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File indexing completed on 2026-05-10 08:36:46
0001 //===--- TypeVisitor.h - Visitor for Type subclasses ------------*- C++ -*-===// 0002 // 0003 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 0004 // See https://llvm.org/LICENSE.txt for license information. 0005 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 0006 // 0007 //===----------------------------------------------------------------------===// 0008 // 0009 // This file defines the TypeVisitor interface. 0010 // 0011 //===----------------------------------------------------------------------===// 0012 0013 #ifndef LLVM_CLANG_AST_TYPEVISITOR_H 0014 #define LLVM_CLANG_AST_TYPEVISITOR_H 0015 0016 #include "clang/AST/Type.h" 0017 0018 namespace clang { 0019 0020 #define DISPATCH(CLASS) \ 0021 return static_cast<ImplClass*>(this)-> \ 0022 Visit##CLASS(static_cast<const CLASS*>(T)) 0023 0024 /// An operation on a type. 0025 /// 0026 /// \tparam ImplClass Class implementing the operation. Must be inherited from 0027 /// TypeVisitor. 0028 /// \tparam RetTy %Type of result produced by the operation. 0029 /// 0030 /// The class implements polymorphic operation on an object of type derived 0031 /// from Type. The operation is performed by calling method Visit. It then 0032 /// dispatches the call to function \c VisitFooType, if actual argument type 0033 /// is \c FooType. 0034 /// 0035 /// The class implements static polymorphism using Curiously Recurring 0036 /// Template Pattern. It is designed to be a base class for some concrete 0037 /// class: 0038 /// 0039 /// \code 0040 /// class SomeVisitor : public TypeVisitor<SomeVisitor,sometype> { ... }; 0041 /// ... 0042 /// Type *atype = ... 0043 /// ... 0044 /// SomeVisitor avisitor; 0045 /// sometype result = avisitor.Visit(atype); 0046 /// \endcode 0047 /// 0048 /// Actual treatment is made by methods of the derived class, TypeVisitor only 0049 /// dispatches call to the appropriate method. If the implementation class 0050 /// \c ImplClass provides specific action for some type, say 0051 /// \c ConstantArrayType, it should define method 0052 /// <tt>VisitConstantArrayType(const ConstantArrayType*)</tt>. Otherwise 0053 /// \c TypeVisitor dispatches call to the method that handles parent type. In 0054 /// this example handlers are tried in the sequence: 0055 /// 0056 /// \li <tt>ImplClass::VisitConstantArrayType(const ConstantArrayType*)</tt> 0057 /// \li <tt>ImplClass::VisitArrayType(const ArrayType*)</tt> 0058 /// \li <tt>ImplClass::VisitType(const Type*)</tt> 0059 /// \li <tt>TypeVisitor::VisitType(const Type*)</tt> 0060 /// 0061 /// The first function of this sequence that is defined will handle object of 0062 /// type \c ConstantArrayType. 0063 template<typename ImplClass, typename RetTy=void> 0064 class TypeVisitor { 0065 public: 0066 0067 /// Performs the operation associated with this visitor object. 0068 RetTy Visit(const Type *T) { 0069 // Top switch stmt: dispatch to VisitFooType for each FooType. 0070 switch (T->getTypeClass()) { 0071 #define ABSTRACT_TYPE(CLASS, PARENT) 0072 #define TYPE(CLASS, PARENT) case Type::CLASS: DISPATCH(CLASS##Type); 0073 #include "clang/AST/TypeNodes.inc" 0074 } 0075 llvm_unreachable("Unknown type class!"); 0076 } 0077 0078 // If the implementation chooses not to implement a certain visit method, fall 0079 // back on superclass. 0080 #define TYPE(CLASS, PARENT) RetTy Visit##CLASS##Type(const CLASS##Type *T) { \ 0081 DISPATCH(PARENT); \ 0082 } 0083 #include "clang/AST/TypeNodes.inc" 0084 0085 /// Method called if \c ImpClass doesn't provide specific handler 0086 /// for some type class. 0087 RetTy VisitType(const Type*) { return RetTy(); } 0088 }; 0089 0090 #undef DISPATCH 0091 0092 } // end namespace clang 0093 0094 #endif
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