[parser] improve inferred function names for async arrow functions

src/parsing/func-name-inferrer.h

Index: src/parsing/func-name-inferrer.h
diff --git a/src/parsing/func-name-inferrer.h b/src/parsing/func-name-inferrer.h
index ba38ffeb241c348ab8e285a842b08e5f12590615..1e8067eb3fabbd8db4988996834021a57f34cdb5 100644
--- a/src/parsing/func-name-inferrer.h
+++ b/src/parsing/func-name-inferrer.h
@@ -16,6 +16,8 @@ class AstString;
 class AstValueFactory;
 class FunctionLiteral;
 
+enum class InferName { Yes, No };
+
 // FuncNameInferrer is a stateful class that is used to perform name
 // inference for anonymous functions during static analysis of source code.
 // Inference is performed in cases when an anonymous function is assigned
@@ -71,6 +73,10 @@ class FuncNameInferrer : public ZoneObject {
     }
   }
 
+  int LastNameIndex() const { return this->names_stack_.length() - 1; }
+
+  void RemoveAsyncKeywordAtIndex(int index);

[Dan Ehrenberg, 2016/08/12 21:29:58]

Nit: Rather than exposing these two functions, why not just make this second
function take the index from the end of how far back it should remove the async
keyword?

[caitp, 2016/08/12 21:32:45]

1. prone to break with future parser changes, and 2. I think positive indexes
are easier to think about than negative indexes.

If people prefer that, sgtm

[Dan Ehrenberg, 2016/08/12 21:35:28]

The logic would be, how many things from the top of the stack would you want to
pop? Probably 0 or 1. I can't think of a case where you'd want to pop from the
beginning of the stack--that's not a reasonable thing to want to do here.

+
   // Infers a function name and leaves names collection state.
   void Infer() {
     DCHECK(IsOpen());