tokio: remove wildcard in match pattern

[wathenjiang]

When we use wildcard * in match pattern, it can lead to potential errors.

enum MyEnum{
    TypeA,
    TypeB,
    TypeC,
}

fn logic(e :MyEnum){
    use MyEnum::*;

    match e {
        TypeA =>  println!("A"),
        TypeB =>  println!("B"),
        TypeC =>  println!("C"),
    }
}

If we delete TypeC，add add TypeD

enum MyEnum{
    TypeA,
    TypeB,
    TypeD,
}

fn logic(e :MyEnum){
    use MyEnum::*;

    match e {
        TypeA =>  println!("A"),
        TypeB =>  println!("B"),
        TypeC =>  println!("C"),
    }
}

The Rust compiler takes TypeC as a named variables, not a variant of the enum, and the unexpected error occurs.

So we should never use such as use MyEnum::*; wildcard in Rust code.

[Darksonn]

That would trigger a warning because TypeC is not snake case, which would fail our build.

[wathenjiang]

That would trigger a warning because TypeC is not snake case, which would fail our build.

Yes, the CI is useful for it. But if we do this, we can avoid such error before CI, and it may have better code smell.

[Darksonn]

I don't mind dropping the import for this case, but I don't want to drop it for Poll, Result, Ok, or Ordering. That's too much noise.

[wathenjiang]

I don't mind dropping the import for this case, but I don't want to drop it for Poll, Result, Ok, or Ordering. That's too much noise.

Some kinds of enum of them, such as Result, Ordering might not be changed in the future, unless the std of rust make some broken changes. I reserve my opinion on these enums. But I believe some enums which is defiend in internal code of tokio might change in the future.

We can use use MyEnum as E to reduce the noise.

[wathenjiang]

I have made some changes, allowing the wildcard in Result and Ordering for reduce the noise. And keep the other changes.

[Darksonn]

Why E? Should this not be a K for kind?

I'm also okay with TryCurrentErrorKind:: here.

[wathenjiang]

E means Error, and I may have been influenced by golang :). I believe in Rust the error have a kind, which can refer to: https://doc.rust-lang.org/std/io/enum.ErrorKind.html, and the use of TryCurrentErrorKind :: here is not tedious, so let us just use TryCurrentErrorKind ::.

[wathenjiang]

The CI has passed, it looked like the last CI gone wrong.

[Darksonn]

Thanks.