[Bug libstdc++/70845] [6/7 Regression] inherited piecewise_construct_t constructor from std::pair by "using-declarations" is missing

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70845

--- Comment #9 from Jonathan Wakely <redi at gcc dot gnu.org> ---
6.1.1 is not a release, it's the current development snapshot from the gcc-6
branch. It will be fixed in a later version.