Support rest parameters in arrow functions

src/expression-classifier.h

Index: src/expression-classifier.h
diff --git a/src/expression-classifier.h b/src/expression-classifier.h
index 6edb99e8388427514f662f312c6341935150edac..b2f48edf28cb4a5af7d21a76a0eee80d3ce0cfb8 100644
--- a/src/expression-classifier.h
+++ b/src/expression-classifier.h
@@ -36,6 +36,8 @@ class ExpressionClassifier {
     StrictModeFormalParametersProduction = 1 << 4,
     StrongModeFormalParametersProduction = 1 << 5,
     ArrowFormalParametersProduction = 1 << 6,
+    // Unlike the others; see note in RecordArrowFormalParametersWithRest.
+    ArrowFormalParametersWithRestProduction = 1 << 7,

[Dmitry Lomov (no reviews), 2015/06/10 11:04:41]

I am not too happy about this irregularity. We aro no longer using the
classifier to report errors, but also to propagate information.

How about this: afaiu this bit is only used in parser, and parser can just
analyze the ASt directly to see if the last parameter is a spread operation or
not. WDYT?

[wingo, 2015/06/10 13:21:10]

Done.

 
     PatternProductions =
         (BindingPatternProduction | AssignmentPatternProduction),
@@ -73,6 +75,11 @@ class ExpressionClassifier {
     return is_valid(ArrowFormalParametersProduction);
   }
 
+  bool is_arrow_formal_parameters_with_rest() const {
+    return (invalid_productions_ & ArrowFormalParametersWithRestProduction) !=
+           0;
+  }
+
   bool is_valid_formal_parameter_list_without_duplicates() const {
     return is_valid(DistinctFormalParametersProduction);
   }
@@ -153,6 +160,14 @@ class ExpressionClassifier {
     arrow_formal_parameters_error_.arg = arg;
   }
 
+  void RecordArrowFormalParametersWithRest() {
+    // Unlike the other TargetProduction flags,
+    // ArrowFormalParametersWithRestProduction indicates the presence of a rest
+    // parameter, not the presence of an error.  It doesn't propagate out via
+    // Accumulate() either, and doesn't have an associated location.
+    invalid_productions_ |= ArrowFormalParametersWithRestProduction;
+  }
+
   void RecordDuplicateFormalParameterError(const Scanner::Location& loc) {
     if (!is_valid_formal_parameter_list_without_duplicates()) return;
     invalid_productions_ |= DistinctFormalParametersProduction;