dylint

incorrect_matches_operation

What it does

Checks for inefficient or incorrect use of the matches! macro. Examples of inefficient or boiler plate uses:

Examples of incorrect uses (the condition is probably always false):

Why is this bad?

One should use matches!(obj, case1 | case2) instead.

Known problems

Since we use a pre-expansion-lint, we match the matches! argument tokens. This is not ideal since we don’t know if the argument is a variable name or, e.g., a call. If it is a call, this lint may result in a false positive, though I bet there won’t be many of those.

Example

fn main() {
    let x = 1;
    if matches!(x, 123) | matches!(x, 256) {
        println!("Matches");
    }
}

Use instead:

fn main() {
    let x = 1;
    if matches!(x, 123 | 256) {
        println!("Matches");
    }
}
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