Merge pull request swiftlang#68451 from ktoso/wip-radar-91857262

[Distributed] Add test coverage for extension where Self: DistributedActor

Author: swift-ci

test/Distributed/distributed_protocol_allow_extension_where_self_distributedactr.swift

@@ -0,0 +1,16 @@
+// RUN: %target-typecheck-verify-swift -disable-availability-checking
+// REQUIRES: concurrency
+// REQUIRES: distributed
+
+import Distributed
+
+/// This adds test coverage for rdar://91857262 in which the extension below would cause a crash.
+protocol GamePlayer: Sendable, Identifiable where ID == LocalTestingDistributedActorSystem.ActorID {}
+
+extension GamePlayer where Self: DistributedActor, ActorSystem == LocalTestingDistributedActorSystem {
+  distributed func startGame(with opponent: String) -> String { opponent }
+}
+
+distributed actor FishPlayer: GamePlayer {
+  typealias ActorSystem = LocalTestingDistributedActorSystem
+}