flatMap on Shared?

[kamcma]

I wonder if anyone has explored or would find useful a flatMap on Shared? I find myself wanting functionality similar to flatMap on Publisher in Combine, where the transform closure produces a new Shared (actually SharedReader, probably) rather than a new Value.

A little pseudocode to illustrate the functionality, borrowing the FactKey from the APIClientDemo:

@Test func sharedFlatMap() async throws {
  @Shared(.inMemory("count")) var count = 3

  @SharedReader var fact = $count.flatMap { count in
    return FactKey(number: count)
  }

  try await $fact.load()
  #expect(fact == "3 is a very good number.")

  $count.withLock { $0 += 1 }

  try await $fact.load()
  #expect(fact == "4 is a very good number.")
}

I don't know if this is exactly the right shape. I have my theoretical implementation of flatMap returning a SharedReaderKey rather than a SharedReader per se so the implementation can call SharedReader.load(_:) async throws rather than re-creating the whole reader. I presume this might require a new Reference implementation, eg _FlatMapClosureReference: Reference { ... }?

Thoughts? If this is fundamentally not possible for XYZ reason, or there's already a way to achieve similar functionality with existing APIs, those responses are welcome too.