4 ( $a:tt $b:tt ) => { println!("two tokens") };
8 ( $a:tt $b:tt $c:tt ) => { println!("three tokens") };
12 ( $a:tt $b:tt $c:tt $d:tt ) => { println!("four tokens") };
16 demo3!(foo#bar); //~ ERROR prefix `foo` is unknown
17 demo2!(foo"bar"); //~ ERROR prefix `foo` is unknown
18 demo2!(foo'b'); //~ ERROR prefix `foo` is unknown
20 demo2!(foo'b); //~ ERROR prefix `foo` is unknown
21 demo3!(foo# bar); //~ ERROR prefix `foo` is unknown
22 demo4!(foo#! bar); //~ ERROR prefix `foo` is unknown
23 demo4!(foo## bar); //~ ERROR prefix `foo` is unknown
26 //~^ ERROR prefix `foo` is unknown
27 //~| ERROR prefix `bar` is unknown