As the kind of more conservative Rust user GP references, I've had a great time with the derive_more crate's From derive [0].

This lets me write code like this:

    #[derive(From, Debug)]
    pub enum SomeSpecificError {
        Io(io::Error),
        SomeAppLevelErrorCondition,
    }

    fn do_something() -> Result<(), SomeSpecificError> {
        do_some_io()?;
        // ...
    }

Previously I would have written:

    fn do_something() -> Result<(), SomeSpecificError> {
        do_some_io().map_err(SomeSpecificError::Io)?;
    }

I find this approach results in clear code that continues to compile and work just fine over time, even as everything changes around it.

[0] https://jeltef.github.io/derive_more/derive_more/from.html#e...