Even transforming an error is taken care of by ?

func()? desugars to (more or less)

    match func() {
        Ok(v) => v,
        Err(e) => return Err(e.into())
    }

I'm also not really sure what the complaint is. Go doesn't do any more implicit type conversion than Rust does. There are numerous solid arguments for Go over Rust, but error handling and automatic type punning aren't on the list.