[Bug libstdc++/110853] [13/14/15/16 Regression] Bad interaction between deduction guide with decay and constraints (CTAD, std::pair and function lvalue)

[ppalka at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110853

--- Comment #6 from Patrick Palka <ppalka at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #5)
> This is a regression caused by the new concepts-based constructor
> constraints in gcc 12.
And the analogous std::tuple example started failing after r13-54 (with
-std=c++17).