New Lint: Explicit ranges with p0 | ... | p_n => range pat

[Centril]

Category: Complexity

Consider:

match x {
    1 | 2 | 4 | 3 => 0,
     _ => 1,
}

Ostensibly the or-pattern would be more clearly written as 1..=4.

I would suggest making the analysis on HAIR.

cc @oli-obk cc rust-lang/rust#67488

[ghost]

I thought HAIR was something used internally by the MIR crates. How do you access it from a lint?

[Centril]

Not sure; HIR probably works as well but is less desugared.