On Tuesday 19 May 2026 11:45:14 (+02:00), Ondřej Mirtes wrote:
> On 6. 5. 2026 at 22:09:45, Bob Weinand <[email protected]> wrote:
>
> > Volker and I drafted a RFC:
> >
>
> Hello, I’d like to offer my 2c as PHPStan maintainer. References are really
> hard to wrap our head around. [...]
I only just saw this discussion – the combinatorial
explosion Ondřej describes with references and closures
is something I’ve been brushing against while working on
the *scanf() counter fix for PHPStan.
One thought that’s been growing out of that work and the
original %c report php-src GH-19088: what if PHP could
declare the return arity of a function directly?
Something like:
.listing
function fn(): [int, Error|null] { … } // binary return
function fn(): [] { … } // nulary return
function fn(): [int...] { … } // variadic int return (zero or more)
function fn(): [int, ...] { … } // variadic int return (one or more)
The dot-dot-dot '...' borrows the left‑hand type if none
is given (or means mixed if no left type). A call would
destructure naturally:
.listing
[$a, $b, $c] = fn();
// or with null‑filling:
[$a, $b, $c] = fn() + [null, null, null];
This would give the static analyser a fixed skeleton to
hang its inferences on, even when the actual return is
variadic.
The combinatorial explosion of tracking references
through closures would still exist, but the return site
itself would be a clear contract.
The analyser wouldn’t need to guess the shape of the
returned array; it would be declared right there, much
like the counter in PHPStan asks the runtime for the
exact count of placeholders.
This isn’t an RFC – I’m not fond of writing those. It’s
just a paper‑trail: a small idea that emerged from
fixing a decades‑old sscanf bug,
and that might be useful to someone thinking about
return types in the future.
The counter already measures return arity today; a
native syntax would just make that measurement explicit.
I find this ordinarily simplistic and therefore wonder
if there isn't prior art, specifically in PHP for this.
Feel free to send me any references off‑list or ping me
in room 11.
-- hakre
