Add compile-time errors for enums.

BUG=
R=floitsch@google.com

Review URL: https://codereview.chromium.org//709603003

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@41663 260f80e4-7a28-3924-810f-c04153c831b5
Add more double-parsing tests.

I was looking at double parsing, and wanted more tests for myself anyway.

R=floitsch@google.com

Review URL: https://codereview.chromium.org//712603002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@41664 260f80e4-7a28-3924-810f-c04153c831b5