Extend manual_is_variant_and lint to check for boolean map comparisons

[GuillaumeGomez]

Fixes #14542.

changelog: [manual_is_variant_and]: Extend to check for boolean map comparisons

r? @samueltardieu

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r? @blyxyas

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[GuillaumeGomez]

Fixed fmt

[GuillaumeGomez]

Let's reroll reviewer.

r? clippy

[GuillaumeGomez]

r? samueltardieu

[samueltardieu]

This can probably be simplified quite a bit, see inner comment.

Could you please also add a test with a generic type which takes a generic parameter such as bool and implements a map(), so that we can check that types are correctly filtered?

[samueltardieu]

Could you also add a test where the left, ==/!= and right expressions come from different contexts? I think you would need to check that they are all in the same context as expr.

[GuillaumeGomez]

Just thought about a case where we're comparing to a function returned value. In this case we don't want to lint so I strengthened the check to cover this case.

I also added macro check, not sure if it's what you had in mind though?

[samueltardieu]

In the following tests:

macro_rules! mac {
    (some $e:expr) => { Some($e) };
    (some_map $e:expr) => { Some($e).map(|x| x % 2 == 0) };
    (map $e:expr) => { $e.map(|x| x % 2 == 0) };
    (eq $a:expr, $b:expr) => { $a == $b };
}

    let _ = mac!(some 2).map(|x| x % 2 == 0) == Some(true);
    let _ = mac!(some_map 2) == Some(true);
    let _ = mac!(map Some(2)) == Some(true);
    let _ = mac!(eq Some(2).map(|x| x % 2 == 0), Some(true));

the latest seems to fail. It should not lint when the equality operator comes from expansion. Comparing the contexts and parent_expr and expr should be enough to fix this.

Also, could you please merge your tests into manual_is_variant_and.rs rather than creating a new test file?

[GuillaumeGomez]

Sure, done!