[es6] Implement inner scope for functions with destructuring

src/scopes.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_SCOPES_H_
 #define V8_SCOPES_H_
 
 #include "src/ast.h"
 #include "src/pending-compilation-error-handler.h"
 #include "src/zone.h"
@@ skipping 262 matching lines @@
   bool is_eval_scope() const { return scope_type_ == EVAL_SCOPE; }
   bool is_function_scope() const {
     return scope_type_ == FUNCTION_SCOPE || scope_type_ == ARROW_SCOPE;
   }
   bool is_module_scope() const { return scope_type_ == MODULE_SCOPE; }
   bool is_script_scope() const { return scope_type_ == SCRIPT_SCOPE; }
   bool is_catch_scope() const { return scope_type_ == CATCH_SCOPE; }
   bool is_block_scope() const { return scope_type_ == BLOCK_SCOPE; }
   bool is_with_scope() const { return scope_type_ == WITH_SCOPE; }
   bool is_arrow_scope() const { return scope_type_ == ARROW_SCOPE; }
-  bool is_declaration_scope() const {
-    return is_eval_scope() || is_function_scope() ||
-        is_module_scope() || is_script_scope();
-  }
+  bool is_declaration_scope() const { return is_declaration_scope_; }
   bool is_strict_eval_scope() const {
     return is_eval_scope() && is_strict(language_mode_);
   }
 
+  void set_is_declaration_scope() { is_declaration_scope_ = true; }
+
   // Information about which scopes calls eval.
   bool calls_eval() const { return scope_calls_eval_; }
   bool calls_sloppy_eval() {
     return scope_calls_eval_ && is_sloppy(language_mode_);
   }
   bool outer_scope_calls_sloppy_eval() const {
     return outer_scope_calls_sloppy_eval_;
   }
   bool asm_module() const { return asm_module_; }
   bool asm_function() const { return asm_function_; }
@@ skipping 306 matching lines @@
   bool outer_scope_calls_sloppy_eval_;
   bool inner_scope_calls_eval_;
   bool inner_scope_uses_arguments_;
   bool force_eager_compilation_;
   bool force_context_allocation_;
 
   // True if it doesn't need scope resolution (e.g., if the scope was
   // constructed based on a serialized scope info or a catch context).
   bool already_resolved_;
 
+  // True if it holds 'var' declarations.
+  bool is_declaration_scope_;
+
   // Computed as variables are declared.
   int num_var_or_const_;
 
   // Computed via AllocateVariables; function, block and catch scopes only.
   int num_stack_slots_;
   int num_heap_slots_;
   int num_global_slots_;
 
   // The number of modules (including nested ones).
   int num_modules_;
@@ skipping 134 matching lines @@
   PendingCompilationErrorHandler pending_error_handler_;
 
   // For tracking which classes are declared consecutively. Needed for strong
   // mode.
   int class_declaration_group_start_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_SCOPES_H_