? with non-result

help
1

Consider I have a fn that returns a String:

fn do_things() -> String {
    let res1 = match do_other_thing() {
        Ok(res) => res,
        Err(e) => return format!("do_other_thing failed because {}", e)
    }

    let res2 = match do_other_thing_2(&res1) {
        Ok(res) => res,
        Err(e) => return format!("do_other_thing_2 failed because {}", e)
    }

    format!("well done: {}", res2)
}

Here I cannot use Result as a return type because fn signature is dictated by the framework.
So I want to collapse Result<String, String> to String on error.

Can I somehow make "?" sign return String instead of Result?
Like this:

fn do_things() -> String {
    let res1 = do_other_thing().map_err(|e| format!("do_other_thing failed because {}", e))?;

    let res2 = do_other_thing_2(&res1).map_err(|e| format!("do_other_thing_2 failed because {}", e))?;

    format!("well done: {}", res2)
}
2

You can introduce a wrapper function with the inner one returning result and the outer one handling it.

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3

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