[esnext] implement frontend changes for async/await proposal

src/parsing/preparser.h

Index: src/parsing/preparser.h
diff --git a/src/parsing/preparser.h b/src/parsing/preparser.h
index 9e57442daf750fed05f09dc2e70c0993b84ebb4e..dda14af1ec027771ba09776fa300e5744c0ebf3e 100644
--- a/src/parsing/preparser.h
+++ b/src/parsing/preparser.h
@@ -58,6 +58,9 @@ class PreParserIdentifier {
   static PreParserIdentifier Enum() {
     return PreParserIdentifier(kEnumIdentifier);
   }
+  static PreParserIdentifier Async() {
+    return PreParserIdentifier(kAsyncIdentifier);
+  }
   static PreParserIdentifier Await() {
     return PreParserIdentifier(kAwaitIdentifier);
   }
@@ -71,6 +74,11 @@ class PreParserIdentifier {
   bool IsPrototype() const { return type_ == kPrototypeIdentifier; }
   bool IsConstructor() const { return type_ == kConstructorIdentifier; }
   bool IsEnum() const { return type_ == kEnumIdentifier; }
+  bool IsFutureReserved() const {
+    // TODO(caitp): include `kAwaitIdentifier` when parsing a Module
+    return type_ == kFutureReservedIdentifier;
+  }
+  bool IsAsync() const { return type_ == kAsyncIdentifier; }
   bool IsAwait() const { return type_ == kAwaitIdentifier; }
   bool IsFutureStrictReserved() const {
     return type_ == kFutureStrictReservedIdentifier ||
@@ -100,6 +108,7 @@ class PreParserIdentifier {
     kPrototypeIdentifier,
     kConstructorIdentifier,
     kEnumIdentifier,
+    kAsyncIdentifier,
     kAwaitIdentifier
   };
 
@@ -606,6 +615,14 @@ class PreParserTraits {
     return identifier.IsArguments();
   }
 
+  static bool IsAsync(PreParserIdentifier identifier) {
+    return identifier.IsAsync();
+  }
+
+  static bool IsAwait(PreParserIdentifier identifier) {
+    return identifier.IsAwait();
+  }
+
   static bool IsEvalOrArguments(PreParserIdentifier identifier) {
     return identifier.IsEvalOrArguments();
   }
@@ -841,6 +858,8 @@ class PreParserTraits {
       PreParserExpression expression, const Scanner::Location& params_loc,
       Scanner::Location* duplicate_loc, bool* ok);
 
+  V8_INLINE PreParserExpression ParseAsyncFunctionExpression(bool* ok);
+
   void ReindexLiterals(const PreParserFormalParameters& paramaters) {}
 
   struct TemplateLiteralState {};
@@ -913,6 +932,11 @@ class PreParserTraits {
                                            PreParserExpressionList args,
                                            int pos);
 
+  inline PreParserExpression ExpressionListToExpression(
+      PreParserExpressionList args) {
+    return PreParserExpression::Default();

[Dan Ehrenberg, 2016/05/05 01:14:40]

When do you accumulate these to a classifier/validate arrow function formal
parameters/ban await?

[caitp (gmail), 2016/05/05 01:36:57]

The main use of this is to be able to translate `async(FormalParameters) => ...`
into arrow formal parameters --- but classifier errors are recorded during
ParseArguments(), AFAIK if we see it is actually an arrow function, we report
the error.

+  }
+
   inline void RewriteDestructuringAssignments() {}
 
   inline PreParserExpression RewriteExponentiation(PreParserExpression left,
@@ -936,6 +960,9 @@ class PreParserTraits {
   inline void RewriteNonPattern(Type::ExpressionClassifier* classifier,
                                 bool* ok);
 
+  inline PreParserExpression RewriteAwaitExpression(PreParserExpression value,
+                                                    int pos);
+
   V8_INLINE Zone* zone() const;
   V8_INLINE ZoneList<PreParserExpression>* GetNonPatternList() const;
 
@@ -1054,6 +1081,8 @@ class PreParser : public ParserBase<PreParserTraits> {
   Statement ParseHoistableDeclaration(bool* ok);
   Statement ParseHoistableDeclaration(int pos, bool is_generator, bool* ok);
   Statement ParseFunctionDeclaration(bool* ok);
+  Statement ParseAsyncFunctionDeclaration(bool* ok);
+  Expression ParseAsyncFunctionExpression(bool* ok);
   Statement ParseClassDeclaration(bool* ok);
   Statement ParseBlock(bool* ok);
   Statement ParseVariableStatement(VariableDeclarationContext var_context,
@@ -1142,6 +1171,9 @@ void PreParserTraits::ParseArrowFunctionFormalParameterList(
   // lists that are too long.
 }
 
+PreParserExpression PreParserTraits::ParseAsyncFunctionExpression(bool* ok) {
+  return pre_parser_->ParseAsyncFunctionExpression(ok);
+}
 
 PreParserExpression PreParserTraits::ParseDoExpression(bool* ok) {
   return pre_parser_->ParseDoExpression(ok);
@@ -1153,6 +1185,10 @@ void PreParserTraits::RewriteNonPattern(Type::ExpressionClassifier* classifier,
   pre_parser_->ValidateExpression(classifier, ok);
 }
 
+PreParserExpression PreParserTraits::RewriteAwaitExpression(
+    PreParserExpression value, int pos) {
+  return value;
+}
 
 Zone* PreParserTraits::zone() const {
   return pre_parser_->function_state_->scope()->zone();