Re: [RFC] Default expression

On 25/08/2024 10:49, Juliette Reinders Folmer wrote:

(resending as I accidentally originally send a private reply instead of sending the below to the list) On 24-8-2024 18:49, Bilge wrote:

Hi gang, New RFC just dropped: https://wiki.php.net/rfc/default_expression. I think some of you might enjoy this one. Hit me with any feedback. This one already comes complete with working implementation that I've been cooking for a little while. Considering I don't know C or PHP internals, one might think implementing this feature would be prohibitively difficult, but considering the amount of help and guidance I received from Ilija, Bob and others, it would be truer to say it would have been more difficult to fail! Huge thanks to them. Cheers, Bilge

Hi Bilge, Hi :)

I like the idea, but see some potential for issues with ambiguity, which I don't see mentioned in the RFC as "solved". Example 1:

function foo($paramA, $default = false) {}
foo( default: default ); // <= Will this be handled correctly ?

No, but not because of my RFC, but because $paramA is a required parameter that was not specified. Assuming that was just a typo, the following works as expected: function foo($paramA = 1, $default = false) {

    var_dump($default);

} foo(default: default); // bool(false)

Example 2:

callme(
    match($a) {
        10 => $a * 10,
        20 => $a * 20,
        default => $a * default, // <= Based on a test in the PR this should work. Could you confirm ?
    }
);

Yes.

Example 3:

switch($a) {
    case 'foo':
        return callMe($a, default); // I presume this shouldn't be a problem, but might still be good to have a test for this ?
    default:
        return callMe(10, default); // I presume this shouldn't be a problem, but might still be good to have a test for this ?
}

Yes.

On that note, might it be an idea to introduce a separate token for the default keyword when used as a default expression in a function call to reduce ambiguity ? Considering the Bison grammar compiles, I believe there can be no ambiguity. I specifically picked default because I think it is the most intuitive keyword to use for this, and it's conveniently already a reserved word.

Cheers, Bilge