rust/src/test/run-pass/issue-2633.rs

class cat {
    let mut meow: fn@();
    new() { self.meow = fn@() { #error("meow"); };}
}

type kitty_info = {kitty: cat};

// Code compiles and runs successfully if we add a + before the first arg
fn nyan(kitty: cat, _kitty_info: kitty_info) {
    kitty.meow();
}

fn main() {
    let mut kitty = cat();
    nyan(kitty, {kitty: kitty});
}