[Bug ada/126928] New: Assert_Failure or Storage_Error from using far too many layers of generics

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126928

            Bug ID: 126928
           Summary: Assert_Failure or Storage_Error from using far too
                    many layers of generics
           Product: gcc
           Version: 16.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: ada
          Assignee: unassigned at gcc dot gnu.org
          Reporter: liam at liampwll dot com
                CC: dkm at gcc dot gnu.org
  Target Milestone: ---

Created attachment 65357
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=65357&action=edit
reproducer

This is once again extracted from code in https://github.com/Prunt3D/prunt that
has not been pushed yet. However, this time I have tested on a clean compiler
build. It causes an ICE on both 16 and 17.

Once again I let a LLM figure out the reproducer. It also gave me an
explanation that sounds plausible for the cause but it's in parts of the
compiler that I don't understand very well so I won't post it here unless
someone is interested in reading an analysis that could be completely wrong.