=====
>>> main.whiley
property inc(int i) -> (int v)
requires i:
   return i + 1

public export method test():
   assert inc(-1) == 0
   assert inc(0) == 1
   assert inc(1) == 2
---
E400 main.whiley 2,9
=====
>>> main.whiley 2:3
requires i >= 0:
---
E700 main.whiley 6,10:16
=====
>>> main.whiley 6:7
---