2 // Copyright 2000 John Maddock (john@johnmaddock.co.uk)
3 // Copyright 2000 Jeremy Siek (jsiek@lsc.nd.edu)
4 // Copyright 1999, 2000 Jaakko Jarvi (jaakko.jarvi@cs.utu.fi)
6 // Use, modification and distribution are subject to the Boost Software License,
7 // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
8 // http://www.boost.org/LICENSE_1_0.txt).
10 // See http://www.boost.org/libs/type_traits for most recent version including documentation.
12 #ifndef BOOST_TT_IS_CONVERTIBLE_HPP_INCLUDED
13 #define BOOST_TT_IS_CONVERTIBLE_HPP_INCLUDED
15 #include <boost/type_traits/intrinsics.hpp>
16 #ifndef BOOST_IS_CONVERTIBLE
17 #include <boost/type_traits/detail/yes_no_type.hpp>
18 #include <boost/type_traits/config.hpp>
19 #include <boost/type_traits/is_array.hpp>
20 #include <boost/type_traits/add_reference.hpp>
21 #include <boost/type_traits/ice.hpp>
22 #include <boost/type_traits/is_arithmetic.hpp>
23 #include <boost/type_traits/is_void.hpp>
24 #ifndef BOOST_NO_IS_ABSTRACT
25 #include <boost/type_traits/is_abstract.hpp>
27 #include <boost/type_traits/add_rvalue_reference.hpp>
29 #if defined(__MWERKS__)
30 #include <boost/type_traits/is_function.hpp>
31 #include <boost/type_traits/remove_reference.hpp>
34 #endif // BOOST_IS_CONVERTIBLE
36 // should be always the last #include directive
37 #include <boost/type_traits/detail/bool_trait_def.hpp>
41 #ifndef BOOST_IS_CONVERTIBLE
43 // is one type convertable to another?
45 // there are multiple versions of the is_convertible
46 // template, almost every compiler seems to require its
49 // Thanks to Andrei Alexandrescu for the original version of the
50 // conversion detection technique!
55 // MS specific version:
57 #if defined(BOOST_MSVC) && (BOOST_MSVC <= 1300)
59 // This workaround is necessary to handle when From is void
60 // which is normally taken care of by the partial specialization
61 // of the is_convertible typename.
62 using ::boost::type_traits::yes_type;
63 using ::boost::type_traits::no_type;
65 template< typename From >
66 struct does_conversion_exist
68 template< typename To > struct result_
70 static no_type BOOST_TT_DECL _m_check(...);
71 static yes_type BOOST_TT_DECL _m_check(To);
72 static typename add_rvalue_reference<From>::type _m_from;
73 enum { value = sizeof( _m_check(_m_from) ) == sizeof(yes_type) };
78 struct does_conversion_exist<void>
80 template< typename To > struct result_
82 enum { value = ::boost::is_void<To>::value };
86 template <typename From, typename To>
87 struct is_convertible_basic_impl
88 : public does_conversion_exist<From>::template result_<To>
92 #elif defined(__BORLANDC__) && (__BORLANDC__ < 0x560)
94 // special version for Borland compilers
95 // this version breaks when used for some
98 template <typename From, typename To>
99 struct is_convertible_impl
101 #pragma option push -w-8074
102 // This workaround for Borland breaks the EDG C++ frontend,
103 // so we only use it for Borland.
104 template <typename T> struct checker
106 static ::boost::type_traits::no_type BOOST_TT_DECL _m_check(...);
107 static ::boost::type_traits::yes_type BOOST_TT_DECL _m_check(T);
110 static typename add_rvalue_reference<From>::type _m_from;
111 static bool const value = sizeof( checker<To>::_m_check(_m_from) )
112 == sizeof(::boost::type_traits::yes_type);
116 #elif defined(__GNUC__) || defined(__BORLANDC__) && (__BORLANDC__ < 0x600)
117 // special version for gcc compiler + recent Borland versions
118 // note that this does not pass UDT's through (...)
120 struct any_conversion
122 template <typename T> any_conversion(const volatile T&);
123 template <typename T> any_conversion(T&);
126 template <typename T> struct checker
128 static boost::type_traits::no_type _m_check(any_conversion ...);
129 static boost::type_traits::yes_type _m_check(T, int);
132 template <typename From, typename To>
133 struct is_convertible_basic_impl
135 static typename add_rvalue_reference<From>::type _m_from;
136 static bool const value = sizeof( boost::detail::checker<To>::_m_check(_m_from, 0) )
137 == sizeof(::boost::type_traits::yes_type);
140 #elif (defined(__EDG_VERSION__) && (__EDG_VERSION__ >= 245) && !defined(__ICL)) \
141 || defined(__IBMCPP__) || defined(__HP_aCC)
143 // This is *almost* an ideal world implementation as it doesn't rely
144 // on undefined behaviour by passing UDT's through (...).
145 // Unfortunately it doesn't quite pass all the tests for most compilers (sigh...)
146 // Enable this for your compiler if is_convertible_test.cpp will compile it...
148 // Note we do not enable this for VC7.1, because even though it passes all the
149 // type_traits tests it is known to cause problems when instantiation occurs
150 // deep within the instantiation tree :-(
152 struct any_conversion
154 template <typename T> any_conversion(const volatile T&);
155 // we need this constructor to catch references to functions
156 // (which can not be cv-qualified):
157 template <typename T> any_conversion(T&);
160 template <typename From, typename To>
161 struct is_convertible_basic_impl
163 static ::boost::type_traits::no_type BOOST_TT_DECL _m_check(any_conversion ...);
164 static ::boost::type_traits::yes_type BOOST_TT_DECL _m_check(To, int);
165 static typename add_rvalue_reference<From>::type _m_from;
167 BOOST_STATIC_CONSTANT(bool, value =
168 sizeof( _m_check(_m_from, 0) ) == sizeof(::boost::type_traits::yes_type)
172 #elif defined(__DMC__)
174 struct any_conversion
176 template <typename T> any_conversion(const volatile T&);
177 // we need this constructor to catch references to functions
178 // (which can not be cv-qualified):
179 template <typename T> any_conversion(T&);
182 template <typename From, typename To>
183 struct is_convertible_basic_impl
185 // Using '...' doesn't always work on Digital Mars. This version seems to.
187 static ::boost::type_traits::no_type BOOST_TT_DECL _m_check(any_conversion, float, T);
188 static ::boost::type_traits::yes_type BOOST_TT_DECL _m_check(To, int, int);
189 static typename add_rvalue_reference<From>::type _m_from;
191 // Static constants sometime cause the conversion of _m_from to To to be
192 // called. This doesn't happen with an enum.
194 sizeof( _m_check(_m_from, 0, 0) ) == sizeof(::boost::type_traits::yes_type)
198 #elif defined(__MWERKS__)
200 // CW works with the technique implemented above for EDG, except when From
201 // is a function type (or a reference to such a type), in which case
202 // any_conversion won't be accepted as a valid conversion. We detect this
203 // exceptional situation and channel it through an alternative algorithm.
206 template <typename From, typename To,bool FromIsFunctionRef>
207 struct is_convertible_basic_impl_aux;
209 struct any_conversion
211 template <typename T> any_conversion(const volatile T&);
214 template <typename From, typename To>
215 struct is_convertible_basic_impl_aux<From,To,false /*FromIsFunctionRef*/>
217 static ::boost::type_traits::no_type BOOST_TT_DECL _m_check(any_conversion ...);
218 static ::boost::type_traits::yes_type BOOST_TT_DECL _m_check(To, int);
219 static typename add_rvalue_reference<From>::type _m_from;
221 BOOST_STATIC_CONSTANT(bool, value =
222 sizeof( _m_check(_m_from, 0) ) == sizeof(::boost::type_traits::yes_type)
226 template <typename From, typename To>
227 struct is_convertible_basic_impl_aux<From,To,true /*FromIsFunctionRef*/>
229 static ::boost::type_traits::no_type BOOST_TT_DECL _m_check(...);
230 static ::boost::type_traits::yes_type BOOST_TT_DECL _m_check(To);
231 static typename add_rvalue_reference<From>::type _m_from;
232 BOOST_STATIC_CONSTANT(bool, value =
233 sizeof( _m_check(_m_from) ) == sizeof(::boost::type_traits::yes_type)
237 template <typename From, typename To>
238 struct is_convertible_basic_impl:
239 is_convertible_basic_impl_aux<
241 ::boost::is_function<typename ::boost::remove_reference<From>::type>::value
248 // This version seems to work pretty well for a wide spectrum of compilers,
249 // however it does rely on undefined behaviour by passing UDT's through (...).
251 template <typename From, typename To>
252 struct is_convertible_basic_impl
254 static ::boost::type_traits::no_type BOOST_TT_DECL _m_check(...);
255 static ::boost::type_traits::yes_type BOOST_TT_DECL _m_check(To);
256 static typename add_rvalue_reference<From>::type _m_from;
258 #pragma warning(push)
259 #pragma warning(disable:4244)
260 #if BOOST_WORKAROUND(BOOST_MSVC_FULL_VER, >= 140050000)
261 #pragma warning(disable:6334)
264 BOOST_STATIC_CONSTANT(bool, value =
265 sizeof( _m_check(_m_from) ) == sizeof(::boost::type_traits::yes_type)
272 #endif // is_convertible_impl
275 // As before, a static constant sometimes causes errors on Digital Mars.
276 template <typename From, typename To>
277 struct is_convertible_impl
279 typedef typename add_reference<From>::type ref_type;
281 (::boost::type_traits::ice_and<
282 ::boost::type_traits::ice_or<
283 ::boost::detail::is_convertible_basic_impl<ref_type,To>::value,
284 ::boost::is_void<To>::value
286 ::boost::type_traits::ice_not<
287 ::boost::is_array<To>::value
291 #elif !defined(__BORLANDC__) || __BORLANDC__ > 0x551
292 template <typename From, typename To>
293 struct is_convertible_impl
295 typedef typename add_reference<From>::type ref_type;
296 BOOST_STATIC_CONSTANT(bool, value =
297 (::boost::type_traits::ice_and<
298 ::boost::type_traits::ice_or<
299 ::boost::detail::is_convertible_basic_impl<ref_type,To>::value,
300 ::boost::is_void<To>::value
302 ::boost::type_traits::ice_not<
303 ::boost::is_array<To>::value
310 template <bool trivial1, bool trivial2, bool abstract_target>
311 struct is_convertible_impl_select
313 template <class From, class To>
316 typedef is_convertible_impl<From, To> type;
321 struct is_convertible_impl_select<true, true, false>
323 template <class From, class To>
326 typedef true_type type;
331 struct is_convertible_impl_select<false, false, true>
333 template <class From, class To>
336 typedef false_type type;
341 struct is_convertible_impl_select<true, false, true>
343 template <class From, class To>
346 typedef false_type type;
350 template <typename From, typename To>
351 struct is_convertible_impl_dispatch_base
353 #if !BOOST_WORKAROUND(__HP_aCC, < 60700)
354 typedef is_convertible_impl_select<
355 ::boost::is_arithmetic<From>::value,
356 ::boost::is_arithmetic<To>::value,
357 #ifndef BOOST_NO_IS_ABSTRACT
358 ::boost::is_abstract<To>::value
364 typedef is_convertible_impl_select<false, false, false> selector;
366 typedef typename selector::template rebind<From, To> isc_binder;
367 typedef typename isc_binder::type type;
370 template <typename From, typename To>
371 struct is_convertible_impl_dispatch
372 : public is_convertible_impl_dispatch_base<From, To>::type
376 // Now add the full and partial specialisations
377 // for void types, these are common to all the
378 // implementation above:
380 #ifndef BOOST_NO_CV_VOID_SPECIALIZATIONS
381 # define TT_AUX_BOOL_CV_VOID_TRAIT_SPEC2_PART1(trait,spec1,spec2,value) \
382 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC2(trait,spec1,spec2,value) \
383 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC2(trait,spec1,spec2 const,value) \
384 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC2(trait,spec1,spec2 volatile,value) \
385 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC2(trait,spec1,spec2 const volatile,value) \
388 # define TT_AUX_BOOL_CV_VOID_TRAIT_SPEC2(trait,spec1,spec2,value) \
389 TT_AUX_BOOL_CV_VOID_TRAIT_SPEC2_PART1(trait,spec1,spec2,value) \
390 TT_AUX_BOOL_CV_VOID_TRAIT_SPEC2_PART1(trait,spec1 const,spec2,value) \
391 TT_AUX_BOOL_CV_VOID_TRAIT_SPEC2_PART1(trait,spec1 volatile,spec2,value) \
392 TT_AUX_BOOL_CV_VOID_TRAIT_SPEC2_PART1(trait,spec1 const volatile,spec2,value) \
395 TT_AUX_BOOL_CV_VOID_TRAIT_SPEC2(is_convertible,void,void,true)
397 # undef TT_AUX_BOOL_CV_VOID_TRAIT_SPEC2
398 # undef TT_AUX_BOOL_CV_VOID_TRAIT_SPEC2_PART1
401 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC2(is_convertible,void,void,true)
402 #endif // BOOST_NO_CV_VOID_SPECIALIZATIONS
404 #ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
405 BOOST_TT_AUX_BOOL_TRAIT_IMPL_PARTIAL_SPEC2_1(typename To,is_convertible,void,To,false)
406 BOOST_TT_AUX_BOOL_TRAIT_IMPL_PARTIAL_SPEC2_1(typename From,is_convertible,From,void,false)
407 #ifndef BOOST_NO_CV_VOID_SPECIALIZATIONS
408 BOOST_TT_AUX_BOOL_TRAIT_IMPL_PARTIAL_SPEC2_1(typename To,is_convertible,void const,To,false)
409 BOOST_TT_AUX_BOOL_TRAIT_IMPL_PARTIAL_SPEC2_1(typename To,is_convertible,void volatile,To,false)
410 BOOST_TT_AUX_BOOL_TRAIT_IMPL_PARTIAL_SPEC2_1(typename To,is_convertible,void const volatile,To,false)
411 BOOST_TT_AUX_BOOL_TRAIT_IMPL_PARTIAL_SPEC2_1(typename From,is_convertible,From,void const,false)
412 BOOST_TT_AUX_BOOL_TRAIT_IMPL_PARTIAL_SPEC2_1(typename From,is_convertible,From,void volatile,false)
413 BOOST_TT_AUX_BOOL_TRAIT_IMPL_PARTIAL_SPEC2_1(typename From,is_convertible,From,void const volatile,false)
415 #endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
417 } // namespace detail
419 BOOST_TT_AUX_BOOL_TRAIT_DEF2(is_convertible,From,To,(::boost::detail::is_convertible_impl_dispatch<From,To>::value))
423 BOOST_TT_AUX_BOOL_TRAIT_DEF2(is_convertible,From,To,BOOST_IS_CONVERTIBLE(From,To))
429 #include <boost/type_traits/detail/bool_trait_undef.hpp>
431 #endif // BOOST_TT_IS_CONVERTIBLE_HPP_INCLUDED