Perhaps this match_bool case could be considered idiomatic?

[swfsql]

Hello, I have a suggestion for the match_bool lint
https://rust-lang.github.io/rust-clippy/master/index.html#match_bool

I'm not sure if this is idiomatic, buy I often attach (@) matched values into variables, eg.:

match some_hash_set.insert(some_key) {
        _previously_unset @ true => (),
        _previously_unset @ false => {
                 panic!("D'oh!")
        }
}

I actually prefer reading this interface like this, because I can kind of simultaneously see both branches (the "total" effect of each branch) and I kind of know beforehand that such value (_previously_unset) won't be used anywhere else, for anything else.

---

The "literal" translation for the if-else case would be:

{ // inner scope
        let previously_unset = some_hash_set.insert(some_key);
        if (!previously_unset) {
                panic!("D'oh!")
        }
}

But in this case, to see the "total" effect of previously_unset @ true, I'd have to look past the if statement and see where the variable would still be used (in which, in this case, would be nowhere.. since the scope ended).

---

Both cases have 6 lines, and the first one is slightly more verbose. But I actually am more comfortable at reasoning about the first case - it feels familiar, as if the function returned an enum of two cases..

so... this is a suggestion and perhaps you could agree with!
Thanks in advance,

[oli-obk]

I think we could prevent the lint from triggering if there are bindings bound on the arms.

Although I personally still prefer

if !some_hash_set.insert(some_key) {
    panic!("D'oh!");
}

[swfsql]

Oh wait, I just noted that one can also do:

if let _previously_unset @ false = some_hash_set.insert(some_key) {
    panic!("D'oh!");
}

which has all the benefits!
(not that verbose; easy to infer effects; named values), (and passes on clippy!)

---

So perhaps this (if-let) could also be a suggestion instead (for someone matching on bools)?

Following the suggestion format (from https://rust-lang.github.io/rust-clippy/master/index.html#match_bool )

if let _condition @ true = true {
    foo();
} else {
    bar();
}

---

Thanks for the clear and quick response!

[camsteffen]

I think it's quite unusual to use _name @ just for code clarity rather than just doing let name =.