Lint Suggestion: reimplementing .and_then with Some(x?)

[NoraCodes]

What it does

Suggest option.and_then(|value| value.inner_option) instead of option.and_then(|value| Some(value.inner_option?))

Categories (optional)

• Kind: style or complexity

What is the advantage of the recommended code over the original code

There's no reason to take an option, wrap it in another option, and use ? to short-circuit. and_then will work fine without it, and it's needlessly difficult to read.

Drawbacks

None.

Example

struct Outer {
    inner: Option<String>
}

let a = Some(Outer { inner: Some("hello".into()) });
a.and_then(|a| Some(a.inner?))

Could be written as:

struct Outer {
    inner: Option<String>
}

let a = Some(Outer { inner: Some("hello".into()) });
a.and_then(|a| a.inner)

[camsteffen]

Nice. This can include any case of return Some(option?) or return Ok(result?). Maybe call it needless_question_mark.

[bengsparks]

If no one has attempted this yet, I'd like to give it a shot.

[bengsparks]

Ok, so let me see if I've understood this correctly.

What needs to be recognized;
Option<T> and Result<T, E>, i.e. types for which the question mark operator are implemented for.

How can it be matched:
By matching Some(instance_of_option?) and Ok(instance_of_result?).

What help can be suggested:
The instance_of_* parameter be kept and the rest discarded.

Have I overseen anything?

[ghost]

You have to worry about the early exit of ?. This is probably only applicable on the last expression of a body or in a return statement.

[bengsparks]

Ok, I think I've got it done. I'll go open a PR.