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      1 //===- AttrVisitor.h - Visitor for Attr 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 AttrVisitor interface.
     10 //
     11 //===----------------------------------------------------------------------===//
     12 
     13 #ifndef LLVM_CLANG_AST_ATTRVISITOR_H
     14 #define LLVM_CLANG_AST_ATTRVISITOR_H
     15 
     16 #include "clang/AST/Attr.h"
     17 
     18 namespace clang {
     19 
     20 namespace attrvisitor {
     21 
     22 /// A simple visitor class that helps create attribute visitors.
     23 template <template <typename> class Ptr, typename ImplClass,
     24           typename RetTy = void, class... ParamTys>
     25 class Base {
     26 public:
     27 #define PTR(CLASS) typename Ptr<CLASS>::type
     28 #define DISPATCH(NAME)                                                         \
     29   return static_cast<ImplClass *>(this)->Visit##NAME(static_cast<PTR(NAME)>(A))
     30 
     31   RetTy Visit(PTR(Attr) A) {
     32     switch (A->getKind()) {
     33 
     34 #define ATTR(NAME)                                                             \
     35   case attr::NAME:                                                             \
     36     DISPATCH(NAME##Attr);
     37 #include "clang/Basic/AttrList.inc"
     38     }
     39     llvm_unreachable("Attr that isn't part of AttrList.inc!");
     40   }
     41 
     42   // If the implementation chooses not to implement a certain visit
     43   // method, fall back to the parent.
     44 #define ATTR(NAME)                                                             \
     45   RetTy Visit##NAME##Attr(PTR(NAME##Attr) A) { DISPATCH(Attr); }
     46 #include "clang/Basic/AttrList.inc"
     47 
     48   RetTy VisitAttr(PTR(Attr)) { return RetTy(); }
     49 
     50 #undef PTR
     51 #undef DISPATCH
     52 };
     53 
     54 } // namespace attrvisitor
     55 
     56 /// A simple visitor class that helps create attribute visitors.
     57 ///
     58 /// This class does not preserve constness of Attr pointers (see
     59 /// also ConstAttrVisitor).
     60 template <typename ImplClass, typename RetTy = void, typename... ParamTys>
     61 class AttrVisitor : public attrvisitor::Base<std::add_pointer, ImplClass, RetTy,
     62                                              ParamTys...> {};
     63 
     64 /// A simple visitor class that helps create attribute visitors.
     65 ///
     66 /// This class preserves constness of Attr pointers (see also
     67 /// AttrVisitor).
     68 template <typename ImplClass, typename RetTy = void, typename... ParamTys>
     69 class ConstAttrVisitor
     70     : public attrvisitor::Base<llvm::make_const_ptr, ImplClass, RetTy,
     71                                ParamTys...> {};
     72 
     73 } // namespace clang
     74 
     75 #endif // LLVM_CLANG_AST_ATTRVISITOR_H
     76