[Bug c++/87093] is_constructible (__is_constructible() instrinsic) explicitly instantiates conversion member function of source

[ville.voutilainen at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87093

--- Comment #4 from Ville Voutilainen <ville.voutilainen at gmail dot com> ---
Patch available: https://gcc.gnu.org/ml/gcc-patches/2018-09/msg00484.html