[parser] Enforce module-specific identifier restriction

src/ast/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_AST_SCOPES_H_
 #define V8_AST_SCOPES_H_
 
 #include "src/ast/ast.h"
 #include "src/hashmap.h"
 #include "src/pending-compilation-error-handler.h"
@@ skipping 225 matching lines @@
   void RecordEvalCall() { scope_calls_eval_ = true; }
 
   // Inform the scope that the corresponding code uses "arguments".
   void RecordArgumentsUsage() { scope_uses_arguments_ = true; }
 
   // Inform the scope that the corresponding code uses "super".
   void RecordSuperPropertyUsage() { scope_uses_super_property_ = true; }
 
   // Set the language mode flag (unless disabled by a global flag).
   void SetLanguageMode(LanguageMode language_mode) {
-    DCHECK(!is_module_scope());
+    DCHECK(!is_module_scope() || is_strict(language_mode));
     language_mode_ = language_mode;
   }
 
   // Set the ASM module flag.
   void SetAsmModule() { asm_module_ = true; }
 
   // Inform the scope that the scope may execute declarations nonlinearly.
   // Currently, the only nonlinear scope is a switch statement. The name is
   // more general in case something else comes up with similar control flow,
   // for example the ability to break out of something which does not have
@@ skipping 553 matching lines @@
   AstValueFactory* ast_value_factory_;
   Zone* zone_;
 
   PendingCompilationErrorHandler pending_error_handler_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_AST_SCOPES_H_