[parser] Refactor AstTraversalVisitor

src/parsing/parser.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/parsing/parser.h"
 
 #include "src/api.h"
 #include "src/ast/ast.h"
 #include "src/ast/ast-expression-rewriter.h"
-#include "src/ast/ast-expression-visitor.h"
 #include "src/ast/ast-literal-reindexer.h"
+#include "src/ast/ast-traversal-visitor.h"
 #include "src/ast/scopeinfo.h"
 #include "src/bailout-reason.h"
 #include "src/base/platform/platform.h"
 #include "src/bootstrapper.h"
 #include "src/char-predicates-inl.h"
 #include "src/codegen.h"
 #include "src/compiler.h"
 #include "src/messages.h"
 #include "src/parsing/parameter-initializer-rewriter.h"
 #include "src/parsing/parser-base.h"
@@ skipping 4602 matching lines @@
       MessageTemplate::kNonCoercible, ast_value_factory()->empty_string(),
       kNoSourcePosition);
   IfStatement* if_statement = factory()->NewIfStatement(
       condition,
       factory()->NewExpressionStatement(throw_type_error, kNoSourcePosition),
       factory()->NewEmptyStatement(kNoSourcePosition), kNoSourcePosition);
   return if_statement;
 }
 
 
-class InitializerRewriter : public AstExpressionVisitor {
+class InitializerRewriter final
+    : public AstTraversalVisitor<InitializerRewriter> {
  public:
   InitializerRewriter(uintptr_t stack_limit, Expression* root, Parser* parser,
                       Scope* scope)
-      : AstExpressionVisitor(stack_limit, root),
+      : AstTraversalVisitor(stack_limit, root),
         parser_(parser),
         scope_(scope) {}
 
  private:
-  void VisitExpression(Expression* expr) override {
-    RewritableExpression* to_rewrite = expr->AsRewritableExpression();
-    if (to_rewrite == nullptr || to_rewrite->is_rewritten()) return;
+  // This is required so that the overriden Visit* methods can be
+  // called by the base class (template).
+  friend class AstTraversalVisitor<InitializerRewriter>;
 
+  // Just rewrite destructuring assignments wrapped in RewritableExpressions.
+  void VisitRewritableExpression(RewritableExpression* to_rewrite) {
+    if (to_rewrite->is_rewritten()) return;
     Parser::PatternRewriter::RewriteDestructuringAssignment(parser_, to_rewrite,
                                                             scope_);
   }
 
   // Code in function literals does not need to be eagerly rewritten, it will be
   // rewritten when scheduled.
-  void VisitFunctionLiteral(FunctionLiteral* expr) override {}
+  void VisitFunctionLiteral(FunctionLiteral* expr) {}
 
- private:
   Parser* parser_;
   Scope* scope_;
 };
 
 
 void Parser::RewriteParameterInitializer(Expression* expr, Scope* scope) {
   InitializerRewriter rewriter(stack_limit_, expr, this, scope);
   rewriter.Run();
 }
 
@@ skipping 2411 matching lines @@
   node->Print(Isolate::Current());
 }
 #endif  // DEBUG
 
 #undef CHECK_OK
 #undef CHECK_OK_VOID
 #undef CHECK_FAILED
 
 }  // namespace internal
 }  // namespace v8