[Bug c++/127008] `if (type a(1))` should have a better error message

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127008

--- Comment #3 from Drea Pinski <pinskia at gcc dot gnu.org> ---
Note what I used in the end was:
if (long_mul_summand s{leaf})

https://gcc.gnu.org/cgit/gcc/commit/?id=7642bd333e47cb8de89094600f29decdf91456e7