[parser] disallow language mode directive in body of function with non-simple parameters

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 369 matching lines @@
     *index = rest_index_;
     if (rest_index_ < 0) return NULL;
     return rest_parameter_;
   }
 
   bool has_rest_parameter() const {
     return rest_index_ >= 0;
   }
 
   bool has_simple_parameters() const {
+    return has_simple_parameters_;
+  }
+
+  // TODO(caitp): manage this state in a better way. PreParser must be able to
+  // communicate that the scope is non-simple, without allocating any parameters
+  // as the Parser does. This is necessary to ensure that TC39's proposed early
+  // error can be reported consistently regardless of whether lazily parsed or
+  // not.
+  void SetHasNonSimpleParameters() {
     DCHECK(is_function_scope());
-    return has_simple_parameters_;
+    has_simple_parameters_ = false;
+  }
+
+  // Retrieve `IsSimpleParameterList` of current or outer function.
+  bool HasSimpleParameters() {
+    Scope* scope = ClosureScope();
+    return !scope->is_function_scope() || scope->has_simple_parameters();
   }
 
   // The local variable 'arguments' if we need to allocate it; NULL otherwise.
   Variable* arguments() const {
     DCHECK(!is_arrow_scope() || arguments_ == nullptr);
     return arguments_;
   }
 
   Variable* this_function_var() const {
     // This is only used in derived constructors atm.
@@ skipping 361 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_