Ada subtypes and base types (was: Bootstrap failure on trunk: x86_64-linux-gnu)

[Richard Kenner]

     Which leaves us with a very fundamental issue.  Namely that we can not
     use TYPE_MIN_VALUE or TYPE_MAX_VALUE for ranges.  

The point is that it *is* supposed to be usable in general.  If it can't
be used in a specific case, let's address that specific case and understand
what needs fixing.  The intent is for it to be useful and usable information..