@swift-5.0.3 @swift-5.1.5 @swift-5.2.5 @swift-5.3.3 @swift-5.4.3 func test(_ callback: () -> Void) { let x = callback x() } https://forums.swift.org/t/an-odd-error-escaping-closure-captures-mutating-self/50118/10 (edited)