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Date: Sun, 10 May 2026 23:33:32 -0600
Message-ID: <CAFMT4NoSrRp3hg+6AiMCfQJBF00nDWkbXs_bny=wmEhjhFTHAg@mail.gmail.com>
Subject: Re: [PHP-DEV] [RFC] [Discussion] Bound-Erased Generic Types
To: Seifeddine Gmati <azjezz@carthage.software>
Cc: php internals <internals@lists.php.net>
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From: levim@php.net (Levi Morrison)

On Sun, May 10, 2026 at 1:05=E2=80=AFPM Seifeddine Gmati
<azjezz@carthage.software> wrote:
>
> Hello Internals,
>
> I'd like to start the discussion on a new RFC adding bound-erased
> generics types to PHP.
>
> Generic type parameters can be declared on classes, interfaces,
> traits, functions, methods, closures, and arrow functions, with
> bounds, defaults, and variance markers. Type parameters erase to their
> bound at runtime; the pre-erasure form is preserved for Reflection and
> consumed by static analyzers.
>
> - RFC: https://wiki.php.net/rfc/bound_erased_generic_types
> - Implementation: https://github.com/php/php-src/pull/21969
>
> Thanks,
> Seifeddine.

Seifeddine,

This is a very interesting RFC, thank you!

I have a technical request: can we lower the limit from 255 to a 7-bit
max? I've done tons of optimization work in the last 8-10 years of my
life, and having a spare bit on things for the future has often been
rewarded. And for me, I can't imagine a use-case for having 128-255
type arguments in practice. Do you have any evidence that a 7-bit
maximum would be insufficient for real-world code?

Thanks, Levi Morrison