original.name="Subtype_Valid_5"
======
>>> main.whiley


type nat is (int x) where x > 0

type tup is ({nat f, int g} r) where r.g > r.f

type arr is (tup[] xs) where some { i in 0..|xs| | xs[i].f == 1 }

public export method test() :
    arr x = [{f: 1, g: 3}, {f: 1, g: 8}]
    x[0].f = 2
    assume x == [{f: 2, g: 3}, {f: 1, g: 8}]

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