[Bug fortran/93563] Wrong code makes the compiler hang

[dominiq at lps dot ens.fr]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93563

--- Comment #2 from Dominique d'Humieres <dominiq at lps dot ens.fr> ---
Gfortran 6.5 gives the error:

      class(TreeNode_t), dimension(:), allocatable :: children
                                                    1
Error: Derived type at (1) has not been previously defined and so cannot appear
in a derived type definition

After revision 241089 I get an ICE.