[esnext] implement frontend changes for async/await proposal

src/parsing/scanner.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Features shared by parsing and pre-parsing scanners.
 
 #include "src/parsing/scanner.h"
 
 #include <stdint.h>
 
@@ skipping 231 matching lines @@
 
 Token::Value Scanner::Next() {
   if (next_.token == Token::EOS) {
     next_.location.beg_pos = current_.location.beg_pos;
     next_.location.end_pos = current_.location.end_pos;
   }
   current_ = next_;
   if (V8_UNLIKELY(next_next_.token != Token::UNINITIALIZED)) {
     next_ = next_next_;
     next_next_.token = Token::UNINITIALIZED;
+    has_line_terminator_before_next_ = has_line_terminator_after_next_;
     return current_.token;
   }
   has_line_terminator_before_next_ = false;
   has_multiline_comment_before_next_ = false;
   if (static_cast<unsigned>(c0_) <= 0x7f) {
     Token::Value token = static_cast<Token::Value>(one_char_tokens[c0_]);
     if (token != Token::ILLEGAL) {
       int pos = source_pos();
       next_.token = token;
       next_.location.beg_pos = pos;
       next_.location.end_pos = pos + 1;
       Advance();
       return current_.token;
     }
   }
   Scan();
   return current_.token;
 }
 
 
 Token::Value Scanner::PeekAhead() {
   if (next_next_.token != Token::UNINITIALIZED) {
     return next_next_.token;
   }
   TokenDesc prev = current_;
+  bool has_line_terminator_before_next =
+      has_line_terminator_before_next_ || has_multiline_comment_before_next_;
   Next();
+  has_line_terminator_after_next_ =
+      has_line_terminator_before_next_ || has_multiline_comment_before_next_;
+  has_line_terminator_before_next_ = has_line_terminator_before_next;
   Token::Value ret = next_.token;
   next_next_ = next_;
   next_ = current_;
   current_ = prev;
   return ret;
 }
 
 
 // TODO(yangguo): check whether this is actually necessary.
 static inline bool IsLittleEndianByteOrderMark(uc32 c) {
@@ skipping 841 matching lines @@
   const bool unicode = true;
   return ScanHexNumber<capture_raw, unicode>(4);
 }
 
 
 // ----------------------------------------------------------------------------
 // Keyword Matcher
 
 #define KEYWORDS(KEYWORD_GROUP, KEYWORD)                    \
   KEYWORD_GROUP('a')                                        \
+  KEYWORD("async", Token::ASYNC)                            \
   KEYWORD("await", Token::AWAIT)                            \
   KEYWORD_GROUP('b')                                        \
   KEYWORD("break", Token::BREAK)                            \
   KEYWORD_GROUP('c')                                        \
   KEYWORD("case", Token::CASE)                              \
   KEYWORD("catch", Token::CATCH)                            \
   KEYWORD("class", Token::CLASS)                            \
   KEYWORD("const", Token::CONST)                            \
   KEYWORD("continue", Token::CONTINUE)                      \
   KEYWORD_GROUP('d')                                        \
@@ skipping 538 matching lines @@
     backing_store_.Add(static_cast<uint8_t>((one_byte_length >> 7) | 0x80u));
   }
   backing_store_.Add(static_cast<uint8_t>(one_byte_length & 0x7f));
 
   backing_store_.AddBlock(bytes);
   return backing_store_.EndSequence().start();
 }
 
 }  // namespace internal
 }  // namespace v8