enum Exception: Error {
    case text
}

func throwIfTrue(_ param: Bool) throws {
    defer {
        print("defer")
    }
    do {
        if param {
            throw Exception.text
        }
    }
    catch {
        print("catch")
    }
} 

try! throwIfTrue(true)
//printed: "catch" and "defer"
try! throwIfTrue(false)
//printed only "defer"