Sloppy-mode let parsing

src/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 <stdint.h>
 
 #include <cmath>
 
@@ skipping 220 matching lines @@
   Token::ILLEGAL
 };
 
 
 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 (next_next_.token != Token::UNINITIALIZED) {
+    next_ = next_next_;
+    next_next_.token = Token::UNINITIALIZED;
+    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_;
+  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) {
   // The Unicode value U+FFFE is guaranteed never to be assigned as a
   // Unicode character; this implies that in a Unicode context the
   // 0xFF, 0xFE byte pattern can only be interpreted as the U+FEFF
   // character expressed in little-endian byte order (since it could
   // not be a U+FFFE character expressed in big-endian byte
   // order). Nevertheless, we check for it to be compatible with
   // Spidermonkey.
   return c == 0xFFFE;
@@ skipping 1346 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