IRCUser.hostmask

{
    const user = IRCUser("nickname", "ident", "address.tld");
    immutable hostmask = user.hostmask;
    assert((hostmask == "nickname!ident@address.tld"), hostmask);
}
{
    const user = IRCUser("nickname", string.init, "address.tld");
    immutable hostmask = user.hostmask;
    assert((hostmask == "nickname!*@address.tld"), hostmask);
}
{
    const user = IRCUser(string.init, string.init, "address.tld");
    immutable hostmask = user.hostmask;
    assert((hostmask == "*!*@address.tld"), hostmask);
}
{
    const IRCUser user;
    immutable hostmask = user.hostmask;
    assert((hostmask == "*!*@*"), hostmask);
}