=====
>>> main.whiley
method m(int i) -> (int r)
ensures i == r:
   return i

property inc(int i) -> (int v)
requires m(i) == i:
   return i + 1

public export method test():
   assert inc(-1) == 0
   assert inc(0) == 1
   assert inc(1) == 2
---
E608 main.whiley 6,9:12
=====
>>> main.whiley 1:2
function m(int i) -> (int r)
---