On Fri, Mar 22, 2024 at 8:02 PM Rowan Tommins [IMSoP] <imsop....@rwec.co.uk> wrote: > > On Fri, 22 Mar 2024, at 17:38, Claude Pache wrote: > > > Le 22 mars 2024 à 16:18, Rowan Tommins [IMSoP] <imsop....@rwec.co.uk> a écrit > : > > $optionalExpiryDateTime = $expiry as ?DateTimeInterface else > some_other_function($expiry); > assert($optionalExpiryDateTime is ?DateTimeInterface); // cannot fail, > already asserted by the "as" > > > I think that the `is` operator is all we need; the `as` operator adds syntax > complexity for little gain. Compare: > > $optionalExpiryDateTime = $expiry as ?DateTimeInterface else > some_other_function($expiry); > > vs > > $optionalExpiryDateTime = $expiry is ?DateTimeInterface ? $expiry : > some_other_function($expiry); > > > > I agree, it doesn't add much; and that's what the draft RFC Ilija linked to > says as well. > > But the point of that particular example is that after the "is" version, you > don't actually know the type of $optionalExpiryDateTime without looking up > the return type of some_other_function() > > With the "as" version, you can see at a glance that after that line, > $optionalExpiryDateTime is *guaranteed* to be DateTimeInterface or null, > which I understood to be the intention of Robert's original proposal on this > thread. > > -- > Rowan Tommins > [IMSoP] >
Indeed, "as" is to pattern matching like the fn is to function. You can live with one or the other, but having both is much more useful.
