[Bug c++/100205] [11/12 Regression] error: invalid use of non-static data member

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100205

--- Comment #8 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #7)
> (I think GCC is correct)

clang9 accepts your reduced testcase.