original.name="TypeEquals_Invalid_12"
js.execute.ignore=true
======
>>> main.whiley
function f(int|null x, int|null y) -> (int r)
ensures r == 0 || r == x:
    //
    x = y
    //
    if x is int && x >= 0:
        return x
    else:
        return 0

public export method test():
    assume f(0,0) == 0
    assume f(1,0) == 0
    assume f(0,1) == 1
---
E701 main.whiley 14,11:16
E717 main.whiley 7,8:15