boost/type_traits/detail/has_binary_operator.hpp
// (C) Copyright 2009-2011 Frederic Bron, Robert Stewart, Steven Watanabe & Roman Perepelitsa.
//
// Use, modification and distribution are subject to the Boost Software License,
// Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt).
//
// See http://www.boost.org/libs/type_traits for most recent version including documentation.
#include <boost/config.hpp>
#include <boost/type_traits/detail/config.hpp>
// cannot include this header without getting warnings of the kind:
// gcc:
// warning: value computed is not used
// warning: comparison between signed and unsigned integer expressions
// msvc:
// warning C4018: '<' : signed/unsigned mismatch
// warning C4244: '+=' : conversion from 'double' to 'char', possible loss of data
// warning C4547: '*' : operator before comma has no effect; expected operator with side-effect
// warning C4800: 'int' : forcing value to bool 'true' or 'false' (performance warning)
// warning C4804: '<' : unsafe use of type 'bool' in operation
// warning C4805: '==' : unsafe mix of type 'bool' and type 'char' in operation
// cannot find another implementation -> declared as system header to suppress these warnings.
#if defined(__GNUC__)
# pragma GCC system_header
#elif defined(BOOST_MSVC)
# pragma warning ( push )
# pragma warning ( disable : 4018 4244 4547 4800 4804 4805 4913 4133)
# if BOOST_WORKAROUND(BOOST_MSVC_FULL_VER, >= 140050000)
# pragma warning ( disable : 6334)
# endif
#endif
#if defined(BOOST_TT_HAS_ACCURATE_BINARY_OPERATOR_DETECTION)
#include <boost/type_traits/integral_constant.hpp>
#include <boost/type_traits/make_void.hpp>
#include <boost/type_traits/is_convertible.hpp>
#include <boost/type_traits/is_void.hpp>
#include <boost/type_traits/add_reference.hpp>
#include <utility>
namespace boost
{
namespace binary_op_detail {
struct dont_care;
template <class T, class U, class Ret, class = void>
struct BOOST_JOIN(BOOST_TT_TRAIT_NAME, _ret_imp) : public boost::false_type {};
template <class T, class U, class Ret>
struct BOOST_JOIN(BOOST_TT_TRAIT_NAME, _ret_imp)<T, U, Ret, typename boost::make_void<decltype(std::declval<typename add_reference<T>::type>() BOOST_TT_TRAIT_OP std::declval<typename add_reference<U>::type>())>::type>
: public boost::integral_constant<bool, ::boost::is_convertible<decltype(std::declval<typename add_reference<T>::type>() BOOST_TT_TRAIT_OP std::declval<typename add_reference<U>::type>()), Ret>::value> {};
template <class T, class U, class = void >
struct BOOST_JOIN(BOOST_TT_TRAIT_NAME, _void_imp) : public boost::false_type {};
template <class T, class U>
struct BOOST_JOIN(BOOST_TT_TRAIT_NAME, _void_imp)<T, U, typename boost::make_void<decltype(std::declval<typename add_reference<T>::type>() BOOST_TT_TRAIT_OP std::declval<typename add_reference<U>::type>())>::type>
: public boost::integral_constant<bool, ::boost::is_void<decltype(std::declval<typename add_reference<T>::type>() BOOST_TT_TRAIT_OP std::declval<typename add_reference<U>::type>())>::value> {};
template <class T, class U, class = void>
struct BOOST_JOIN(BOOST_TT_TRAIT_NAME, _dc_imp) : public boost::false_type {};
template <class T, class U>
struct BOOST_JOIN(BOOST_TT_TRAIT_NAME, _dc_imp)<T, U, typename boost::make_void<decltype(std::declval<typename add_reference<T>::type>() BOOST_TT_TRAIT_OP std::declval<typename add_reference<U>::type>())>::type>
: public boost::true_type {};
}
template <class T, class U = T, class Ret = boost::binary_op_detail::dont_care>
struct BOOST_TT_TRAIT_NAME : public boost::binary_op_detail:: BOOST_JOIN(BOOST_TT_TRAIT_NAME, _ret_imp) <T, U, Ret> {};
template <class T, class U>
struct BOOST_TT_TRAIT_NAME<T, U, void> : public boost::binary_op_detail:: BOOST_JOIN(BOOST_TT_TRAIT_NAME, _void_imp) <T, U> {};
template <class T, class U>
struct BOOST_TT_TRAIT_NAME<T, U, boost::binary_op_detail::dont_care> : public boost::binary_op_detail:: BOOST_JOIN(BOOST_TT_TRAIT_NAME, _dc_imp) <T, U> {};
}
#else
#include <boost/type_traits/detail/yes_no_type.hpp>
#include <boost/type_traits/integral_constant.hpp>
#include <boost/type_traits/is_base_of.hpp>
#include <boost/type_traits/is_const.hpp>
#include <boost/type_traits/is_convertible.hpp>
#include <boost/type_traits/is_fundamental.hpp>
#include <boost/type_traits/is_integral.hpp>
#include <boost/type_traits/is_pointer.hpp>
#include <boost/type_traits/is_same.hpp>
#include <boost/type_traits/is_void.hpp>
#include <boost/type_traits/remove_cv.hpp>
#include <boost/type_traits/remove_pointer.hpp>
#include <boost/type_traits/remove_reference.hpp>
#include <boost/type_traits/detail/is_likely_lambda.hpp>
namespace boost {
namespace detail {
// This namespace ensures that argument-dependent name lookup does not mess things up.
namespace BOOST_JOIN(BOOST_TT_TRAIT_NAME,_impl) {
// 1. a function to have an instance of type T without requiring T to be default
// constructible
template <typename T> T &make();
// 2. we provide our operator definition for types that do not have one already
// a type returned from operator BOOST_TT_TRAIT_OP when no such operator is
// found in the type's own namespace (our own operator is used) so that we have
// a means to know that our operator was used
struct no_operator { };
// this class allows implicit conversions and makes the following operator
// definition less-preferred than any other such operators that might be found
// via argument-dependent name lookup
struct any { template <class T> any(T const&); };
// when operator BOOST_TT_TRAIT_OP is not available, this one is used
no_operator operator BOOST_TT_TRAIT_OP (const any&, const any&);
// 3. checks if the operator returns void or not
// conditions: Lhs!=void and Rhs!=void
// we first redefine "operator," so that we have no compilation error if
// operator BOOST_TT_TRAIT_OP returns void and we can use the return type of
// (lhs BOOST_TT_TRAIT_OP rhs, returns_void_t()) to deduce if
// operator BOOST_TT_TRAIT_OP returns void or not:
// - operator BOOST_TT_TRAIT_OP returns void -> (lhs BOOST_TT_TRAIT_OP rhs, returns_void_t()) returns returns_void_t
// - operator BOOST_TT_TRAIT_OP returns !=void -> (lhs BOOST_TT_TRAIT_OP rhs, returns_void_t()) returns int
struct returns_void_t { };
template <typename T> int operator,(const T&, returns_void_t);
template <typename T> int operator,(const volatile T&, returns_void_t);
// this intermediate trait has member value of type bool:
// - value==true -> operator BOOST_TT_TRAIT_OP returns void
// - value==false -> operator BOOST_TT_TRAIT_OP does not return void
template < typename Lhs, typename Rhs >
struct operator_returns_void {
// overloads of function returns_void make the difference
// yes_type and no_type have different size by construction
static ::boost::type_traits::yes_type returns_void(returns_void_t);
static ::boost::type_traits::no_type returns_void(int);
BOOST_STATIC_CONSTANT(bool, value = (sizeof(::boost::type_traits::yes_type)==sizeof(returns_void((make<Lhs>() BOOST_TT_TRAIT_OP make<Rhs>(),returns_void_t())))));
};
// 4. checks if the return type is Ret or Ret==dont_care
// conditions: Lhs!=void and Rhs!=void
struct dont_care { };
template < typename Lhs, typename Rhs, typename Ret, bool Returns_void >
struct operator_returns_Ret;
template < typename Lhs, typename Rhs >
struct operator_returns_Ret < Lhs, Rhs, dont_care, true > {
BOOST_STATIC_CONSTANT(bool, value = true);
};
template < typename Lhs, typename Rhs >
struct operator_returns_Ret < Lhs, Rhs, dont_care, false > {
BOOST_STATIC_CONSTANT(bool, value = true);
};
template < typename Lhs, typename Rhs >
struct operator_returns_Ret < Lhs, Rhs, void, true > {
BOOST_STATIC_CONSTANT(bool, value = true);
};
template < typename Lhs, typename Rhs >
struct operator_returns_Ret < Lhs, Rhs, void, false > {
BOOST_STATIC_CONSTANT(bool, value = false);
};
template < typename Lhs, typename Rhs, typename Ret >
struct operator_returns_Ret < Lhs, Rhs, Ret, true > {
BOOST_STATIC_CONSTANT(bool, value = false);
};
// otherwise checks if it is convertible to Ret using the sizeof trick
// based on overload resolution
// condition: Ret!=void and Ret!=dont_care and the operator does not return void
template < typename Lhs, typename Rhs, typename Ret >
struct operator_returns_Ret < Lhs, Rhs, Ret, false > {
static ::boost::type_traits::yes_type is_convertible_to_Ret(Ret); // this version is preferred for types convertible to Ret
static ::boost::type_traits::no_type is_convertible_to_Ret(...); // this version is used otherwise
BOOST_STATIC_CONSTANT(bool, value = (sizeof(is_convertible_to_Ret(make<Lhs>() BOOST_TT_TRAIT_OP make<Rhs>()))==sizeof(::boost::type_traits::yes_type)));
};
// 5. checks for operator existence
// condition: Lhs!=void and Rhs!=void
// checks if our definition of operator BOOST_TT_TRAIT_OP is used or an other
// existing one;
// this is done with redefinition of "operator," that returns no_operator or has_operator
struct has_operator { };
no_operator operator,(no_operator, has_operator);
template < typename Lhs, typename Rhs >
struct operator_exists {
static ::boost::type_traits::yes_type s_check(has_operator); // this version is preferred when operator exists
static ::boost::type_traits::no_type s_check(no_operator); // this version is used otherwise
BOOST_STATIC_CONSTANT(bool, value = (sizeof(s_check(((make<Lhs>() BOOST_TT_TRAIT_OP make<Rhs>()),make<has_operator>())))==sizeof(::boost::type_traits::yes_type)));
};
// 6. main trait: to avoid any compilation error, this class behaves
// differently when operator BOOST_TT_TRAIT_OP(Lhs, Rhs) is forbidden by the
// standard.
// Forbidden_if is a bool that is:
// - true when the operator BOOST_TT_TRAIT_OP(Lhs, Rhs) is forbidden by the standard
// (would yield compilation error if used)
// - false otherwise
template < typename Lhs, typename Rhs, typename Ret, bool Forbidden_if >
struct trait_impl1;
template < typename Lhs, typename Rhs, typename Ret >
struct trait_impl1 < Lhs, Rhs, Ret, true > {
BOOST_STATIC_CONSTANT(bool, value = false);
};
template < typename Lhs, typename Rhs, typename Ret >
struct trait_impl1 < Lhs, Rhs, Ret, false > {
BOOST_STATIC_CONSTANT(bool,
value = (operator_exists < Lhs, Rhs >::value && operator_returns_Ret < Lhs, Rhs, Ret, operator_returns_void < Lhs, Rhs >::value >::value));
};
// some specializations needs to be declared for the special void case
template < typename Rhs, typename Ret >
struct trait_impl1 < void, Rhs, Ret, false > {
BOOST_STATIC_CONSTANT(bool, value = false);
};
template < typename Lhs, typename Ret >
struct trait_impl1 < Lhs, void, Ret, false > {
BOOST_STATIC_CONSTANT(bool, value = false);
};
template < typename Ret >
struct trait_impl1 < void, void, Ret, false > {
BOOST_STATIC_CONSTANT(bool, value = false);
};
// defines some typedef for convenience
template < typename Lhs, typename Rhs, typename Ret >
struct trait_impl {
typedef typename ::boost::remove_reference<Lhs>::type Lhs_noref;
typedef typename ::boost::remove_reference<Rhs>::type Rhs_noref;
typedef typename ::boost::remove_cv<Lhs_noref>::type Lhs_nocv;
typedef typename ::boost::remove_cv<Rhs_noref>::type Rhs_nocv;
typedef typename ::boost::remove_cv< typename ::boost::remove_reference< typename ::boost::remove_pointer<Lhs_noref>::type >::type >::type Lhs_noptr;
typedef typename ::boost::remove_cv< typename ::boost::remove_reference< typename ::boost::remove_pointer<Rhs_noref>::type >::type >::type Rhs_noptr;
BOOST_STATIC_CONSTANT(bool, value = (trait_impl1 < Lhs_noref, Rhs_noref, Ret, BOOST_TT_FORBIDDEN_IF >::value));
};
} // namespace impl
} // namespace detail
// this is the accessible definition of the trait to end user
template <class Lhs, class Rhs=Lhs, class Ret=::boost::detail::BOOST_JOIN(BOOST_TT_TRAIT_NAME,_impl)::dont_care>
struct BOOST_TT_TRAIT_NAME : public integral_constant<bool, (::boost::detail::BOOST_JOIN(BOOST_TT_TRAIT_NAME, _impl)::trait_impl < Lhs, Rhs, Ret >::value)>{};
} // namespace boost
#endif
#if defined(BOOST_MSVC)
# pragma warning ( pop )
#endif