warning: unused imports: `collections::*`, `mem::*`
 --> /w/foo.rs:1:44
  |
1 | use std::{iter::*, io::{self, prelude::*}, mem::*, collections::*};
  |                                            ^^^^^^  ^^^^^^^^^^^^^^
  |
  = note: `#[warn(unused_imports)]` on by default

warning: 1 warning emitted

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