[Concurrency] Add an API for extracting the isolation of a dynamically isolated

function value.

Author: hborla

include/swift/Basic/Features.def

@@ -290,7 +290,7 @@ EXPERIMENTAL_FEATURE(DynamicActorIsolation, false)
 EXPERIMENTAL_FEATURE(BorrowingSwitch, true)
 
 // Enable isolated(any) attribute on function types.
-EXPERIMENTAL_FEATURE(IsolatedAny, false)
+EXPERIMENTAL_FEATURE(IsolatedAny, true)
 
 #undef EXPERIMENTAL_FEATURE_EXCLUDED_FROM_MODULE_INTERFACE
 #undef EXPERIMENTAL_FEATURE

stdlib/public/Concurrency/Actor.swift

@@ -85,3 +85,11 @@ internal func _enqueueOnMain(_ job: UnownedJob)
 public macro isolation<T>() -> T = Builtin.IsolationMacro
 #endif
 
+#if $IsolatedAny
+@available(SwiftStdlib 5.1, *)
+public func extractIsolation<each Arg, Result>(
+  _ fn: @escaping @isolated(any) (repeat each Arg) async throws -> Result
+) -> (any Actor)? {
+  return Builtin.extractFunctionIsolation(fn)
+}
+#endif

stdlib/public/Concurrency/CMakeLists.txt

@@ -60,6 +60,10 @@ else()
   list(APPEND SWIFT_RUNTIME_CONCURRENCY_C_FLAGS "-fswift-async-fp=never")
 endif()
 
+list(APPEND SWIFT_RUNTIME_CONCURRENCY_SWIFT_FLAGS
+  "-enable-experimental-feature"
+  "IsolatedAny"
+)
 
 list(APPEND SWIFT_RUNTIME_CONCURRENCY_C_FLAGS
   "-D__STDC_WANT_LIB_EXT1__=1")

test/Concurrency/isolated_any.swift

@@ -7,6 +7,9 @@ func globalNonisolatedFunction() {}
 
 actor A {
   func actorFunction() {}
+  func asyncActorFunction() async {}
+  func asyncThrowsActorFunction() async throws {}
+  func actorFunctionWithArgs(value: Int) async -> String { "" }
 }
 
 func testBasic_sync() {
@@ -71,3 +74,12 @@ func testConvertIsolatedAnyToMainActor(fn: @Sendable @isolated(any) () -> ()) {
   // expected-error @+1 {{cannot convert value of type '@isolated(any) @Sendable () -> ()' to expected argument type '@MainActor @Sendable () -> ()'}}
   requireSendableGlobalActor(fn)
 }
+
+func extractFunctionIsolation(_ fn: @isolated(any) @escaping () async -> Void) {
+  let _: (any Actor)? = extractIsolation(fn)
+
+  let myActor = A()
+  let _: (any Actor)? = extractIsolation(myActor.asyncActorFunction)
+  let _: (any Actor)? = extractIsolation(myActor.asyncThrowsActorFunction)
+  let _: (any Actor)? = extractIsolation(myActor.actorFunctionWithArgs(value:))
+}