fixes#24091, refs #24092
Any instantiations resolving to a generic body type now gives an error.
Due to #24092, this does not error in cases like matching against `type
M` in generics because generic body type symbols are just not
instantiated. But this prevents parameters with type `type M` from being
used, although there doesn't seem to be any code which does this. Just
in case such code exists, we still allow `typedesc` types resolving to
generic body types.
