Sum a tuple in swift 5.9?

i have a lot of stats counters that store the values inline in a homogenous tuple:

typealias Peers =

var count:Int 
    + self.followers.count  
    + self.requested.count  
    + self.blocked.count 

this is naturally quite error-prone, and i am interested in using parameter packs to simplify the count logic. but i couldn’t deduce how to actually iterate the Peers tuple in the absence of SE-0408, which is nightly-only.

is there a better way to reduce a tuple in swift 5.9?

This implementation will work!

func sumOfCountInTuple<each T: Collection>(_ target: (repeat each T)) -> Int { 
    var count = 0 
    func call(with peers: some Collection) {
        count += peers.count 
    repeat call(with: each target) 
    return count 
print(sumOfCountInTuple(([1,2,3], [4,5], [6,7]))) // 7

Sadly, currently, it is not possible to limit T.Element == Peer though. It produces error: same-element requirements are not yet supported error.


It also seems to be possible to repeat increment directly:

var sum = 0
repeat sum += (each t).count
return sum

What I can't get working is to call this function with a tuple with labels. It produces error: Cannot convert value of type '(a: [Int], b: [String])' to expected argument type '(repeat each T)' or just crashes.