1//===--- TypeVisitor.h - Visitor for Type subclasses ------------*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file defines the TypeVisitor interface. 11// 12//===----------------------------------------------------------------------===// 13 14#ifndef LLVM_CLANG_AST_TYPEVISITOR_H 15#define LLVM_CLANG_AST_TYPEVISITOR_H 16 17#include "clang/AST/Type.h" 18 19namespace clang { 20 21#define DISPATCH(CLASS) \ 22 return static_cast<ImplClass*>(this)-> \ 23 Visit##CLASS(static_cast<const CLASS*>(T)) 24 25/// \brief An operation on a type. 26/// 27/// \tparam ImplClass Class implementing the operation. Must be inherited from 28/// TypeVisitor. 29/// \tparam RetTy %Type of result produced by the operation. 30/// 31/// The class implements polymorphic operation on an object of type derived 32/// from Type. The operation is performed by calling method Visit. It then 33/// dispatches the call to function \c VisitFooType, if actual argument type 34/// is \c FooType. 35/// 36/// The class implements static polymorphism using Curiously Recurring 37/// Template Pattern. It is designed to be a base class for some concrete 38/// class: 39/// 40/// \code 41/// class SomeVisitor : public TypeVisitor<SomeVisitor,sometype> { ... }; 42/// ... 43/// Type *atype = ... 44/// ... 45/// SomeVisitor avisitor; 46/// sometype result = avisitor.Visit(atype); 47/// \endcode 48/// 49/// Actual treatment is made by methods of the derived class, TypeVisitor only 50/// dispatches call to the appropriate method. If the implementation class 51/// \c ImplClass provides specific action for some type, say 52/// \c ConstantArrayType, it should define method 53/// <tt>VisitConstantArrayType(const ConstantArrayType*)</tt>. Otherwise 54/// \c TypeVisitor dispatches call to the method that handles parent type. In 55/// this example handlers are tried in the sequence: 56/// 57/// \li <tt>ImplClass::VisitConstantArrayType(const ConstantArrayType*)</tt> 58/// \li <tt>ImplClass::VisitArrayType(const ArrayType*)</tt> 59/// \li <tt>ImplClass::VisitType(const Type*)</tt> 60/// \li <tt>TypeVisitor::VisitType(const Type*)</tt> 61/// 62/// The first function of this sequence that is defined will handle object of 63/// type \c ConstantArrayType. 64template<typename ImplClass, typename RetTy=void> 65class TypeVisitor { 66public: 67 68 /// \brief Performs the operation associated with this visitor object. 69 RetTy Visit(const Type *T) { 70 // Top switch stmt: dispatch to VisitFooType for each FooType. 71 switch (T->getTypeClass()) { 72#define ABSTRACT_TYPE(CLASS, PARENT) 73#define TYPE(CLASS, PARENT) case Type::CLASS: DISPATCH(CLASS##Type); 74#include "clang/AST/TypeNodes.def" 75 } 76 llvm_unreachable("Unknown type class!"); 77 } 78 79 // If the implementation chooses not to implement a certain visit method, fall 80 // back on superclass. 81#define TYPE(CLASS, PARENT) RetTy Visit##CLASS##Type(const CLASS##Type *T) { \ 82 DISPATCH(PARENT); \ 83} 84#include "clang/AST/TypeNodes.def" 85 86 /// \brief Method called if \c ImpClass doesn't provide specific handler 87 /// for some type class. 88 RetTy VisitType(const Type*) { return RetTy(); } 89}; 90 91#undef DISPATCH 92 93} // end namespace clang 94 95#endif 96