Check constness of default args

Check constness of default args

BUG= http://code.google.com/p/dart/issues/detail?id=635

Committed: https://code.google.com/p/dart/source/detail?r=2051

[Jennifer Messerly, 2011-12-05 00:56:28]

lgtm

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

LGTM!

But I'd appreciate it if you could fix the error message in some future checkin.

http://codereview.chromium.org/8772070/diff/1/frog/evaluator.dart
File frog/evaluator.dart (right):

http://codereview.chromium.org/8772070/diff/1/frog/evaluator.dart#newcode63
frog/evaluator.dart:63: [List<Token> modifiers = const [], TypeReference type =
null]) {
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.

http://codereview.chromium.org/8772070/diff/1/frog/member.dart
File frog/member.dart (right):

http://codereview.chromium.org/8772070/diff/1/frog/member.dart#newcode64
frog/member.dart:64: world.error('default arguments must be constant',
value.span);
Pet peeve: 'default parameter values must be constant'

http://codereview.chromium.org/8772070/diff/1/tests/language/src/ConstOptiona...
File tests/language/src/ConstOptionalArgsNegativeTest.dart (right):

http://codereview.chromium.org/8772070/diff/1/tests/language/src/ConstOptiona...
tests/language/src/ConstOptionalArgsNegativeTest.dart:6: // should be 'const {}'
Thanks for including a test with your fix!