Initial, composed implementation of `Publisher.withLatestFrom`’s handling of finished events.

with_latest_from_finished_events.swift

// …back to using our implementation —

// **Scenario one**: `withLatestFrom`’s argument finishes first.

let first = PassthroughSubject<Int, Never>()
let second = PassthroughSubject<String, Never>()
var cancellables = Set<AnyCancellable>()

first
	.withLatestFrom(second)
	.sink(receiveCompletion: { print($0) }, receiveValue: { print($0) })
	.store(in: &cancellables)

first.send(1)
second.send("one")
first.send(2)
second.send("two")
second.send(completion: .finished)

// Outputs:
//
// ```
// one
// ```

// **Scenario two**: Upstream finishes first.

// …

first.send(1)
second.send("one")
first.send(2)
second.send("two")
first.send(completion: .finished)

// Outputs:
//
// ```
// one
// ```