workaround 5.10

Author: glbrntt

Tests/AsyncHTTPClientTests/TransactionTests.swift

@@ -657,6 +657,7 @@ private actor Promise<Value: Sendable> {
 
 @available(macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, *)
 extension Transaction {
+    #if compiler(>=6.0)
     fileprivate static func makeWithResultTask(
         request: sending PreparedRequest,
         requestOptions: RequestOptions = .forTests(),
@@ -684,4 +685,40 @@ extension Transaction {
 
         return (await transactionPromise.value, task)
     }
+    #else
+    fileprivate static func makeWithResultTask(
+        request: PreparedRequest,
+        requestOptions: RequestOptions = .forTests(),
+        logger: Logger = Logger(label: "test"),
+        connectionDeadline: NIODeadline = .distantFuture,
+        preferredEventLoop: EventLoop
+    ) async -> (Transaction, _Concurrency.Task<HTTPClientResponse, Error>) {
+        // It isn't sendable ... but on 6.0 and later we use 'sending'.
+        struct UnsafePrepareRequest: @unchecked Sendable {
+            var value: PreparedRequest
+        }
+
+        let transactionPromise = Promise<Transaction>()
+        let unsafe = UnsafePrepareRequest(value: request)
+        let task = Task {
+            try await withCheckedThrowingContinuation {
+                (continuation: CheckedContinuation<HTTPClientResponse, Error>) in
+                let request = unsafe.value
+                let transaction = Transaction(
+                    request: request,
+                    requestOptions: requestOptions,
+                    logger: logger,
+                    connectionDeadline: connectionDeadline,
+                    preferredEventLoop: preferredEventLoop,
+                    responseContinuation: continuation
+                )
+                Task {
+                    await transactionPromise.fulfil(transaction)
+                }
+            }
+        }
+
+        return (await transactionPromise.value, task)
+    }
+    #endif
 }