相关疑难解决方法(0)

fn main() {
    foo().map_err(|err| println!("{:?}", err));
}

fn foo() -> Result<(), std::io::Error> {
    Ok(())
}

结果:

warning: unused `std::result::Result` that must be used
 --> src/main.rs:2:5
  |
2 |     foo().map_err(|err| println!("{:?}", err));
  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: #[warn(unused_must_use)] on by default
  = note: this `Result` may be an `Err` variant, which should be handled

    Finished dev [unoptimized + debuginfo] target(s) in 0.58s
     Running `target/debug/playground`

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