Rust field-level input validation with error list

#[derive(Debug)]
struct Signup {
    email: String,
    age: u8,
    password: String,
}

fn validate(s: &Signup) -> Result<(), Vec<(&'static str, String)>> {
    let mut errors = Vec::new();
    if !s.email.contains('@') {
        errors.push(("email", "must contain @".into()));
    }
    if s.age < 13 {
        errors.push(("age", "must be 13 or older".into()));
    }
    if s.password.len() < 8 {
        errors.push(("password", "must be at least 8 characters".into()));
    }
    if errors.is_empty() { Ok(()) } else { Err(errors) }
}