[Bug c++/81429] maybe_unused attribute triggers syntax error when used on first argument to a constructor

[rbock at eudoxos dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81429

--- Comment #10 from Roland B <rbock at eudoxos dot de> ---
(In reply to Marek Polacek from comment #9)
> Fixed on trunk, will backport to 9.3 later.

Thanks! Much appreciated :-)