Unnecessary match sub-argument lint

What it does

Clippy could spot situations similar to this one, where the second input (b) is unnecessary.

This is a very simple example, easy to spot visually. Clippy should be able to spot all similar situations.

Lint Name

unnecessary_match_argument

Category

suspicious

Advantage

No response

Drawbacks

No response

Example

fn test1(a: bool, b: bool) -> u32 {
    match (a, b) {
        (true, true) => 1,
        (true, false) => 1,
        (false, true) => 2,
        (false, false) => 2,
    }
}

test1 is equivalent to test2:

fn test2(a: bool, b: bool) -> u32 {
    match a {
        true => 1,
        false => 2,
    }
}

There are more complex situations that I am less sure are worth creating lints for. In this match the the first item of the 2-tuple output depends only of the first item of the 2-tuple input. And the same is true for the second inputs and outputs. So this match could be decomposed into two simpler and smaller matches.

fn test3(a: bool, b: bool) -> (bool, bool) {
    match (a, b) {
        (true, true) => (false, true),
        (true, false) => (false, false),
        (false, true) => (true, true),
        (false, false) => (true, false),
    }
}

(Ideas from: https://www.hillelwayne.com/post/decision-table-patterns/ ).

Start with the issue's test1 and test2 examples and determine the intended scope of the unnecessary_match_argument lint. No implementation files, tests, or entry points are named; identify the relevant Clippy lint and test locations, then define completion as detecting the stated unnecessary match argument without overreaching into the more complex test3 idea.