Re: [RFC] Allow Reassignment of Promoted Readonly Properties in Constructor

On Tue, Feb 3, 2026, at 09:56, Nicolas Grekas wrote: > Hi Rob, > > Le mar. 3 févr. 2026 à 09:50, Rob Landers <rob@bottled.codes> a écrit : >> __ >> On Mon, Feb 2, 2026, at 22:14, Nicolas Grekas wrote: >>> Hi Marco, >>> >>> Le lun. 2 févr. 2026 à 11:54, Marco Pivetta <ocramius@gmail.com> a écrit : >>>> Hey Nicolas, >>>> >>>> >>>> On Thu, 22 Jan 2026 at 16:34, Nicolas Grekas <nicolas.grekas+php@gmail.com >>>> <mailto:nicolas.grekas%2Bphp@gmail.com>> wrote: >>>>> Dear all, >>>>> >>>>> Here is a new RFC for you to consider: >>>>> >>>>> https://wiki.php.net/rfc/promoted_readonly_constructor_reassign >>>> >>>> >>>> What happens if one calls $obj->__construct(1, 2, >>>> 3) (on an already instantiated $obj) in the context >>>> of this patch? >>> >>> Thanks for asking, I didn't think about this. This made me also think about >>> ReflectionClass::newInstanceWithoutConstructor(). >>> I clarified this in the RFC, see "Direct __construct() Calls Cannot Bypass >>> Readonly" and "Reflection: Objects Created Without Constructor". >>> Patch and PR updated also if anyone wants to run some code where this RFC can be played >>> with. >>> >>> Cheers, >>> Nicolas >> >> Hi Nicolas, >> >> Under "Child Classes Can Reassign Parent Properties": this feels like a major >> footgun. Calling parent::__construct() won't allow a reset (per the rules of calling a >> constructor directly); which would completely break inheritance... but then in the examples it says >> that calling a constructor directly can reset it -- but you can't? >> >> This feels really inconsistent to me. >> >> — Rob > > Yes, the text was ambiguous. The implementation allows parent::__construct() during the initial > construction (normal inheritance), and only blocks explicit __construct() calls after construction > completed. I’ve clarified this in the RFC. > > Nicolas Will this result in a catchable error? I assume so, so a valid pattern during inheritance might be to put these in a try/catch so children can set them first? FWIW, in my Records RFC, properties were fully mutable during construction for exactly this reason. — Rob