The error maybe, but not the result of the call. The multiple-value return x, err is not a first-class value. It cannot be handled like any other variable.

This was demonstrated very clearly with proposal for try. try would have automatically returned with err when err != nil. But what if you wanted to change the error, say create an error message? Then try was completely useless. In Rust, where the result actually is just a regular value, you can transform the error however you like just like any other value and try is just as useful as before.