Generate tear-off closures dynamically.

dart/sdk/lib/_internal/compiler/implementation/scanner/parser.dart

Index: dart/sdk/lib/_internal/compiler/implementation/scanner/parser.dart
diff --git a/dart/sdk/lib/_internal/compiler/implementation/scanner/parser.dart b/dart/sdk/lib/_internal/compiler/implementation/scanner/parser.dart
index af56bf995fc049f84f205099015ccc4f17dc0fba..024175e38674d4bec6682452cd96205566198fc3 100644
--- a/dart/sdk/lib/_internal/compiler/implementation/scanner/parser.dart
+++ b/dart/sdk/lib/_internal/compiler/implementation/scanner/parser.dart
@@ -1778,7 +1778,7 @@ class Parser {
   }
 
   Token parseParenthesizedExpression(Token token) {
-    var begin = (token as BeginGroupToken);
+    var begin = token;

[kasperl, 2013/11/29 10:10:55]

var -> BeginGroupToken?

[ahe, 2013/12/06 15:57:53]

That breaks the code. We don't know that token is a BeginGroupToken until
calling expect. This change has already been submitted in a separate CL, and I
added a comment.

     token = expect('(', token);
     token = parseExpression(token);
     if (!identical(begin.endGroup, token)) {