[es6] Use strict arguments objects for destructured parameters

src/scopes.cc

 // 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.
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
 #include "src/bootstrapper.h"
 #include "src/messages.h"
 #include "src/parser.h"
@@ skipping 162 matching lines @@
   inner_scope_calls_eval_ = false;
   inner_scope_uses_arguments_ = false;
   force_eager_compilation_ = false;
   force_context_allocation_ = (outer_scope != NULL && !is_function_scope())
       ? outer_scope->has_forced_context_allocation() : false;
   num_var_or_const_ = 0;
   num_stack_slots_ = 0;
   num_heap_slots_ = 0;
   num_global_slots_ = 0;
   num_modules_ = 0;
-  module_var_ = NULL,
+  module_var_ = NULL;
+  has_simple_parameters_ = true;
   rest_parameter_ = NULL;
   rest_index_ = -1;
   scope_info_ = scope_info;
   start_position_ = RelocInfo::kNoPosition;
   end_position_ = RelocInfo::kNoPosition;
   if (!scope_info.is_null()) {
     scope_calls_eval_ = scope_info->CallsEval();
     language_mode_ = scope_info->language_mode();
     function_kind_ = scope_info->function_kind();
   }
@@ skipping 267 matching lines @@
 }
 
 
 Variable* Scope::DeclareParameter(const AstRawString* name, VariableMode mode,
                                   bool is_rest, bool* is_duplicate) {
   DCHECK(!already_resolved());
   DCHECK(is_function_scope());
   Variable* var;
   if (mode == TEMPORARY) {
     var = NewTemporary(name);
+    has_simple_parameters_ = false;
   } else {
     var = variables_.Declare(this, name, mode, Variable::NORMAL,
                              kCreatedInitialized);
     // TODO(wingo): Avoid O(n^2) check.
     *is_duplicate = IsDeclaredParameter(name);
   }
   if (is_rest) {
     DCHECK_NULL(rest_parameter_);
     rest_parameter_ = var;
     rest_index_ = num_parameters();
+    has_simple_parameters_ = false;
   }
   params_.Add(var, zone());
   return var;
 }
 
 
 Variable* Scope::DeclareLocal(const AstRawString* name, VariableMode mode,
                               InitializationFlag init_flag, Variable::Kind kind,
                               MaybeAssignedFlag maybe_assigned_flag,
                               int declaration_group_start) {
@@ skipping 901 matching lines @@
     // parameters, which is why we don't need to allocate an arguments
     // object in that case.
 
     // We are using 'arguments'. Tell the code generator that is needs to
     // allocate the arguments object by setting 'arguments_'.
     arguments_ = arguments;
 
     // In strict mode 'arguments' does not alias formal parameters.
     // Therefore in strict mode we allocate parameters as if 'arguments'
     // were not used.
-    uses_sloppy_arguments = is_sloppy(language_mode());
+    // If the parameter list is not simple, arguments isn't sloppy either.
+    uses_sloppy_arguments =
+        is_sloppy(language_mode()) && has_simple_parameters();
   }
 
   if (rest_parameter_ && !MustAllocate(rest_parameter_)) {
     rest_parameter_ = NULL;
   }
 
   // The same parameter may occur multiple times in the parameters_ list.
   // If it does, and if it is not copied into the context object, it must
   // receive the highest parameter index for that parameter; thus iteration
   // order is relevant!
@@ skipping 193 matching lines @@
       function_ != NULL && function_->proxy()->var()->IsContextSlot();
   return num_heap_slots() - Context::MIN_CONTEXT_SLOTS - num_global_slots() -
          (is_function_var_in_context ? 1 : 0);
 }
 
 
 int Scope::ContextGlobalCount() const { return num_global_slots(); }
 
 }  // namespace internal
 }  // namespace v8