[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 c803928fd8e30582acf74c3657e3f40f05660241..c61eb608293f4521ee82d411f5c7692ae804d50b 100644
--- a/src/parsing/preparser.h
+++ b/src/parsing/preparser.h
@@ -55,6 +55,12 @@ class PreParserIdentifier {
   static PreParserIdentifier Constructor() {
     return PreParserIdentifier(kConstructorIdentifier);
   }
+  static PreParserIdentifier Async() {
+    return PreParserIdentifier(kAsyncIdentifier);
+  }
+  static PreParserIdentifier Await() {
+    return PreParserIdentifier(kAwaitIdentifier);
+  }
   bool IsEval() const { return type_ == kEvalIdentifier; }
   bool IsArguments() const { return type_ == kArgumentsIdentifier; }
   bool IsEvalOrArguments() const { return IsEval() || IsArguments(); }
@@ -64,7 +70,12 @@ class PreParserIdentifier {
   bool IsYield() const { return type_ == kYieldIdentifier; }
   bool IsPrototype() const { return type_ == kPrototypeIdentifier; }
   bool IsConstructor() const { return type_ == kConstructorIdentifier; }
-  bool IsFutureReserved() const { return type_ == kFutureReservedIdentifier; }
+  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 ||
            type_ == kLetIdentifier || type_ == kStaticIdentifier ||
@@ -91,7 +102,9 @@ class PreParserIdentifier {
     kArgumentsIdentifier,
     kUndefinedIdentifier,
     kPrototypeIdentifier,
-    kConstructorIdentifier
+    kConstructorIdentifier,
+    kAsyncIdentifier,
+    kAwaitIdentifier
   };
 
   explicit PreParserIdentifier(Type type) : type_(type) {}
@@ -597,6 +610,14 @@ 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();
   }
@@ -832,6 +853,8 @@ 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 {};
@@ -900,6 +923,11 @@ class PreParserTraits {
                                            PreParserExpressionList args,
                                            int pos);
 
+  inline PreParserExpression ExpressionListToExpression(
+      PreParserExpressionList args) {
+    return PreParserExpression::Default();
+  }
+
   inline void RewriteDestructuringAssignments() {}
 
   inline PreParserExpression RewriteExponentiation(PreParserExpression left,
@@ -923,6 +951,9 @@ 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;
 
@@ -1025,6 +1056,8 @@ class PreParser : public ParserBase<PreParserTraits> {
                               bool* ok);
   Statement ParseScopedStatement(bool legacy, 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,
@@ -1110,6 +1143,9 @@ 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);
@@ -1121,6 +1157,10 @@ 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();