Re: Typed callable properties

On 22/04/2020 16:01, Michał Brzuchalski wrote:

I agree, a callable brings as much information as a resource type - you know the type but are unable to use it without additional information.

While this is true, it's somewhat orthogonal to the question Benas raised in this thread - namely, how to handle values that are callable in one scope but not another. That is, is the following code valid (error-free) or not? delegate Reducer (?int $sum, int $item = 0): int; class X {

    private static function myPrivateMethod(?int $sum, int $item = 0): int {
         return 0;
    }
    public static function runReducer(Reducer $r) {
         return $r(0, 0);
    }

} echo X::bar(['X', 'myPrivateMethod']); The equivalent code with a type constraint of "callable" currently runs fine, even though passing the same value to a different function would fail due to scoping. Making the delegate-constrained version throw an error for any private or protected method would just trade one inconsistency for another. A more reasonable restriction, IMO, would be to say that delegates only match Closure instances (and possibly other objects with a public __invoke method), not the various string and array syntaxes that "callable" currently allows. The case above would then need to bind the private method into a closure that is callable everywhere, e.g. using Closure::fromCallable([self::class, 'myPrivateMethod']); The obvious downside is that Closure::fromCallable is both verbose and a potential performance hit. So it seems we're back again to wanting a new syntax to succinctly and optimally generate such a closure. For instance, in the discussion of ::func, one suggestion was "$closure={self::myPrivateMethod};" and more recently it was mentioned that a variant of partial application is to not actually bind anything, and write "$closure=self::myPrivateMethod(?, ?);" Regards, -- Rowan Tommins (né Collins) [IMSoP]