Fix bug #5019 (looping zify on dependent types)

This fixes [bug #5019](https://coq.inria.fr/bugs/show_bug.cgi?id=5019),
"[zify] loops on dependent types"; before, we would see a `Z.of_nat (S
?k)` which could not be turned into `Z.succ (Z.of_nat k)`, add a
hypothesis of the shape `0 <= Z.of_nat (S k)`, turn that into a
hypothesis of the shape `0 <= Z.succ (Z.of_nat k)`, and loop forever on
this.

This may not be the "right" fix (there may be cases where `zify` should
succeed where it still fails with this change), but this is a pure
bugfix in the sense that the only places where it changes the behavior
of `zify` are the places where, previously, `zify` looped forever.

0 files changed, 0 insertions, 0 deletions