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/*
@Copyright Barrett Adair 2015-2017
Distributed under the Boost Software License, Version 1.0.
(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
*/
#ifndef BOOST_CLBL_TRTS_HAS_VOID_RETURN_HPP
#define BOOST_CLBL_TRTS_HAS_VOID_RETURN_HPP
#include <boost/callable_traits/detail/core.hpp>
namespace boost { namespace callable_traits {
//[ has_void_return_hpp
/*`[section:ref_has_void_return has_void_return]
[heading Header]
``#include <boost/callable_traits/has_void_return.hpp>``
[heading Definition]
*/
// inherits from either std::true_type or std::false_type
template<typename T>
struct has_void_return;
//<-
template<typename T>
struct has_void_return
: std::is_same<typename detail::traits<
detail::shallow_decay<T>>::return_type, void> {};
#ifdef BOOST_CLBL_TRTS_DISABLE_VARIABLE_TEMPLATES
template<typename T>
struct has_void_return_v {
static_assert(std::is_same<T, detail::dummy>::value,
"Variable templates not supported on this compiler.");
};
#else
//->
// only available when variable templates are supported
template<typename T>
//<-
BOOST_CLBL_TRAITS_INLINE_VAR
//->
constexpr bool has_void_return_v = //see below
//<-
std::is_same<typename detail::traits<
detail::shallow_decay<T>>::return_type, void>::value;
#endif
}} // namespace boost::callable_traits
//->
/*`
[heading Constraints]
* none
[heading Behavior]
* `std::false_type` is inherited by `has_void_return<T>` and is aliased by `typename has_void_return<T>::type`, except when one of the following criteria is met, in which case `std::true_type` would be similarly inherited and aliased:
* `T` is a function, function pointer, or function reference where the function's return type is `void`.
* `T` is a pointer to a member function whose return type is `void`.
* `T` is a function object with a non-overloaded `operator()`, where the `operator()` function returns `void`.
* On compilers that support variable templates, `has_void_return_v<T>` is equivalent to `has_void_return<T>::value`.
[heading Input/Output Examples]
[table
[[`T`] [`has_void_return_v<T>`]]
[[`void()`] [`true`]]
[[`void(int) const`] [`true`]]
[[`void(* const &)()`] [`true`]]
[[`void(&)()`] [`true`]]
[[`void(foo::*)() const`] [`true`]]
[[`int(*)()`] [`false`]]
[[`int(*&)()`] [`false`]]
[[`int`] [`false`]]
[[`int foo::*`] [`false`]]
[[`void* foo::*`] [`false`]]
]
[heading Example Program]
[import ../example/has_void_return.cpp]
[has_void_return]
[endsect]
*/
//]
#endif
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