Strict mode arguments do not share binding with formal parameters.

src/scopes.h

 // Copyright 2010 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 175 matching lines @@
 
   // ---------------------------------------------------------------------------
   // Scope-specific info.
 
   // Inform the scope that the corresponding code contains a with statement.
   void RecordWithStatement() { scope_contains_with_ = true; }
 
   // Inform the scope that the corresponding code contains an eval call.
   void RecordEvalCall() { scope_calls_eval_ = true; }
 
+  // Enable strict mode for the scope (unless disabled by a global flag).
+  void EnableStrictMode() {
+    strict_mode_ = FLAG_strict_mode;
+  }
 
   // ---------------------------------------------------------------------------
   // Predicates.
 
   // Specific scope types.
   bool is_eval_scope() const { return type_ == EVAL_SCOPE; }
   bool is_function_scope() const { return type_ == FUNCTION_SCOPE; }
   bool is_global_scope() const { return type_ == GLOBAL_SCOPE; }
+  bool is_strict_mode() const { return strict_mode_; }
 
   // Information about which scopes calls eval.
   bool calls_eval() const { return scope_calls_eval_; }
   bool outer_scope_calls_eval() const { return outer_scope_calls_eval_; }
 
   // Is this scope inside a with statement.
   bool inside_with() const { return scope_inside_with_; }
   // Does this scope contain a with statement.
   bool contains_with() const { return scope_contains_with_; }
 
@@ skipping 142 matching lines @@
   // Convenience variable; function scopes only.
   Variable* arguments_shadow_;
 
   // Illegal redeclaration.
   Expression* illegal_redecl_;
 
   // Scope-specific information.
   bool scope_inside_with_;  // this scope is inside a 'with' of some outer scope
   bool scope_contains_with_;  // this scope contains a 'with' statement
   bool scope_calls_eval_;  // this scope contains an 'eval' call
+  bool strict_mode_;  // this scope is a strict mode scope
 
   // Computed via PropagateScopeInfo.
   bool outer_scope_calls_eval_;
   bool inner_scope_calls_eval_;
   bool outer_scope_is_eval_scope_;
   bool force_eager_compilation_;
 
   // Computed via AllocateVariables; function scopes only.
   int num_stack_slots_;
   int num_heap_slots_;
@@ skipping 45 matching lines @@
     scope_name_ = Factory::empty_symbol();
     dynamics_ = NULL;
     receiver_ = NULL;
     function_ = NULL;
     arguments_ = NULL;
     arguments_shadow_ = NULL;
     illegal_redecl_ = NULL;
     scope_inside_with_ = false;
     scope_contains_with_ = false;
     scope_calls_eval_ = false;
+    // Inherit the strict mode from the parent scope.
+    strict_mode_ = (outer_scope != NULL) && outer_scope->strict_mode_;
     outer_scope_calls_eval_ = false;
     inner_scope_calls_eval_ = false;
     outer_scope_is_eval_scope_ = false;
     force_eager_compilation_ = false;
     num_stack_slots_ = 0;
     num_heap_slots_ = 0;
     scope_info_ = scope_info;
   }
 };
 
@@ skipping 44 matching lines @@
   int nesting_level_;
   // Nesting level of outermost scope that is contained in a with statement,
   // or kNotInsideWith if there are no with's around the current scope.
   int inside_with_level_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_SCOPES_H_