for-of should throw if result object is not an object

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 924 matching lines @@
     assign_iterator_ = assign_iterator;
     next_result_ = next_result;
     result_done_ = result_done;
     assign_each_ = assign_each;
   }
 
   Expression* iterable() const {
     return subject();
   }
 
-  // var iterator = subject[Symbol.iterator]();
+  // iterator = subject[Symbol.iterator]();
   Expression* assign_iterator() const {
     return assign_iterator_;
   }
 
-  // var result = iterator.next();
+  // result = iterator.next(); (with type check)
   Expression* next_result() const {
     return next_result_;
   }
 
   // result.done
   Expression* result_done() const {
     return result_done_;
   }
 
   // each = result.value
@@ skipping 2529 matching lines @@
 
  private:
   Zone* zone_;
   AstValueFactory* ast_value_factory_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_AST_H_