Guard out awaitUsingExpectation for SWIFT_CONCURRENCY_WAITER mode

Also this revealed teardown blocks were not being run in the mode, so
fix that as well.

Author: kateinoigakukun

Sources/XCTest/Private/XCTestCase.TearDownBlocksState.swift

@@ -12,18 +12,31 @@ extension XCTestCase {
     /// Supports async and sync throwing methods.
     final class TeardownBlocksState {
 
+        #if USE_SWIFT_CONCURRENCY_WAITER
+        typealias TeardownBlock = @Sendable () async throws -> Void
+        #else
+        typealias TeardownBlock = () throws -> Void
+        #endif
+
         private var wasFinalized = false
-        private var blocks: [() throws -> Void] = []
+        private var blocks: [TeardownBlock] = []
 
         // We don't want to overload append(_:) below because of how Swift will implicitly promote sync closures to async closures,
         // which can unexpectedly change their semantics in difficult to track down ways.
         //
         // Because of this, we chose the unusual decision to forgo overloading (which is a super sweet language feature <3) to prevent this issue from surprising any contributors to corelibs-xctest
         @available(macOS 12.0, *)
         func appendAsync(_ block: @Sendable @escaping () async throws -> Void) {
+            #if USE_SWIFT_CONCURRENCY_WAITER
+            XCTWaiter.subsystemQueue.sync {
+                precondition(wasFinalized == false, "API violation -- attempting to add a teardown block after teardown blocks have been dequeued")
+                blocks.append(block)
+            }
+            #else
             self.append {
                 try awaitUsingExpectation { try await block() }
             }
+            #endif
         }
 
         func append(_ block: @escaping () throws -> Void) {
@@ -33,7 +46,7 @@ extension XCTestCase {
             }
         }
 
-        func finalize() -> [() throws -> Void] {
+        func finalize() -> [TeardownBlock] {
             XCTWaiter.subsystemQueue.sync {
                 precondition(wasFinalized == false, "API violation -- attempting to run teardown blocks after they've already run")
                 wasFinalized = true

Sources/XCTest/Public/XCTestCase.swift

@@ -300,21 +300,8 @@ open class XCTestCase: XCTest {
         }
     }
 
-    private func runTeardownBlocks() {
-        for block in self.teardownBlocksState.finalize().reversed() {
-            do {
-                try block()
-            } catch {
-                handleErrorDuringTearDown(error)
-            }
-        }
-    }
-
-    private func performPreTearDown() {
-        runTeardownBlocks()
-
-        func syncTearDown() { tearDown() }
-        syncTearDown()
+    private func performSyncTearDown() {
+        tearDown()
 
         do {
             try tearDownWithError()
@@ -324,6 +311,16 @@ open class XCTestCase: XCTest {
     }
 
     #if USE_SWIFT_CONCURRENCY_WAITER
+    private func runTeardownBlocks() async {
+        for block in self.teardownBlocksState.finalize().reversed() {
+            do {
+                try await block()
+            } catch {
+                handleErrorDuringTearDown(error)
+            }
+        }
+    }
+
     private func performSetUpSequence() async {
         do {
             if #available(macOS 12.0, *) {
@@ -337,7 +334,8 @@ open class XCTestCase: XCTest {
     }
 
     private func performTearDownSequence() async {
-        performPreTearDown()
+        await runTeardownBlocks()
+        performSyncTearDown()
 
         do {
             try await self.tearDown()
@@ -346,6 +344,16 @@ open class XCTestCase: XCTest {
         }
     }
     #else
+    private func runTeardownBlocks() {
+        for block in self.teardownBlocksState.finalize().reversed() {
+            do {
+                try block()
+            } catch {
+                handleErrorDuringTearDown(error)
+            }
+        }
+    }
+
     private func performSetUpSequence() {
         do {
             if #available(macOS 12.0, *) {
@@ -360,7 +368,8 @@ open class XCTestCase: XCTest {
     }
 
     private func performTearDownSequence() {
-        performPreTearDown()
+        runTeardownBlocks()
+        performSyncTearDown()
 
         do {
             if #available(macOS 12.0, *) {
@@ -436,11 +445,11 @@ public func asyncTest<T: XCTestCase>(
 #endif
 }
 
+#if !USE_SWIFT_CONCURRENCY_WAITER
 @available(macOS 12.0, *)
 func awaitUsingExpectation(
     _ closure: @escaping () async throws -> Void
 ) throws -> Void {
-#if !USE_SWIFT_CONCURRENCY_WAITER
     let expectation = XCTestExpectation(description: "async test completion")
     let thrownErrorWrapper = ThrownErrorWrapper()
 
@@ -459,8 +468,8 @@ func awaitUsingExpectation(
     if let error = thrownErrorWrapper.error {
         throw error
     }
-#endif
 }
+#endif
 
 private final class ThrownErrorWrapper: @unchecked Sendable {