into_option.rs

#![allow(unused_variables)]

// A bit more typing for the API author.
// (Sadly, the parameters need to be specified individually – or Rust would
// infer the concrete type from the first parameter given. This reads not as
// nicely, and documentation might not look as pretty as before.)
fn foo<I, D, S>(lorem: &str, ipsum: I, dolor: D, sit: S) where
    I: Into<Option<i32>>,
    D: Into<Option<i32>>,
    S: Into<Option<i32>>,
{
    println!("{}", lorem);
}

fn main() {
    foo("bar", None, None, None); // Still weird
    foo("bar", 42, None, None);   // Okay
    foo("bar", 42, 1337, -1);     // Wow, that's nice! Gimme more APIs like this!
}