[Bug fortran/98573] Dynamic type lost on assignment

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98573

--- Comment #8 from Paul Thomas <pault at gcc dot gnu.org> ---
(In reply to Dominique d'Humieres from comment #7)
> A patch has been submitted at
> 
> https://gcc.gnu.org/pipermail/fortran/2021-January/055624.html
> 
> and approved at
> 
> https://gcc.gnu.org/pipermail/fortran/2021-January/055644.html
> 
> More comments at
> 
> https://gcc.gnu.org/pipermail/fortran/2021-January/055651.html

For some reason that I do not recall, Tobias's comments caused me to pause and
then forget about this PR. The test that he suggested compiles and runs without
problem, as it does with allocate on assign.

The patch still applies and regtests OK, so I will bot apply it to mainline and
then back-port it.

Paul