On Sat, Aug 24, 2024, at 11:49 AM, 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
I am still not fully sold on this, but I like it a lot better than the previous attempt at a default
keyword. It's good that you mention named arguments, as those do replace like 95% of the use
cases for "put default here" in potential function calls, and the ones it doesn't,
you call out explicitly as the justification for this RFC.
The approach here seems reasonable overall. The mental model I have from the RFC is "yoink the
default value out of the function, drop it into this expression embedded in the function call, and
let the chips fall where they may." Is that about accurate?
My main holdup is the need. I... can't recall ever having a situation where this is something
I needed. Some of the examples show valid use cases (eg, the "default plus this binary
flag" example), but again, I've never actually run into that myself in practice.
My other concern is the list of supported expression types. I understand how the implementation
would naturally make all of those syntactically valid, but it seems many of them, if not most, are
semantically nonsensical. Eg, default > 1 would take a presumably numeric default
value and output a boolean, which should really never be type compatible with the function being
called. (A param type of int|bool is a code smell at best, and a fatal waiting to happen at worst.)
In practice, I think a majority of those expressions would be logically nonsensical, so I wonder if
it would be better to only allow a few reasonable ones and block the others, to keep people from
thinking nonsensical code would do something useful.
--Larry Garfield