[Bug libstdc++/85965] [8/9 Regression] G++ gives cryptic error instead of incomplete type

[psmith at gnu dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85965

--- Comment #4 from Paul Smith <psmith at gnu dot org> ---
Oops sorry: I guess I'm not familiar enough with the vagaries of the bug
trackers :).  Thanks Jonathan!