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291 lines
8.8 KiB
C++
291 lines
8.8 KiB
C++
//===-- Support/Casting.h - Allow flexible, checked, casts -------*- C++ -*--=//
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//
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// This file defines the isa<X>(), cast<X>(), dyn_cast<X>(), cast_or_null<X>(),
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// and dyn_cast_or_null<X>() templates.
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//
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//===----------------------------------------------------------------------===//
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#ifndef SUPPORT_CASTING_H
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#define SUPPORT_CASTING_H
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#include <assert.h>
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//===----------------------------------------------------------------------===//
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// isa<x> Support Templates
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//===----------------------------------------------------------------------===//
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template<typename FromCl> struct isa_impl_cl;
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// Define a template that can be specialized by smart pointers to reflect the
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// fact that they are automatically dereferenced, and are not involved with the
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// template selection process... the default implementation is a noop.
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//
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template<typename From> struct simplify_type {
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typedef From SimpleType; // The real type this represents...
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// An accessor to get the real value...
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static SimpleType &getSimplifiedValue(From &Val) { return Val; }
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};
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template<typename From> struct simplify_type<const From> {
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typedef const From SimpleType;
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static SimpleType &getSimplifiedValue(const From &Val) {
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return simplify_type<From>::getSimplifiedValue((From&)Val);
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}
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};
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// isa<X> - Return true if the parameter to the template is an instance of the
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// template type argument. Used like this:
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//
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// if (isa<Type*>(myVal)) { ... }
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//
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template <typename To, typename From>
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inline bool isa_impl(const From &Val) {
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return To::classof(&Val);
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}
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template<typename To, typename From, typename SimpleType>
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struct isa_impl_wrap {
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// When From != SimplifiedType, we can simplify the type some more by using
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// the simplify_type template.
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static bool doit(const From &Val) {
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return isa_impl_cl<const SimpleType>::template
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isa<To>(simplify_type<const From>::getSimplifiedValue(Val));
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}
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};
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template<typename To, typename FromTy>
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struct isa_impl_wrap<To, const FromTy, const FromTy> {
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// When From == SimpleType, we are as simple as we are going to get.
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static bool doit(const FromTy &Val) {
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return isa_impl<To,FromTy>(Val);
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}
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};
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// isa_impl_cl - Use class partial specialization to transform types to a single
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// cannonical form for isa_impl.
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//
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template<typename FromCl>
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struct isa_impl_cl {
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template<class ToCl>
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static bool isa(const FromCl &Val) {
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return isa_impl_wrap<ToCl,const FromCl,
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simplify_type<const FromCl>::SimpleType>::doit(Val);
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}
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};
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// Specialization used to strip const qualifiers off of the FromCl type...
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template<typename FromCl>
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struct isa_impl_cl<const FromCl> {
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template<class ToCl>
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static bool isa(const FromCl &Val) {
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return isa_impl_cl<FromCl>::template isa<ToCl>(Val);
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}
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};
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// Define pointer traits in terms of base traits...
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template<class FromCl>
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struct isa_impl_cl<FromCl*> {
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template<class ToCl>
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static bool isa(FromCl *Val) {
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return isa_impl_cl<FromCl>::template isa<ToCl>(*Val);
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}
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};
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// Define reference traits in terms of base traits...
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template<class FromCl>
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struct isa_impl_cl<FromCl&> {
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template<class ToCl>
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static bool isa(FromCl &Val) {
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return isa_impl_cl<FromCl>::template isa<ToCl>(&Val);
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}
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};
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template <class X, class Y>
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inline bool isa(const Y &Val) {
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return isa_impl_cl<Y>::template isa<X>(Val);
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}
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//===----------------------------------------------------------------------===//
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// cast<x> Support Templates
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//===----------------------------------------------------------------------===//
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template<class To, class From> struct cast_retty;
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// Calculate what type the 'cast' function should return, based on a requested
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// type of To and a source type of From.
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template<class To, class From> struct cast_retty_impl {
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typedef To& ret_type; // Normal case, return Ty&
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};
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template<class To, class From> struct cast_retty_impl<To, const From> {
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typedef const To &ret_type; // Normal case, return Ty&
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};
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template<class To, class From> struct cast_retty_impl<To, From*> {
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typedef To* ret_type; // Pointer arg case, return Ty*
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};
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template<class To, class From> struct cast_retty_impl<To, const From*> {
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typedef const To* ret_type; // Constant pointer arg case, return const Ty*
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};
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template<class To, class From> struct cast_retty_impl<To, const From*const> {
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typedef const To* ret_type; // Constant pointer arg case, return const Ty*
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};
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template<class To, class From, class SimpleFrom>
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struct cast_retty_wrap {
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// When the simplified type and the from type are not the same, use the type
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// simplifier to reduce the type, then reuse cast_retty_impl to get the
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// resultant type.
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typedef typename cast_retty<To, SimpleFrom>::ret_type ret_type;
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};
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template<class To, class FromTy>
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struct cast_retty_wrap<To, FromTy, FromTy> {
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// When the simplified type is equal to the from type, use it directly.
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typedef typename cast_retty_impl<To,FromTy>::ret_type ret_type;
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};
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template<class To, class From>
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struct cast_retty {
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typedef typename cast_retty_wrap<To, From,
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simplify_type<From>::SimpleType>::ret_type ret_type;
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};
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// Ensure the non-simple values are converted using the simplify_type template
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// that may be specialized by smart pointers...
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//
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template<class To, class From, class SimpleFrom> struct cast_convert_val {
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// This is not a simple type, use the template to simplify it...
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static cast_retty<To, From>::ret_type doit(const From &Val) {
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return cast_convert_val<To, SimpleFrom,
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simplify_type<SimpleFrom>::SimpleType>::doit(
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simplify_type<From>::getSimplifiedValue(Val));
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}
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};
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template<class To, class FromTy> struct cast_convert_val<To,FromTy,FromTy> {
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// This _is_ a simple type, just cast it.
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static cast_retty<To, FromTy>::ret_type doit(const FromTy &Val) {
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return (cast_retty<To, FromTy>::ret_type)Val;
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}
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};
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// cast<X> - Return the argument parameter cast to the specified type. This
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// casting operator asserts that the type is correct, so it does not return null
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// on failure. But it will correctly return NULL when the input is NULL.
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// Used Like this:
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//
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// cast<Instruction>(myVal)->getParent()
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//
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template <class X, class Y>
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inline cast_retty<X, Y>::ret_type cast(const Y &Val) {
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assert(isa<X>(Val) && "cast<Ty>() argument of uncompatible type!");
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return cast_convert_val<X, Y, simplify_type<Y>::SimpleType>::doit(Val);
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}
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// cast_or_null<X> - Functionally identical to cast, except that a null value is
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// accepted.
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//
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template <class X, class Y>
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inline cast_retty<X, Y*>::ret_type cast_or_null(Y *Val) {
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if (Val == 0) return 0;
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assert(isa<X>(Val) && "cast_or_null<Ty>() argument of uncompatible type!");
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return cast<X>(Val);
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}
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// dyn_cast<X> - Return the argument parameter cast to the specified type. This
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// casting operator returns null if the argument is of the wrong type, so it can
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// be used to test for a type as well as cast if successful. This should be
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// used in the context of an if statement like this:
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//
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// if (const Instruction *I = dyn_cast<const Instruction>(myVal)) { ... }
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//
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template <class X, class Y>
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inline cast_retty<X, Y*>::ret_type dyn_cast(Y *Val) {
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return isa<X>(Val) ? cast<X, Y*>(Val) : 0;
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}
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// dyn_cast_or_null<X> - Functionally identical to dyn_cast, except that a null
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// value is accepted.
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//
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template <class X, class Y>
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inline cast_retty<X, Y*>::ret_type dyn_cast_or_null(Y *Val) {
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return (Val && isa<X>(Val)) ? cast<X, Y*>(Val) : 0;
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}
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#ifdef DEBUG_CAST_OPERATORS
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#include <iostream>
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struct bar {
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bar() {}
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private:
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bar(const bar &);
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};
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struct foo {
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void ext() const;
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/* static bool classof(const bar *X) {
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cerr << "Classof: " << X << "\n";
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return true;
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}*/
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};
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template <> inline bool isa_impl<foo,bar>(const bar &Val) {
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cerr << "Classof: " << &Val << "\n";
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return true;
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}
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bar *fub();
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void test(bar &B1, const bar *B2) {
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// test various configurations of const
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const bar &B3 = B1;
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const bar *const B4 = B2;
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// test isa
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if (!isa<foo>(B1)) return;
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if (!isa<foo>(B2)) return;
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if (!isa<foo>(B3)) return;
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if (!isa<foo>(B4)) return;
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// test cast
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foo &F1 = cast<foo>(B1);
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const foo *F3 = cast<foo>(B2);
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const foo *F4 = cast<foo>(B2);
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const foo &F8 = cast<foo>(B3);
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const foo *F9 = cast<foo>(B4);
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foo *F10 = cast<foo>(fub());
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// test cast_or_null
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const foo *F11 = cast_or_null<foo>(B2);
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const foo *F12 = cast_or_null<foo>(B2);
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const foo *F13 = cast_or_null<foo>(B4);
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const foo *F14 = cast_or_null<foo>(fub()); // Shouldn't print.
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// These lines are errors...
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//foo *F20 = cast<foo>(B2); // Yields const foo*
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//foo &F21 = cast<foo>(B3); // Yields const foo&
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//foo *F22 = cast<foo>(B4); // Yields const foo*
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//foo &F23 = cast_or_null<foo>(B1);
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//const foo &F24 = cast_or_null<foo>(B3);
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}
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bar *fub() { return 0; }
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void main() {
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bar B;
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test(B, &B);
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}
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#endif
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#endif
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