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Fix handling of no argument functions in C++11.

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When they don't exist it was failing because result_of doesn't have a
type and SFINAE couldn't be used as they have no template arguments.
This commit is contained in:
Daniel James
2016-05-27 08:38:01 +01:00
parent f2e4a80a33
commit a43bbfe34c
2 changed files with 62 additions and 4 deletions
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31
include/boost/functional/forward_adapter.hpp
View File

@@ -144,8 +144,30 @@ namespace boost
: boost::result_of< BOOST_DEDUCED_TYPENAME c<Self>::t() >
{ };
// WHen operator()() doesn't have any parameters, it can't
// be templatized and can't use SFINAE, so intead use class
// template parameter SFINAE to decide whether to instantiate it.
template <typename T, typename R = void>
struct forward_adapter_sfinae
{
typedef T type;
};
// This is the fallback for when there isn't an operator()(),
// need to create an operator() that will never instantiate
// so that using parent::operator() will work okay.
template< class MD, class F, class FC, class Enable = void>
struct forward_adapter_impl_zero
{
template <typename T> struct never_instantiate {};
template <typename T>
typename never_instantiate<T>::type operator()(T) const {}
};
template< class MD, class F, class FC>
struct forward_adapter_impl<MD,F,FC,0,0>
struct forward_adapter_impl_zero<MD, F, FC,
typename forward_adapter_sfinae<typename boost::result_of< FC() >::type>::type>
{
inline typename boost::result_of< FC() >::type
operator()() const
@@ -158,6 +180,13 @@ namespace boost
{
return static_cast<MD*>(this)->target_function()();
}
};
template< class MD, class F, class FC >
struct forward_adapter_impl<MD,F,FC,0,0>
: forward_adapter_impl_zero<MD,F,FC>
{
using forward_adapter_impl_zero<MD,F,FC>::operator();
// closing brace gets generated by preprocessing code, below

31
include/boost/functional/lightweight_forward_adapter.hpp
View File

@@ -149,8 +149,31 @@ namespace boost
: boost::result_of< BOOST_DEDUCED_TYPENAME c<Self>::t() >
{ };
// When operator() doesn't have any parameters, it can't
// be templatized and can't use SFINAE, so intead use class
// template parameter SFINAE to decide whether to instantiate it.
template <typename T, typename R = void>
struct lightweight_forward_adapter_sfinae
{
typedef T type;
};
// This is the fallback for when there isn't an operator()(),
// need to create an operator() that will never instantiate
// so that using parent::operator() will work okay.
template< class MD, class F, class FC, class Enable = void>
struct lightweight_forward_adapter_impl_zero
: lightweight_forward_adapter_result
{
template <typename T> struct never_instantiate {};
template <typename T>
typename never_instantiate<T>::type operator()(T) const {}
};
template< class MD, class F, class FC>
struct lightweight_forward_adapter_impl<MD,F,FC,0,0>
struct lightweight_forward_adapter_impl_zero<MD, F, FC,
typename lightweight_forward_adapter_sfinae<typename boost::result_of< FC() >::type>::type>
: lightweight_forward_adapter_result
{
inline typename boost::result_of< FC() >::type
@@ -166,6 +189,12 @@ namespace boost
}
};
template< class MD, class F, class FC >
struct lightweight_forward_adapter_impl<MD,F,FC,0,0>
: lightweight_forward_adapter_impl_zero<MD,F,FC>
{
};
# define BOOST_PP_FILENAME_1 \
<boost/functional/lightweight_forward_adapter.hpp>
# define BOOST_PP_ITERATION_LIMITS \