[strong] make function and class declarations lexical & immutable

src/ast.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_AST_H_
 #define V8_AST_H_
 
 #include "src/v8.h"
 
 #include "src/assembler.h"
@@ skipping 559 matching lines @@
 
  protected:
   FunctionDeclaration(Zone* zone,
                       VariableProxy* proxy,
                       VariableMode mode,
                       FunctionLiteral* fun,
                       Scope* scope,
                       int pos)
       : Declaration(zone, proxy, mode, scope, pos),
         fun_(fun) {
-    // At the moment there are no "const functions" in JavaScript...
-    DCHECK(mode == VAR || mode == LET);
+    DCHECK(mode == VAR || mode == LET || mode == CONST);
     DCHECK(fun != NULL);
   }
 
  private:
   FunctionLiteral* fun_;
 };
 
 
 class ModuleDeclaration FINAL : public Declaration {
  public:
@@ skipping 2899 matching lines @@
 
  private:
   Zone* zone_;
   AstValueFactory* ast_value_factory_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_AST_H_