Sloppy-mode let parsing

src/preparser.h

 // Copyright 2012 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.
 
 #ifndef V8_PREPARSER_H
 #define V8_PREPARSER_H
 
 #include "src/bailout-reason.h"
 #include "src/expression-classifier.h"
 #include "src/func-name-inferrer.h"
@@ skipping 320 matching lines @@
   bool stack_overflow() const { return stack_overflow_; }
   void set_stack_overflow() { stack_overflow_ = true; }
   Mode mode() const { return mode_; }
   Zone* zone() const { return zone_; }
 
   INLINE(Token::Value peek()) {
     if (stack_overflow_) return Token::ILLEGAL;
     return scanner()->peek();
   }
 
+  INLINE(Token::Value PeekAhead()) {
+    if (stack_overflow_) return Token::ILLEGAL;
+    return scanner()->PeekAhead();
+  }
+
   INLINE(Token::Value Next()) {
     if (stack_overflow_) return Token::ILLEGAL;
     {
       if (GetCurrentStackPosition() < stack_limit_) {
         // Any further calls to Next or peek will return the illegal token.
         // The current call must return the next token, which might already
         // have been peek'ed.
         stack_overflow_ = true;
       }
     }
@@ skipping 352 matching lines @@
                                              bool* ok);
 
   void ParseFormalParameter(FormalParametersT* parameters,
                             ExpressionClassifier* classifier, bool* ok);
   void ParseFormalParameterList(FormalParametersT* parameters,
                                 ExpressionClassifier* classifier, bool* ok);
   void CheckArityRestrictions(
       int param_count, FunctionLiteral::ArityRestriction arity_restriction,
       bool has_rest, int formals_start_pos, int formals_end_pos, bool* ok);
 
+  bool IsNextLetKeyword();
+
   // Checks if the expression is a valid reference expression (e.g., on the
   // left-hand side of assignments). Although ruled out by ECMA as early errors,
   // we allow calls for web compatibility and rewrite them to a runtime throw.
   ExpressionT CheckAndRewriteReferenceExpression(
       ExpressionT expression, int beg_pos, int end_pos,
       MessageTemplate::Template message, bool* ok);
   ExpressionT CheckAndRewriteReferenceExpression(
       ExpressionT expression, int beg_pos, int end_pos,
       MessageTemplate::Template message, ParseErrorType type, bool* ok);
 
@@ skipping 3016 matching lines @@
         *ok = false;
       }
       break;
     default:
       break;
   }
 }
 
 
 template <class Traits>
+bool ParserBase<Traits>::IsNextLetKeyword() {
+  DCHECK(peek() == Token::LET);
+  if (!allow_let()) {
+    return false;
+  }
+  Token::Value next_next = PeekAhead();
+  switch (next_next) {
+    case Token::LBRACE:
+    case Token::LBRACK:
+    case Token::IDENTIFIER:
+    case Token::STATIC:
+    case Token::LET:  // Yes, you can do let let = ... in sloppy mode
+    case Token::YIELD:
+      return true;
+    default:
+      return false;
+  }
+}
+
+
+template <class Traits>
 typename ParserBase<Traits>::ExpressionT
 ParserBase<Traits>::ParseArrowFunctionLiteral(
     const FormalParametersT& formal_parameters,
     const ExpressionClassifier& formals_classifier, bool* ok) {
   if (peek() == Token::ARROW && scanner_->HasAnyLineTerminatorBeforeNext()) {
     // ASI inserts `;` after arrow parameters if a line terminator is found.
     // `=> ...` is never a valid expression, so report as syntax error.
     // If next token is not `=>`, it's a syntax error anyways.
     ReportUnexpectedTokenAt(scanner_->peek_location(), Token::ARROW);
     *ok = false;
@@ skipping 287 matching lines @@
       *ok = false;
       return;
     }
     has_seen_constructor_ = true;
     return;
   }
 }
 } }  // v8::internal
 
 #endif  // V8_PREPARSER_H