Re: [PHP-DEV] [Discussion] Revisiting typed closures

On Sat, 4 Jul 2026 at 12:01, Matheus Martins <[email protected]> wrote:
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> Totally with you on not special-casing closures. A general alias feature is the right long-term home. But I'd push back on waiting for it before settling the inline syntax, because the two aren't really alternatives.
>
> I'm no expert in the topic, but I guess an alias needs something to alias. use type callable(int): string as Foo; probably only works once callable(int): string is a valid type on its own or something like that. I mean supporting the inline syntax doesn't sound like conflicting / additional work that type alias could avoid.
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> If that's correct, the inline grammar is the primitive; aliases are just a naming layer on top, and we would need inline either way.
>
> I just found that C# is a nice warning signal here: it started reference-only (you had to declare a named delegate per signature), found that painful enough that Func/Action were added precisely so you don't have to declare a delegate to spell a function type.
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> See https://learn.microsoft.com/en-us/dotnet/api/system.func-2?view=net-10.0
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> Even the reference-only poster child ended up needing a declaration-free way to write these inline.
>
> Last but not least, the type-aliases RFC is still under discussion, with callable signatures sitting in future scope.
>
> Does it makes sense to wait for something that isn't a blocker nor an enabler?

To clarify, I did not mean we should have no closure types until type
aliases land. My point was specifically that we should not add
dedicated "closure references" (like the C# delegates mentioned)
before type aliases, as a general type alias feature would eventually
make such specialized references redundant.

I fully agree that we should have inline function types now, while
leaving type aliases for later to solve the problems of repetition and
signature complexity.