Peek past balanced parens to see if they are an expression or lambda.

tokenizer.dart

Index: tokenizer.dart
diff --git a/tokenizer.dart b/tokenizer.dart
index 394041847045f99edfe2a937ee80b365595a4a1b..00f1374d90f84add16ded953e438f9b51f4c6819 100644
--- a/tokenizer.dart
+++ b/tokenizer.dart
@@ -3,6 +3,13 @@
 // BSD-style license that can be found in the LICENSE file.
 // Generated by scripts/tokenizer_gen.py.
 
+
+/**
+ */
+interface TokenSource {
+  Token next();
+}
+
 class InterpStack {
   InterpStack next, previous;
   final int quote;
@@ -26,7 +33,7 @@ class InterpStack {
  * The base class for our tokenizer. The hand coded parts are in this file, with
  * the generated parts in the subclass Tokenizer.
  */
-class TokenizerBase extends TokenizerHelpers {
+class TokenizerBase extends TokenizerHelpers implements TokenSource {
   final SourceFile _source;
   final bool _skipWhitespace;
   String _text;