use futures::stream::FuturesUnordered;
fn main() {

    let u = FuturesUnordered::new();
    
    u.push(async {});
    u.push(async {});
    
}

error[E0308]: mismatched types
  --> src/main.rs:12:18
   |
11 |     u.push(async {});
   |                  -- the expected generator
12 |     u.push(async {});
   |                  ^^ expected generator, found a different generator
   |
   = note: expected generator `[static generator@src/main.rs:11:18: 11:20]`
              found generator `[static generator@src/main.rs:12:18: 12:20]`