[dart2js] Report an error if throw is used outside of catch expression without an argument.

lib/compiler/implementation/warnings.dart

Index: lib/compiler/implementation/warnings.dart
diff --git a/lib/compiler/implementation/warnings.dart b/lib/compiler/implementation/warnings.dart
index 3c0ec5300aa8bd1231f8a0cefca979b9b3e21b78..14bd4770744d094c0ddc0d77a8b5d8cc78e1991e 100644
--- a/lib/compiler/implementation/warnings.dart
+++ b/lib/compiler/implementation/warnings.dart
@@ -116,6 +116,8 @@ class MessageKind {
       'cannot use modifiers in catch');
   static const OPTIONAL_PARAMETER_IN_CATCH = const MessageKind(
       'cannot use optional parameters in catch');
+  static const THROW_WITHOUT_EXPRESSION = const MessageKind(
+      'cannot throw without expression outside of catch block');

[ahe, 2012/10/03 09:57:39]

How about:

'cannot use re-throw outside of catch block (expression expected after "throw")'

[Roman, 2012/10/03 10:07:34]

Done.

   static const UNBOUND_LABEL = const MessageKind(
       'cannot resolve label #{1}');
   static const NO_BREAK_TARGET = const MessageKind(