Am 01.10.2026 um 02:29 schrieb Karoly Negyesi:
I submitted a draft RFC to https://github.com/php/php-src/pull/24030
<https://github.com/php/php-src/pull/24030>. The PR contains an
implementation and tests (please be gentle, I haven't written C in decades).
I propose an "implements by" syntax to automate delegation, closely
modelled on Kotlin.
In short,
interface T { function foo(); }
class A implements T { function foo() { print "A"; } }
class C implements T by $t { function __construct(private T $t) {} }
new C(new A)->foo();
The RFC motivates this feature with "unnecessary boilerplate and
maintenance burden as the interface gets more methods over time". I think
this premise is flawed: an interface that keeps gaining methods over time
usually violates the Interface Segregation Principle. The remedy for that
is smaller, more focused interfaces, not language support that makes
delegating to ever-growing interfaces cheaper.
There is also a correctness concern: with generated forwarding, a method
that is later added to the interface is silently delegated by every class
that uses "implements ... by". In the RFC's own example, a new
URL-generating method would be forwarded without the metadata bubbling
that MetadataBubblingUrlGenerator exists for. Today, such a change forces
the author of the decorator to make a conscious decision.
I am also not convinced that any benefit this may have outweighs its
downsides: it adds new syntax that static analysis tools need to learn
about, and it adds complexity to the compiler. The "To the Ecosystem"
section currently only lists "Less boilerplate"; it should account for
these costs as well.
--
Sebastian Bergmann https://phpunit.expert
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