Re: [Discussion] Revisiting typed closures

On 1 July 2026 20:02:27 BST, Seifeddine Gmati <azjezz@carthage.software> wrote: >Making Closure generic (e.g., say >Closure<Input, Output> ) would >require Input to be variadic to stand in for a closure's >parameter >list, and variadic generics are a different beast entirely. FWIW, C# has a long list of overloads for expressing generic lambda types, like Action<T1,T2>, Action<T1,T2,T3>, Func<T1,T2,TResult> and so on and on and on <https://github.com/dotnet/dotnet/blob/b0f34d51fccc69fd334253924abd8d6853fad7aa/src/runtime/src/libraries/System.Private.CoreLib/src/System/Action.cs> <https://github.com/dotnet/dotnet/blob/b0f34d51fccc69fd334253924abd8d6853fad7aa/src/runtime/src/libraries/System.Private.CoreLib/src/System/Function.cs> Ugly, and unlikely to even work in a PHP implementation of generics. On the other hand, it has an elegant "delegate" syntax for what are effectively named callable types: https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/delegates/ That *would* translate well to PHP. Translating one of their examples: delegate ProcessBookCallback(Book $book): void; public function processPaperbackBooks(ProcessBookCallback $processBook): void { foreach ($this->list as $b) { if ($b->paperback) { $processBook($b); } } } Just an additional angle to throw into the mix. Rowan Tommins [IMSoP]