Parse harmony let declarations.

src/ast.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 357 matching lines @@
   Scope* block_scope_;
 };
 
 
 class Declaration: public AstNode {
  public:
   Declaration(VariableProxy* proxy, Variable::Mode mode, FunctionLiteral* fun)
       : proxy_(proxy),
         mode_(mode),
         fun_(fun) {
-    ASSERT(mode == Variable::VAR || mode == Variable::CONST);
+    ASSERT(mode == Variable::VAR ||
+           mode == Variable::CONST ||
+           mode == Variable::LET);
     // At the moment there are no "const functions"'s in JavaScript...
-    ASSERT(fun == NULL || mode == Variable::VAR);
+    ASSERT(fun == NULL || mode == Variable::VAR || mode == Variable::LET);
   }
 
   DECLARE_NODE_TYPE(Declaration)
 
   VariableProxy* proxy() const { return proxy_; }
   Variable::Mode mode() const { return mode_; }
   FunctionLiteral* fun() const { return fun_; }  // may be NULL
   virtual bool IsInlineable() const;
 
  private:
@@ skipping 1851 matching lines @@
 
  private:
   Isolate* isolate_;
   bool stack_overflow_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_AST_H_