@swift-5.3.3
func modify<T>(_ t: inout T, _ f: (inout T) -> Void) { f(&t) } protocol P { var a: Int { get set } var b: Int { get set } } struct S: P { var a: Int = 3 var b: Int = 1 } var s = S() func foo<T: P>(_ s: inout T) { modify(&s) { (s) in modify(&s.a) { (a) in modify(&s.b) { (b) in a = a + b b = a - b } } } print(s) } foo(&s)
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