original.name="Function_Valid_4"
======
>>> main.whiley


type fr4nat is (int x) where x >= 0

function g(fr4nat x) -> fr4nat:
    return x + 1

function f(fr4nat x) -> int:
    return x

public export method test() :
    fr4nat y = 1
    assume f(g(y)) == 2

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