anonymous — Fri, 25 Apr 2014 10:57:13 GMT

I should mention what error i get when compiling the test code. On clang++-3.4 with -std=c++11, I got:

clang++-mp-3.4 -std=c++11 -I /opt/local/include/ main.cpp
In file included from main.cpp:1:
In file included from /opt/local/include/boost/type_traits.hpp:65:
In file included from /opt/local/include/boost/type_traits/is_nothrow_move_assignable.hpp:22:
/opt/local/include/boost/utility/enable_if.hpp:40:25: error: no type named 'type' in 'boost::result_of<A (int)>'
   typedef typename T::type type;
           ~~~~~~~~~~~~^~~~
main.cpp:12:1: note: in instantiation of template class 'boost::lazy_enable_if_c<true, boost::result_of<A (int)> >'
     requested here
typename boost::lazy_enable_if_c<
^
main.cpp:16:1: note: while substituting explicitly-specified template arguments into function template 'test'
test(int){}
^
1 error generated.

owner, component changed

Andrey Semashev — Sat, 08 Jul 2017 20:37:35 GMT

owner changed from No-Maintainer to Peter Dimov
component utility → core

This might be useful. Deriving from T won't work if it is final, but in C++11 we could reformulate lazy_enable_if_c like this:

template< bool Cond, typename T >
using lazy_enable_if_c = typename enable_if_c< Cond, T >::type::type;

Boost C++ Libraries: Ticket #9953: lazy_enable_if is not sfinae friendly

owner, component changed