Templatize AstVisitor with its subclass

src/compiler/ast-graph-builder.h

 // Copyright 2014 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_COMPILER_AST_GRAPH_BUILDER_H_
 #define V8_COMPILER_AST_GRAPH_BUILDER_H_
 
 #include "src/ast/ast.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/liveness-analyzer.h"
@@ skipping 14 matching lines @@
 class LoopAssignmentAnalysis;
 class LoopBuilder;
 class Node;
 class TypeHintAnalysis;
 
 
 // The AstGraphBuilder produces a high-level IR graph, based on an
 // underlying AST. The produced graph can either be compiled into a
 // stand-alone function or be wired into another graph for the purposes
 // of function inlining.
-class AstGraphBuilder : public AstVisitor {
+// This AstVistor is not final, and provides the AstVisitor methods as virtual
+// methods so they can be specialized by subclasses.
+class AstGraphBuilder : public AstVisitor<AstGraphBuilder> {
  public:
   AstGraphBuilder(Zone* local_zone, CompilationInfo* info, JSGraph* jsgraph,
                   LoopAssignmentAnalysis* loop_assignment = nullptr,
                   TypeHintAnalysis* type_hint_analysis = nullptr);
+  virtual ~AstGraphBuilder() {}
 
   // Creates a graph by visiting the entire AST.
   bool CreateGraph(bool stack_check = true);
 
   // Helpers to create new control nodes.
   Node* NewIfTrue() { return NewNode(common()->IfTrue()); }
   Node* NewIfFalse() { return NewNode(common()->IfFalse()); }
   Node* NewMerge() { return NewNode(common()->Merge(1), true); }
   Node* NewLoop() { return NewNode(common()->Loop(1), true); }
   Node* NewBranch(Node* condition, BranchHint hint = BranchHint::kNone) {
     return NewNode(common()->Branch(hint), condition);
   }
 
  protected:
-#define DECLARE_VISIT(type) void Visit##type(type* node) override;
+#define DECLARE_VISIT(type) virtual void Visit##type(type* node);
   // Visiting functions for AST nodes make this an AstVisitor.
   AST_NODE_LIST(DECLARE_VISIT)
 #undef DECLARE_VISIT
 
   // Visiting function for declarations list is overridden.
-  void VisitDeclarations(ZoneList<Declaration*>* declarations) override;
+  void VisitDeclarations(ZoneList<Declaration*>* declarations);
 
  private:
   class AstContext;
   class AstEffectContext;
   class AstValueContext;
   class AstTestContext;
   class ContextScope;
   class ControlScope;
   class ControlScopeForBreakable;
   class ControlScopeForIteration;
@@ skipping 537 matching lines @@
 
   // Prepare environment to be used as loop header.
   void PrepareForLoop(BitVector* assigned, bool is_osr = false);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_AST_GRAPH_BUILDER_H_