suggest using `if let Some(x) = arr.first()` over `if !arr.is_empty() then arr[0]`

[J-ZhengLi]

What it does

Well, exactly as the title described, and could apply to whiles as well.

The idea is kinda like a combination of [unnecessary_unwrap] and [get_first].

Such lint might already exist, idk.

Advantage

Readability?

Drawbacks

maybe? maybe not?

Example

if !seq.is_empty() {
    let x = seq[0];
    // ...
}

Could be written as:

if let Some(x) = seq.first() {
    // ...
}

[Jacherr]

@rustbot claim