Make throw an expression

Make throw an expression

Throw e is now an expression rather than a statement. The language
spec says that throw without an expression (i.e. rethrowing the
current exception) is an expression as well. I have not implemented
this. It is rather difficult to determine at expression level whether
the keyword "throw" is followed by an expression or not. Thus,
throw without an expression is only allowed at statement level.

I think we should change the language spec to that effect.
Committed: https://code.google.com/p/dart/source/detail?r=12928

[regis, 2012-09-26 20:53:09]

LGTM

[siva, 2012-09-26 21:09:12]

http://codereview.chromium.org/10982051/diff/6001/tests/language/throw_expr_t...
File tests/language/throw_expr_test.dart (right):

http://codereview.chromium.org/10982051/diff/6001/tests/language/throw_expr_t...
tests/language/throw_expr_test.dart:56: }
I think the test will read much better if you changed the string to "up" instead
of "throw".

Also how about a try { throw 25 - throw 24; } catch (e) { }