lint suggestion: `needless_lifetimes` in `impl<'a>`

[thetayloredman]

What it does

needless_lifetimes currently could support suggesting lifetime elison in impl<'a> T<'a> or impl<'a> Trait for T<'a> signatures.

Advantage

Adds extra verbosity which is not necessary. If we elide lifetimes everywhere else, why don't we suggest it here?

Drawbacks

Unsure if there is any.

Example

impl<'a> MyType<'a> {
    // method definitions that don't reference 'a
}

Could be written as:

impl MyType<'_> {
    // method definitions that don't reference 'a
}

[PartiallyUntyped]

Given that I am in the process of cleaning up needless_lifetimes, I will pick this up.

@rustbot claim

[y21]

This was implemented in #13286

[joshka]

I think this was missed from the changelog