[async functions] Disallow 'await' in arrow params inside async functions

src/parsing/parser-base.h

Index: src/parsing/parser-base.h
diff --git a/src/parsing/parser-base.h b/src/parsing/parser-base.h
index 0a2bf4e45a045c2146c90f6ebcf90cdfa58070f8..c5b1d28fa9743d734c219a6f13101c4b9d6d2bdf 100644
--- a/src/parsing/parser-base.h
+++ b/src/parsing/parser-base.h
@@ -933,16 +933,8 @@ class ParserBase : public Traits {
 
   void ValidateBindingPattern(const ExpressionClassifier* classifier,
                               bool* ok) {
-    if (!classifier->is_valid_binding_pattern() ||

[caitp, 2016/08/19 23:04:34]

If this passes tests, it looks great. At some point, this was definitely needed
to make `var { ... await ... }` / var [ ... await ... ]` throw within async
functions. Maybe that's not true anymore.

I guess there's no reason the normal BindingPattern handler can't do this.

[adamk, 2016/08/19 23:07:42]

Yeah, that was exactly my thinking (and it seems to be true; I still need the
call to RecordBindingPatternError, it just doesn't have to be separate from
other binding pattern errors).

The same may actually be true of ExpressionError vs CoverInitializedNameError,
see discussion in gsathya's https://codereview.chromium.org/2255353002/.

Some day I'll understand all the uses of ExpressionClassifier :)

-        !classifier->is_valid_async_binding_pattern()) {
-      const Scanner::Location& a = classifier->binding_pattern_error().location;
-      const Scanner::Location& b =
-          classifier->async_binding_pattern_error().location;
-      if (a.beg_pos < 0 || (b.beg_pos >= 0 && a.beg_pos > b.beg_pos)) {
-        ReportClassifierError(classifier->async_binding_pattern_error());
-      } else {
-        ReportClassifierError(classifier->binding_pattern_error());
-      }
+    if (!classifier->is_valid_binding_pattern()) {
+      ReportClassifierError(classifier->binding_pattern_error());
       *ok = false;
     }
   }
@@ -2788,12 +2780,10 @@ ParserBase<Traits>::ParseUnaryExpression(ExpressionClassifier* classifier,
         Next();
         IdentifierT name = this->GetSymbol(scanner());
 
-        // Possibly async arrow formals --- record ExpressionError just in case.
-        ExpressionUnexpectedToken(classifier);
-        classifier->RecordAsyncBindingPatternError(
+        classifier->RecordBindingPatternError(
             Scanner::Location(beg_pos, scanner()->location().end_pos),
             MessageTemplate::kAwaitBindingIdentifier);
-        classifier->RecordAsyncArrowFormalParametersError(
+        classifier->RecordArrowFormalParametersError(

[caitp, 2016/08/19 23:04:34]

good find!

             Scanner::Location(beg_pos, scanner()->location().end_pos),
             MessageTemplate::kAwaitBindingIdentifier);