AsyncWrappedSequence.swift

struct AsyncWrappedSequence<Base: Sequence>: AsyncSequence {
    typealias Element = Base.Element

    struct AsyncIterator<BaseIterator>: AsyncIteratorProtocol where BaseIterator == Base.Iterator {
        var base: BaseIterator

        mutating func next() async -> BaseIterator.Element? {
            base.next()
        }
    }

    let base: Base

    func makeAsyncIterator() -> AsyncIterator<Base.Iterator> {
        .init(base: base.makeIterator())
    }
}

extension Sequence {
    var async: AsyncWrappedSequence<Self> { .init(base: self) }
}