proposal: Go 2: Implicit zero-return-value

[leonklingele]

For example, having a func returning (int, error), it's quite cumbersome to always explicitly return a zero-valued integer in case of an error:

func demo() (int, error) {
    if !someCondition {
        return 0, errors.New("someCondition failed")
    }
    if !someCondition2 {
        return 0, errors.New("someCondition2 failed")
    }

    return 42, nil
}

Using named return values instead makes this a bit easier (but they seem overly complicated and error-prone):

func demo() (i int, err error) {
    if !someCondition {
        err = errors.New("someCondition failed")
        return
    }
    if !someCondition2 {
        err = errors.New("someCondition2 failed")
        return
    }

    return 42, nil
}

What would be more useful, beautiful, is using an underscore (_) to implicitly return the zero-value of a return parameter — a don't-care value:

func demo() (int, error) {
    if !someCondition {
        return _, errors.New("someCondition failed")
    }
    if !someCondition2 {
        return _, errors.New("someCondition2 failed")
    }

    return 42, nil
}

Has this been proposed before?

[josharian]

See #21182 (which I quite like, but which doesn't seem to be very popular).

[seankhliao]

dup of #19642 ?

[DeedleFake]

@seankhliao

I don't think that it's an exact duplicate. That was allowing it in any RHS usage, while this seems to be only in returns.

[josharian]

In any case I think it’s fair to say that this proposal is reasonably well covered by existing issues. What do you think, @leonklingele ?

[seankhliao]

#21422 (exactly the same as this one) was closed as a dup of #19642

[leonklingele]

Closing as a dup of any of the aforementioned issues.