272,6 +272,29 @@ class MessageKind {
   static const MessageKind CONST_CALLS_NON_CONST = const MessageKind(
       'Error: "const" constructor cannot call a non-const constructor.');
 
+  static const MessageKind CONST_CONSTRUCTOR_WITH_NONFINAL_FIELDS =
+      const MessageKind(
+          "Error: Can't declare constructor 'const' on class #{className} "
+          "because the class contains non-final instance fields.",
+          howToFix: "Try making all fields final.",
+          examples: const ["""
+class C {
+  // 'a' must be declared final to allow for the const constructor.
+  var a;
+  const C(this.a);
+}
+
+main() => new C(0);"""]);
+
+  static const MessageKind CONST_CONSTRUCTOR_WITH_NONFINAL_FIELDS_FIELD =
+      const MessageKind('Info: This non-final field is blocking const '

[karlklose, 2013/09/05 12:43:42]

'prevents using const constructors'?

[Johnni Winther, 2013/09/06 06:22:41]

Done.

+                        'constructors.');
+
+  static const MessageKind CONST_CONSTRUCTOR_WITH_NONFINAL_FIELDS_CONSTRUCTOR =

[karlklose, 2013/09/05 12:43:42]

And something similar here.

[Johnni Winther, 2013/09/06 06:22:41]

Done.

+      const MessageKind('Info: This const constructor is blocked by '
+                        'non-final fields.');
+
+
   static const MessageKind INITIALIZING_FORMAL_NOT_ALLOWED = const MessageKind(
       'Error: Initializing formal parameter only allowed in generative '
       'constructor.');