? operator, but for functions that don't return Result

help
9

This isn't quite right, but it did give me the confidence to write the macro I do want.

As I mentioned above, ? is brilliant because it will either return the unwrapped Ok() value for me to use or transfer control out of the function. I want something I can use inside the outer function (that forms the C API) as I translate from the Rust API, so I don't want to map final error codes, but have something that I can repeatedly use to extract "good" results or to bail with if things go wrong.

The C-like thing to do is (not always but commonly) to always return some Status enum and passing pointers for output. So I don't really want the macro/mapper to map anything to Status::Success; that's for the outer function to do when it thinks things have gone well.

This does what I want, I think.

The key thing is my modification of your wrapper, and the From function.

macro_rules! unwrap_or_return {
    ($expr:expr) => {
        match $expr {
            Ok(v) => v,
            Err(e) => {
                return e.into();
            }
        }
    };
}