Introduce NewScriptScope that creates a top-level scope

src/parsing/parser-base.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_PARSING_PARSER_BASE_H
 #define V8_PARSING_PARSER_BASE_H
 
 #include "src/ast/scopes.h"
 #include "src/bailout-reason.h"
 #include "src/base/hashmap.h"
@@ skipping 597 matching lines @@
     }
     ~ParsingModeScope() {
       parser_->mode_ = old_mode_;
     }
 
    private:
     ParserBase* parser_;
     Mode old_mode_;
   };
 
+  Scope* NewScriptScope() {
+    return new (zone()) Scope(zone(), nullptr, SCRIPT_SCOPE, kNormalFunction);
+  }
+
   Scope* NewScope(Scope* parent, ScopeType scope_type) {
-    // Must always pass the function kind for FUNCTION_SCOPE.
-    DCHECK(scope_type != FUNCTION_SCOPE);
+    // Must always use the specific constructors for the blacklisted scope
+    // types.
+    DCHECK_NE(FUNCTION_SCOPE, scope_type);
+    DCHECK_NE(SCRIPT_SCOPE, scope_type);
+    DCHECK_NOT_NULL(parent);
     Scope* result =
         new (zone()) Scope(zone(), parent, scope_type, kNormalFunction);
     if (scope_type == MODULE_SCOPE) result->DeclareThis(ast_value_factory());
     return result;
   }
 
   Scope* NewFunctionScope(FunctionKind kind) {
     DCHECK(ast_value_factory());
     Scope* result = new (zone()) Scope(zone(), scope(), FUNCTION_SCOPE, kind);
     if (!IsArrowFunction(kind)) {
@@ skipping 3051 matching lines @@
     has_seen_constructor_ = true;
     return;
   }
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PARSING_PARSER_BASE_H