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

[mpolacek at gcc dot gnu.org]

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

--- Comment #5 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Small test from Hana:

void foo([[maybe_unused]] int a) { }

struct bar {
    bar([[maybe_unused]] int a) { }
};