Getting an array of descriptions from a value pack in Swift 5.9 (WWDC 2023 beta)

variadicAccumulationFun.swift

// Given a value pack in Swift, one would like to be able to accumulate some uniformly-typed property into an array like so:

[repeat String(describing: each element)]

// However, this is not currently supported
// (error: value pack expansion can only appear inside a function argument list or tuple element)
//
// A workaround is to use the tuple conversion capability, with a side-effecting transformation:

var elementDescriptions: [String] = []
func accumulate(_ string: String) {
    elementDescriptions.append(string)
}
(repeat accumulate(String(describing: each element)))

// This fills out `elementDescriptions` while producing a tuple of Voids, which can be implicitly discarded.
//
// I don’t like it because it feels like having side effects in a `map`, even though the imperative `repeat` is right there.
// In any case, I believe this is the only workable approach right now.
//
// Also note that this can’t be abstracted out into a function, because it would require same-type constraints:

func accumulate<each T, R>(_ elements: repeat each T) -> [R] where repeat each T == R {}
// error: Same-element requirements are not yet supported