#[derive(Debug)]
struct Email<'a>(&'a str);

#[derive(Debug)]
struct Postal<'a>(&'a str);

#[derive(Debug)]
struct Name<'a>(&'a str);

#[derive(Debug)]
enum ContactInfo<'a> {
    EmailOnly(Email<'a>),
    PostalOnly(Postal<'a>),
    EmailAndPostal(Email<'a>, Postal<'a>),
}

// allow `EmailOnly` instead of `ContactInfo::EmailOnly`
use self::ContactInfo::*;

#[derive(Debug)]
struct Contact<'a> {
    name: Name<'a>,
    contact_info: ContactInfo<'a>,
}

impl<'a> Contact<'a> {
    fn with_postal(self, postal: Postal<'a>) -> Self {
        let name = self.name;
        let contact_info = match self.contact_info {
            EmailOnly(email) => EmailAndPostal(email, postal),
            PostalOnly(_) => PostalOnly(postal),
            EmailAndPostal(email, _) => EmailAndPostal(email, postal),
        };

        Contact { name, contact_info }
    }
}

impl<'a> From<(Name<'a>, Postal<'a>)> for Contact<'a> {
    fn from(contact: (Name<'a>, Postal<'a>)) -> Self {
        let (name, postal) = contact;
        let contact_info = PostalOnly(postal);

        Contact { name, contact_info }
    }
}

impl<'a> From<(Name<'a>, Email<'a>)> for Contact<'a> {
    fn from(contact: (Name<'a>, Email<'a>)) -> Self {
        let (name, email) = contact;
        let contact_info = EmailOnly(email);

        Contact { name, contact_info }
    }
}

impl<'a> From<(Name<'a>, Email<'a>, Postal<'a>)> for Contact<'a> {
    fn from(contact: (Name<'a>, Email<'a>, Postal<'a>)) -> Self {
        let (name, email, postal) = contact;
        let contact_info = EmailAndPostal(email, postal);

        Contact { name, contact_info }
    }
}

fn main() {
    let name = "Bart Simpson";
    let postal = "742 Evergreen Terrace";
    let email = "bart@simpsons.fam";

    let postal_only = Contact::from((Name(name), Postal(postal)));
    println!("{:?}", postal_only);

    let email_only = Contact::from((Name(name), Email(email)));
    println!("{:?}", email_only);

    let email_and_postal = email_only.with_postal(Postal(postal));
    println!("{:?}", email_and_postal);

    let email_and_postal = Contact::from((Name(name), Email(email), Postal(postal)));
    println!("{:?}", email_and_postal);
}