Check constness of default args

frog/evaluator.dart

Index: frog/evaluator.dart
diff --git a/frog/evaluator.dart b/frog/evaluator.dart
index 4ff169f94c77e8c0dd44d1c0cddd610a4ecb6246..085c4e1dcb5aaba7674036cf5ac0d6a5c9da653f 100644
--- a/frog/evaluator.dart
+++ b/frog/evaluator.dart
@@ -59,8 +59,8 @@ class Evaluator {
     _lib.resolve();
   }
 
-  void _ensureVariableDefined(Identifier name, [List<Token> modifiers = [],
-      TypeReference type = null]) {
+  void _ensureVariableDefined(Identifier name,
+      [List<Token> modifiers = const [], TypeReference type = null]) {

[jimhug, 2011/12/06 16:23:39]

This is really cool!  This particular code is a notorious source of bugs in
Python programs because no one can remember when the list is initialized.  As a
result, the rule in Python is - never use a list as a default argument value -
even though that is never enforced.  The fact that your change caught this issue
and also let us fix it by just adding const to the list says something excellent
about this feature in the dart language.

     var member = _lib.topType.getMember(name.name);
     if (member is FieldMember || member is PropertyMember) return;
     _removeMember(name.name);