Extensions to Apple's Combine framework to interoperate with Swift 5.5's new concurrency features

Combine+concurrency.swift

import Combine

extension Publisher {
    var stream: AsyncThrowingStream<Output> {
        AsyncThrowingStream(Output.self) { continuation in
            let cancellable = sink { completion in
                switch completion {
                case .finished: continuation.finish()
                case .failure(let error): continuation.finish(throwing: error)
                }
            } receiveValue: { output in
                continuation.yield(output)
            }
            
            continuation.onTermination = { _ in cancellable.cancel() }
        }
    }
}

extension Publisher where Failure == Never {
    var stream: AsyncStream<Output> {
        AsyncStream(Output.self) { continuation in
            let cancellable = sink { _ in
                continuation.finish()
            } receiveValue: { output in
                continuation.yield(output)
            }
            
            continuation.onTermination = { _ in cancellable.cancel() }
        }
    }
}

extension AsyncSequence {
    var first: Element? {
        get async throws {
            try await self.first { _ in true }
        }
    }
}

protocol AsyncPublisherSequence: Publisher, AsyncSequence {}

extension AsyncPublisherSequence where Element == Output {
    func makeAsyncIterator() -> AsyncThrowingStream<Output>.Iterator {
        stream.makeAsyncIterator()
    }
}

extension AsyncPublisherSequence where Element == Output, Failure == Never {
    func makeAsyncIterator() -> AsyncStream<Output>.Iterator {
        stream.makeAsyncIterator()
    }
}

extension Published.Publisher: AsyncPublisherSequence {}
extension AnyPublisher: AsyncPublisherSequence {}
extension Publishers.Sequence: AsyncPublisherSequence {}
extension Publishers.CombineLatest: AsyncPublisherSequence {}
extension Publishers.CombineLatest3: AsyncPublisherSequence {}
extension Publishers.CombineLatest4: AsyncPublisherSequence {}
extension Publishers.Merge: AsyncPublisherSequence {}
extension Publishers.Merge3: AsyncPublisherSequence {}
extension Publishers.Merge4: AsyncPublisherSequence {}
extension Publishers.Merge5: AsyncPublisherSequence {}
extension Publishers.Merge6: AsyncPublisherSequence {}
extension Publishers.Merge7: AsyncPublisherSequence {}
extension Publishers.Merge8: AsyncPublisherSequence {}
extension Publishers.MergeMany: AsyncPublisherSequence {}
extension Publishers.Zip: AsyncPublisherSequence {}
extension Publishers.Zip3: AsyncPublisherSequence {}
extension Publishers.Zip4: AsyncPublisherSequence {}