[Bug libstdc++/126949] [15/16/17 Regression] Can't construct an unordered set with a hasher whose ctor is explicit

[gnu.ojxq8 at dralias dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126949

--- Comment #4 from maic <gnu.ojxq8 at dralias dot com> ---
The default member init was likely left out to allow for C++11 aggregate init.
A new patch preserves that and was sent to
https://gcc.gnu.org/pipermail/libstdc++/2026-August/067660.html