func highFunc(_ f: () -> Void) { f() } func main() { var a: Int = 3 highFunc { [a] in a = 5 // Cannot assign to value: 'a' is an immutable capture } } (edited)func highFunc(_ f: () -> Void) { f() } func main() { var a: Int = 3 highFunc { [a] in a = 5 // Cannot assign to value: 'a' is an immutable capture } } (edited)