Templatize AstVisitor with its subclass

src/crankshaft/typing.h

 // Copyright 2013 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_CRANKSHAFT_TYPING_H_
 #define V8_CRANKSHAFT_TYPING_H_
 
 #include "src/allocation.h"
 #include "src/ast/ast-type-bounds.h"
 #include "src/ast/ast.h"
 #include "src/ast/scopes.h"
 #include "src/effects.h"
 #include "src/type-info.h"
 #include "src/types.h"
 #include "src/zone.h"
 
 namespace v8 {
 namespace internal {
 
-class AstTyper: public AstVisitor {
+class AstTyper final : public AstVisitor<AstTyper> {
  public:
   AstTyper(Isolate* isolate, Zone* zone, Handle<JSFunction> closure,
            Scope* scope, BailoutId osr_ast_id, FunctionLiteral* root,
            AstTypeBounds* bounds);
   void Run();
 
   DEFINE_AST_VISITOR_SUBCLASS_MEMBERS();
 
  private:
   Effect ObservedOnStack(Object* value);
@@ skipping 33 matching lines @@
   int stack_local_index(int index) { return index; }
 
   int variable_index(Variable* var) {
     // Stack locals have the range [0 .. l]
     // Parameters have the range [-1 .. p]
     // We map this to [-p-2 .. -1, 0 .. l]
     return var->IsStackLocal() ? stack_local_index(var->index()) :
            var->IsParameter() ? parameter_index(var->index()) : kNoVar;
   }
 
-  void VisitDeclarations(ZoneList<Declaration*>* declarations) override;
-  void VisitStatements(ZoneList<Statement*>* statements) override;
+  void VisitDeclarations(ZoneList<Declaration*>* declarations);
+  void VisitStatements(ZoneList<Statement*>* statements);
 
-#define DECLARE_VISIT(type) void Visit##type(type* node) override;
+#define DECLARE_VISIT(type) void Visit##type(type* node);
   AST_NODE_LIST(DECLARE_VISIT)
 #undef DECLARE_VISIT
 
   DISALLOW_COPY_AND_ASSIGN(AstTyper);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_CRANKSHAFT_TYPING_H_