There were a couple papers here -- including last minute fix due to breakage. This is probably the correct starting place:
removed for 26 at the last minute
https://isocpp.org/files/papers/P4144R0.html
This paper is to restore with the correct constraints
https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2026/p4190r0.html
There were a couple papers here -- including last minute fix due to breakage. This is probably the correct starting place:
removed for 26 at the last minute
https://isocpp.org/files/papers/P4144R0.html
This paper is to restore with the correct constraints
https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2026/p4190r0.html