置換モデルでthrowsが純粋じゃないことを示す例

Impure.swift

enum Error: Swift.Error {
    case castError
}

func toInt(_ string: String) throws -> Int {
    guard let i = Int(string) else {
        throw Error.castError
    }
    return i
}



func myFunc() throws {
    let hoge = try toInt("123")

    do {
        let fuga = try toInt("123") + hoge
        print(fuga)
    }
    catch {
        print("^_^;")
    }
}