[Bug libstdc++/77395] [6/7 Regression] std::is_constructible is false for type constructible via implicit conversion operator affecting std::tuple

[ville.voutilainen at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77395

--- Comment #2 from Ville Voutilainen <ville.voutilainen at gmail dot com> ---
Right, patch available at
https://gcc.gnu.org/ml/gcc-patches/2016-08/msg01983.html

Currently fixing negative test failures for it...