After initial compilation where the system is melted, a deferred
routine effected by an attribute is changed to a constant attribute.
When the VMFN error is reported, it is changed back to a deferred
routine and compilation finishes normally.  Then a new class with a
deferred version of the routine is inherited and called with dynamic
type Current.  After changes are melted, execution ends with a
segmentation fault.

Discovered in Release 5.0.015.