Traits for ??

[jD91mZM2]

I sadly barely get to use ?, because I find myself not using Result<> as often because it just doesn't fit in. For example, I instead return a struct with a success boolean at one point, or I wanna completely ignore errors the other. There should be a way for ? to detect return values and use some trait to return an error.

For example:

struct Stuff {
    // some fields here
    success: bool
}

impl Try for Stuff {
    fn err(error: std::error::Error) -> Stuff {
        Stuff{
            // some fields here
            success: false;
        }
    }
}

Also, () return values would implement the trait as well, but return.. well... nothing.

If the suggestion sounds stupid to you - sorry for disturbing :(

[pnkfelix]

Can you clarify how your suggestion differs from existing (and accepted) RFC #1859, text here

[burdges]

Your examples sound like they map to Result easily enough. There are methods like map_err and ok_or on Result and Option for most issues that you might encounter.

If you want to find examples that do not always fit Result so well, then you should look at futures and the discussions around futures in the ? rfcs and tracking issues. In other words, your code returns a three+ state enum where what counts as an error may shift depending on usage, so maybe one needs some extra-ergonomic error mapping methods.

[jD91mZM2]

@pnkfelix is right. It's no different from that pull request.