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      1 //===- TemplateArgumentVisitor.h - Visitor for TArg subclasses --*- C++ -*-===//
      2 //
      3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
      4 // See https://llvm.org/LICENSE.txt for license information.
      5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
      6 //
      7 //===----------------------------------------------------------------------===//
      8 //
      9 //  This file defines the TemplateArgumentVisitor interface.
     10 //
     11 //===----------------------------------------------------------------------===//
     12 
     13 #ifndef LLVM_CLANG_AST_TEMPLATEARGUMENTVISITOR_H
     14 #define LLVM_CLANG_AST_TEMPLATEARGUMENTVISITOR_H
     15 
     16 #include "clang/AST/TemplateBase.h"
     17 
     18 namespace clang {
     19 
     20 namespace templateargumentvisitor {
     21 
     22 /// A simple visitor class that helps create template argument visitors.
     23 template <template <typename> class Ref, typename ImplClass,
     24           typename RetTy = void, typename... ParamTys>
     25 class Base {
     26 public:
     27 #define REF(CLASS) typename Ref<CLASS>::type
     28 #define DISPATCH(NAME)                                                         \
     29   case TemplateArgument::NAME:                                                 \
     30     return static_cast<ImplClass *>(this)->Visit##NAME##TemplateArgument(      \
     31         TA, std::forward<ParamTys>(P)...)
     32 
     33   RetTy Visit(REF(TemplateArgument) TA, ParamTys... P) {
     34     switch (TA.getKind()) {
     35       DISPATCH(Null);
     36       DISPATCH(Type);
     37       DISPATCH(Declaration);
     38       DISPATCH(NullPtr);
     39       DISPATCH(Integral);
     40       DISPATCH(Template);
     41       DISPATCH(TemplateExpansion);
     42       DISPATCH(Expression);
     43       DISPATCH(Pack);
     44     }
     45     llvm_unreachable("TemplateArgument is not covered in switch!");
     46   }
     47 
     48   // If the implementation chooses not to implement a certain visit
     49   // method, fall back to the parent.
     50 
     51 #define VISIT_METHOD(CATEGORY)                                                 \
     52   RetTy Visit##CATEGORY##TemplateArgument(REF(TemplateArgument) TA,            \
     53                                           ParamTys... P) {                     \
     54     return VisitTemplateArgument(TA, std::forward<ParamTys>(P)...);            \
     55   }
     56 
     57   VISIT_METHOD(Null);
     58   VISIT_METHOD(Type);
     59   VISIT_METHOD(Declaration);
     60   VISIT_METHOD(NullPtr);
     61   VISIT_METHOD(Integral);
     62   VISIT_METHOD(Template);
     63   VISIT_METHOD(TemplateExpansion);
     64   VISIT_METHOD(Expression);
     65   VISIT_METHOD(Pack);
     66 
     67   RetTy VisitTemplateArgument(REF(TemplateArgument), ParamTys...) {
     68     return RetTy();
     69   }
     70 
     71 #undef REF
     72 #undef DISPATCH
     73 #undef VISIT_METHOD
     74 };
     75 
     76 } // namespace templateargumentvisitor
     77 
     78 /// A simple visitor class that helps create template argument visitors.
     79 ///
     80 /// This class does not preserve constness of TemplateArgument references (see
     81 /// also ConstTemplateArgumentVisitor).
     82 template <typename ImplClass, typename RetTy = void, typename... ParamTys>
     83 class TemplateArgumentVisitor
     84     : public templateargumentvisitor::Base<std::add_lvalue_reference, ImplClass,
     85                                            RetTy, ParamTys...> {};
     86 
     87 /// A simple visitor class that helps create template argument visitors.
     88 ///
     89 /// This class preserves constness of TemplateArgument references (see also
     90 /// TemplateArgumentVisitor).
     91 template <typename ImplClass, typename RetTy = void, typename... ParamTys>
     92 class ConstTemplateArgumentVisitor
     93     : public templateargumentvisitor::Base<llvm::make_const_ref, ImplClass,
     94                                            RetTy, ParamTys...> {};
     95 
     96 } // namespace clang
     97 
     98 #endif // LLVM_CLANG_AST_TEMPLATEARGUMENTVISITOR_H
     99