I’ve long been a proponent of having some sort of syntax in Rust for writing functions which return results which “ok-wrap” the happy path. This is has also always been a feature with very vocal, immediate, and even emotional opposition from many of our most enthusiastic users. I want to write, in one place, why I think this feature would be awesome and make Rust much better.

I don’t want to get into the details too much of the specific proposal, but here’s a sketch of one way this could work (there are a number of variables). We would add a syntactic modifier to the signature of a function, like this:

fn foo() -> usize throws io::Error {
    //..
}

This function returns Result<usize, io::Error>, but internally the return expressions return a value of type usize, not the Result type. They are “Ok-wrapped” into being Ok(usize) automatically by the language. If users wish to throw an error, a new throw expression is added which takes the error side (the type after throws in the signature). The ? operator would behave in this context the same way it behaves in a function that returns Result.