//===--- TypeVisitor.h - Visitor for Type subclasses ------------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines the TypeVisitor interface.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CLANG_AST_TYPEVISITOR_H
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#define LLVM_CLANG_AST_TYPEVISITOR_H
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#include "clang/AST/Type.h"
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namespace clang {
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#define DISPATCH(CLASS) \
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return static_cast<ImplClass*>(this)-> \
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Visit##CLASS(static_cast<const CLASS*>(T))
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/// \brief An operation on a type.
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///
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/// \tparam ImplClass Class implementing the operation. Must be inherited from
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/// TypeVisitor.
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/// \tparam RetTy %Type of result produced by the operation.
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///
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/// The class implements polymorphic operation on an object of type derived
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/// from Type. The operation is performed by calling method Visit. It then
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/// dispatches the call to function \c VisitFooType, if actual argument type
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/// is \c FooType.
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///
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/// The class implements static polymorphism using Curiously Recurring
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/// Template Pattern. It is designed to be a base class for some concrete
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/// class:
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///
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/// \code
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/// class SomeVisitor : public TypeVisitor<SomeVisitor,sometype> { ... };
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/// ...
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/// Type *atype = ...
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/// ...
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/// SomeVisitor avisitor;
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/// sometype result = avisitor.Visit(atype);
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/// \endcode
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///
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/// Actual treatment is made by methods of the derived class, TypeVisitor only
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/// dispatches call to the appropriate method. If the implementation class
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/// \c ImplClass provides specific action for some type, say
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/// \c ConstantArrayType, it should define method
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/// <tt>VisitConstantArrayType(const ConstantArrayType*)</tt>. Otherwise
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/// \c TypeVisitor dispatches call to the method that handles parent type. In
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/// this example handlers are tried in the sequence:
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///
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/// \li <tt>ImplClass::VisitConstantArrayType(const ConstantArrayType*)</tt>
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/// \li <tt>ImplClass::VisitArrayType(const ArrayType*)</tt>
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/// \li <tt>ImplClass::VisitType(const Type*)</tt>
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/// \li <tt>TypeVisitor::VisitType(const Type*)</tt>
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///
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/// The first function of this sequence that is defined will handle object of
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/// type \c ConstantArrayType.
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template<typename ImplClass, typename RetTy=void>
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class TypeVisitor {
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public:
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/// \brief Performs the operation associated with this visitor object.
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RetTy Visit(const Type *T) {
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// Top switch stmt: dispatch to VisitFooType for each FooType.
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switch (T->getTypeClass()) {
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#define ABSTRACT_TYPE(CLASS, PARENT)
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#define TYPE(CLASS, PARENT) case Type::CLASS: DISPATCH(CLASS##Type);
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#include "clang/AST/TypeNodes.def"
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}
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llvm_unreachable("Unknown type class!");
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}
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// If the implementation chooses not to implement a certain visit method, fall
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// back on superclass.
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#define TYPE(CLASS, PARENT) RetTy Visit##CLASS##Type(const CLASS##Type *T) { \
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DISPATCH(PARENT); \
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}
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#include "clang/AST/TypeNodes.def"
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/// \brief Method called if \c ImpClass doesn't provide specific handler
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/// for some type class.
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RetTy VisitType(const Type*) { return RetTy(); }
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};
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#undef DISPATCH
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} // end namespace clang
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#endif
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