[es7] Implement async functions parsing

src/parser.cc

Index: src/parser.cc
diff --git a/src/parser.cc b/src/parser.cc
index f0affc27985c5e8b68f7bfbd3e94755e9cb96426..62a7468ab6f671d45bad5f95c0b7c230611c6330 100644
--- a/src/parser.cc
+++ b/src/parser.cc
@@ -927,6 +927,7 @@ Parser::Parser(ParseInfo* info)
   set_allow_strong_mode(FLAG_strong_mode);
   set_allow_legacy_const(FLAG_legacy_const);
   set_allow_harmony_do_expressions(FLAG_harmony_do_expressions);
+  set_allow_harmony_async_await(FLAG_harmony_async_await);
   for (int feature = 0; feature < v8::Isolate::kUseCounterFeatureCount;
        ++feature) {
     use_counts_[feature] = 0;
@@ -1408,6 +1409,11 @@ Statement* Parser::ParseStatementListItem(bool* ok) {
   }
 
   switch (peek()) {
+    case Token::ASYNC:
+      if (allow_harmony_async_await() && IsNextAsyncFunctionKeyword()) {
+        return ParseFunctionDeclaration(NULL, ok);
+      }
+      break;
     case Token::FUNCTION:
       return ParseFunctionDeclaration(NULL, ok);
     case Token::CLASS:
@@ -2229,12 +2235,16 @@ Statement* Parser::ParseFunctionDeclaration(
     ZoneList<const AstRawString*>* names, bool* ok) {
   // FunctionDeclaration ::
   //   'function' Identifier '(' FormalParameterListopt ')' '{' FunctionBody '}'
+  // AsyncFunctionDeclaration ::
+  //   'async' 'function' Identifier '(' FormalParameterListopt ')'
+  //      '{' FunctionBody '}'
   // GeneratorDeclaration ::
   //   'function' '*' Identifier '(' FormalParameterListopt ')'
   //      '{' FunctionBody '}'
+  bool is_async = allow_harmony_async_await() ? Check(Token::ASYNC) : false;
   Expect(Token::FUNCTION, CHECK_OK);
   int pos = position();
-  bool is_generator = Check(Token::MUL);
+  bool is_generator = is_async ? false : Check(Token::MUL);
   bool is_strict_reserved = false;
   const AstRawString* name = ParseIdentifierOrStrictReservedWord(
       &is_strict_reserved, CHECK_OK);
@@ -2243,13 +2253,19 @@ Statement* Parser::ParseFunctionDeclaration(
     fni_->Enter();
     fni_->PushEnclosingName(name);
   }
+
+  FunctionKind kind = FunctionKind::kNormalFunction;
+  if (is_generator) {
+    kind = FunctionKind::kGeneratorFunction;
+  } else if (is_async) {
+    kind = FunctionKind::kAsyncFunction;
+  }
+
   FunctionLiteral* fun = ParseFunctionLiteral(
       name, scanner()->location(),
       is_strict_reserved ? kFunctionNameIsStrictReserved
                          : kFunctionNameValidityUnknown,
-      is_generator ? FunctionKind::kGeneratorFunction
-                   : FunctionKind::kNormalFunction,
-      pos, FunctionLiteral::DECLARATION, FunctionLiteral::NORMAL_ARITY,
+      kind, pos, FunctionLiteral::DECLARATION, FunctionLiteral::NORMAL_ARITY,
       language_mode(), CHECK_OK);
   if (fni_ != NULL) fni_->Leave();
 
@@ -4818,6 +4834,7 @@ PreParser::PreParseResult Parser::ParseLazyFunctionBodyWithPreParser(
     SET_ALLOW(harmony_new_target);
     SET_ALLOW(strong_mode);
     SET_ALLOW(harmony_do_expressions);
+    SET_ALLOW(harmony_async_await);
 #undef SET_ALLOW
   }
   PreParser::PreParseResult result = reusable_preparser_->PreParseLazyFunction(