[Bug c++/91742] User defined conversion references

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91742

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Diego from comment #0)
> I read through the c++17 standard and did not find any information about
> this behavior being implementation defined.

It's not implementation defined, but I think all implementations are required
to do what GCC 8 does (and other compilers agree).

The current behaviour started with r259123 (before that there  was an ICE,
introduced by r258755).