func preconditionNotNone<T>(_ x: T?, _ message: @autoclosure () -> String = "", file: StaticString = #file, line: UInt = #line) -> T { precondition(x != nil, message, file: file, line: line) return x! }func preconditionNotNone<T>(_ x: T?, _ message: @autoclosure () -> String = "", file: StaticString = #file, line: UInt = #line) -> T { precondition(x != nil, message, file: file, line: line) return x! }! も消えるか。