[Bug fortran/53576] Very unhelpful error message: "Unclassifiable statement" instead of "Can't convert TYPE to ..."

[dominiq at lps dot ens.fr]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53576

--- Comment #2 from Dominique d'Humieres <dominiq at lps dot ens.fr> ---
I get the error

Error: Can't convert TYPE(amn_t) to COMPLEX(4) at (1)

if I replace amn%nsites in

  do jj = 1, amn%nsites

with a constant value (tested 0 and 5).