Lint unnecessary .into_iter() in function arguments

[yongqli]

What it does

If someone didn't know that various functions can take an impl IntoIterator instead of an impl Iterator for their arguments, they might have wrote useless explicit .into_iter()s.

See also #1094

Lint Name

explicit_into_iter_fn_arg

Category

pedantic

Advantage

No response

Drawbacks

No response

Example

fn main() {
    let mut v = vec![];
    v.extend(vec![0].into_iter());
}

Could be written as:

fn main() {
    let mut v = vec![];
    v.extend(vec![0]);
}

[y21]

@rustbot claim

I feel like instead of adding a new lint for this, we could just add it to the existing useless_conversion lint that you linked? Seems like another relevant case that it could handle
Edit: nevermind, I took a closer look at useless_conversion and it doesn't seem too related now that I think about it, so a new lint seems fine