[Bug c++/96120] Ambiguity diagnostic message of "invalid use of type 'void' in parameter declaration"

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96120

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Haoxin Tu from comment #0)
> GCC might emit the ambiguity diagnostic message on it.

What does that mean?