[Bug fortran/79854] diagnostics: gfc_conv_constant_to_tree should be gfc_internal_error

[dominiq at lps dot ens.fr]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79854

Dominique d'Humieres <dominiq at lps dot ens.fr> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2017-07-26
           Assignee|unassigned at gcc dot gnu.org      |dominiq at lps dot ens.fr
     Ever confirmed|0                           |1

--- Comment #1 from Dominique d'Humieres <dominiq at lps dot ens.fr> ---
AFAICT this internal error has never triggered. If someone can come with a test
for it, this would be nice.