Deprecate type-erasing AsyncStream.init (#41)

In Swift 6, we can erase `any AsyncSequence<Element, Failure>` directly.

Author: stephencelis

README.md

@@ -54,35 +54,6 @@ sendability of the underlying value.
 
 The library comes with numerous helper APIs spread across the two Swift stream types:
 
-  * There are helpers that erase any `AsyncSequence` conformance to either concrete stream type.
-    This allows you to treat the stream type as a kind of "type erased" `AsyncSequence`.
-
-    For example, suppose you have a dependency client like this:
-
-    ```swift
-    struct ScreenshotsClient {
-      var screenshots: () -> AsyncStream<Void>
-    }
-    ```
-
-    Then you can construct a live implementation that "erases" the
-    `NotificationCenter.Notifications` async sequence to a stream:
-
-    ```swift
-    extension ScreenshotsClient {
-      static let live = Self(
-        screenshots: {
-          NotificationCenter.default
-            .notifications(named: UIApplication.userDidTakeScreenshotNotification)
-            .map { _ in }
-            .eraseToStream()  // ⬅️
-        }
-      )
-    }
-    ```
-
-    Use `eraseToThrowingStream()` to propagate failures from throwing async sequences.
-
   * Swift 5.9's `makeStream(of:)` functions have been back-ported. It can be handy in tests that need
     to override a dependency endpoint that returns a stream:
 

Sources/ConcurrencyExtras/AsyncStream.swift

@@ -52,6 +52,12 @@ extension AsyncStream {
   /// ```
   ///
   /// - Parameter sequence: An async sequence.
+  @available(iOS, deprecated: 18, message: "Use 'any AsyncSequence<Element, Never>', instead.")
+  @available(macOS, deprecated: 15, message: "Use 'any AsyncSequence<Element, Never>', instead.")
+  @available(tvOS, deprecated: 18, message: "Use 'any AsyncSequence<Element, Never>', instead.")
+  @available(
+    watchOS, deprecated: 11, message: "Use 'any AsyncSequence<Element, Never>', instead."
+  )
   public init<S: AsyncSequence>(_ sequence: S) where S.Element == Element, S: Sendable {
     let lock = NSLock()
     let iterator = UncheckedBox<S.AsyncIterator?>(wrappedValue: nil)
@@ -79,6 +85,12 @@ extension AsyncStream {
 extension AsyncSequence {
   /// Erases this async sequence to an async stream that produces elements till this sequence
   /// terminates (or fails).
+  @available(iOS, deprecated: 18, message: "Use 'any AsyncSequence<Element, Never>', instead.")
+  @available(macOS, deprecated: 15, message: "Use 'any AsyncSequence<Element, Never>', instead.")
+  @available(tvOS, deprecated: 18, message: "Use 'any AsyncSequence<Element, Never>', instead.")
+  @available(
+    watchOS, deprecated: 11, message: "Use 'any AsyncSequence<Element, Never>', instead."
+  )
   public func eraseToStream() -> AsyncStream<Element> where Self: Sendable {
     AsyncStream(self)
   }

Sources/ConcurrencyExtras/AsyncThrowingStream.swift

@@ -5,6 +5,14 @@ extension AsyncThrowingStream where Failure == Error {
   /// terminates, rethrowing any failure.
   ///
   /// - Parameter sequence: An async sequence.
+  @available(iOS, deprecated: 18, message: "Use 'any AsyncSequence<Element, any Error>', instead.")
+  @available(
+    macOS, deprecated: 15, message: "Use 'any AsyncSequence<Element, any Error>', instead."
+  )
+  @available(tvOS, deprecated: 18, message: "Use 'any AsyncSequence<Element, any Error>', instead.")
+  @available(
+    watchOS, deprecated: 11, message: "Use 'any AsyncSequence<Element, any Error>', instead."
+  )
   public init<S: AsyncSequence>(_ sequence: S) where S.Element == Element, S: Sendable {
     let lock = NSLock()
     let iterator = UncheckedBox<S.AsyncIterator?>(wrappedValue: nil)
@@ -34,6 +42,14 @@ extension AsyncThrowingStream where Failure == Error {
 extension AsyncSequence {
   /// Erases this async sequence to an async throwing stream that produces elements till this
   /// sequence terminates, rethrowing any error on failure.
+  @available(iOS, deprecated: 18, message: "Use 'any AsyncSequence<Element, any Error>', instead.")
+  @available(
+    macOS, deprecated: 15, message: "Use 'any AsyncSequence<Element, any Error>', instead."
+  )
+  @available(tvOS, deprecated: 18, message: "Use 'any AsyncSequence<Element, any Error>', instead.")
+  @available(
+    watchOS, deprecated: 11, message: "Use 'any AsyncSequence<Element, any Error>', instead."
+  )
   public func eraseToThrowingStream() -> AsyncThrowingStream<Element, Error> where Self: Sendable {
     AsyncThrowingStream(self)
   }