WIP: New lint [`manual_position`]

[GabrielBFern]

Add a new lint to detect manual implementation of position() using enumerate().find(_)

changelog: Add new [manual_position] lint

fixes #2282

I need help handling this case when I need to change the deref on the body of the closure.

    let v = [1, 2, 3, 5, 6];
    let _ = v.iter().enumerate().find(|(_, ch)|**ch == 3).unwrap().0;
    // Right now, the lint is suggesting this (which does not compile):
    let _ = v.iter().position(|ch|**ch == 3).unwrap();
    // but i think i need to make like this:
    let _ = v.iter().position(|ch|*ch == 3).unwrap();
    // or this:
    let _ = v.iter().position(|&ch|ch == 3).unwrap();

[rustbot]

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[GabrielBFern]

I found this example. I think I need something similar, but I don't know how to create an expr from the closure suggestion I made to pass it to the deref_closure_args function. Or if I need to pass the original expr first to deref_closure_args, in this case, I cannot separate the arguments and the body of the closure.

[llogiq]

First, check whether the closure input pattern already does a deref (|&a| ..). If so, we just remove the deref. Otherwise, we can either avoid linting, lint without suggestion or walk through the closure body adding derefs to any ExprPath matching the input.

[J-ZhengLi]

Now here comes the triaging part, lol...

Hey @GabrielBFern, this is a ping from triage. There hasn't been any activity for some time, you're always welcome to ask questions (there's a zulip stream if you're interested). It's also fine if you don't have the time right now. We just want to check in and make sure that you're not stuck.

@rustbot author

[xFrednet]

Hey this is triage, I'm closing this due to inactivity. If you want to continue this implementation, you're welcome to create a new PR. Thank you for the time, you already put into this!

Interested parties are welcome to pick this implementation up as well :)

@rustbot label +S-inactive-closed -S-waiting-on-author -S-waiting-on-review