[es7] implement exponentiation operator 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 22 matching lines @@
 void Utf16CharacterStream::ResetToBookmark() { UNREACHABLE(); }
 
 
 // ----------------------------------------------------------------------------
 // Scanner
 
 Scanner::Scanner(UnicodeCache* unicode_cache)
     : unicode_cache_(unicode_cache),
       bookmark_c0_(kNoBookmark),
       octal_pos_(Location::invalid()),
-      found_html_comment_(false) {
+      found_html_comment_(false),
+      allow_harmony_exponentiation_operator_(false) {
   bookmark_current_.literal_chars = &bookmark_current_literal_;
   bookmark_current_.raw_literal_chars = &bookmark_current_raw_literal_;
   bookmark_next_.literal_chars = &bookmark_next_literal_;
   bookmark_next_.raw_literal_chars = &bookmark_next_raw_literal_;
 }
 
 
 void Scanner::Initialize(Utf16CharacterStream* source) {
   source_ = source;
   // Need to capture identifiers in order to recognize "get" and "set"
@@ skipping 504 matching lines @@
           }
         } else if (c0_ == '=') {
           token = Select(Token::ASSIGN_SUB);
         } else {
           token = Token::SUB;
         }
         break;
 
       case '*':
         // * *=
-        token = Select('=', Token::ASSIGN_MUL, Token::MUL);
+        Advance();
+        if (c0_ == '*' && allow_harmony_exponentiation_operator()) {
+          token = Select('=', Token::ASSIGN_EXP, Token::EXP);
+        } else if (c0_ == '=') {
+          token = Select(Token::ASSIGN_MUL);
+        } else {
+          token = Token::MUL;
+        }
         break;
 
       case '%':
         // % %=
         token = Select('=', Token::ASSIGN_MOD, Token::MOD);
         break;
 
       case '/':
         // /  // /* /=
         Advance();
@@ skipping 1091 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