fn main() {
    println!("{:?}", {
        (&[1, 2, 3]).iter().map(|x| x*2).sum::<usize>()
    });
}


/* ~~~~=== stderr ===~~~~
   Compiling playground v0.0.1 (file:///playground)
error[E0277]: the trait bound `usize: std::iter::Sum<i32>` is not satisfied
 --> src/main.rs:5:42
  |
5 |         (&[1, 2, 3]).iter().map(|x| x*2).sum::<usize>()
  |                                          ^^^ the trait `std::iter::Sum<i32>` is not implemented for `usize`
  |
  = help: the following implementations were found:
            <usize as std::iter::Sum<&'a usize>>
            <usize as std::iter::Sum>

error: aborting due to previous error

For more information about this error, try `rustc --explain E0277`.
error: Could not compile `playground`.

To learn more, run the command again with --verbose.

*/

/* ~~~~=== stdout ===~~~~

*/