Update compiler guards for concurrency (#1277)

Motivation:

The 'right' way to check if Swift concurrency is available is to use
`#if compiler(>=5.5) && canImport(_Concurrency)`. We are missing
currently missing the `canImport` check.

Modifications:

Add check for `canImport(_Concurrency)`.

Results:

We more correctly check whether concurrency is available.

Sources/Examples/Echo/Implementation/EchoAsyncProvider.swift

@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-#if compiler(>=5.5)
+#if compiler(>=5.5) && canImport(_Concurrency)
 import EchoModel
 import GRPC
 
@@ -69,4 +69,4 @@ public final class EchoAsyncProvider: Echo_EchoAsyncProvider {
   }
 }
 
-#endif // compiler(>=5.5)
+#endif // compiler(>=5.5) && canImport(_Concurrency)

Sources/Examples/Echo/Model/echo.grpc.swift

@@ -172,7 +172,7 @@ public final class Echo_EchoClient: Echo_EchoClientProtocol {
   }
 }
 
-#if compiler(>=5.5)
+#if compiler(>=5.5) && canImport(_Concurrency)
 @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
 public protocol Echo_EchoAsyncClientProtocol: GRPCClient {
   var serviceName: String { get }
@@ -334,7 +334,7 @@ public struct Echo_EchoAsyncClient: Echo_EchoAsyncClientProtocol {
   }
 }
 
-#endif // compiler(>=5.5)
+#endif // compiler(>=5.5) && canImport(_Concurrency)
 
 public final class Echo_EchoTestClient: Echo_EchoClientProtocol {
   private let fakeChannel: FakeChannel
@@ -542,7 +542,7 @@ public protocol Echo_EchoServerInterceptorFactoryProtocol {
   func makeUpdateInterceptors() -> [ServerInterceptor<Echo_EchoRequest, Echo_EchoResponse>]
 }
 
-#if compiler(>=5.5)
+#if compiler(>=5.5) && canImport(_Concurrency)
 
 /// To implement a server, implement an object which conforms to this protocol.
 @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
@@ -633,5 +633,5 @@ extension Echo_EchoAsyncProvider {
   }
 }
 
-#endif // compiler(>=5.5)
+#endif // compiler(>=5.5) && canImport(_Concurrency)
 

Sources/GRPC/AsyncAwaitSupport/AsyncWriter.swift

@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-#if compiler(>=5.5)
+#if compiler(>=5.5) && canImport(_Concurrency)
 import NIOCore
 
 /// An asynchronous writer which forwards messages to a delegate.
@@ -334,4 +334,4 @@ internal protocol AsyncWriterDelegate: AnyObject {
   func writeEnd(_ end: End)
 }
 
-#endif // compiler(>=5.5)
+#endif // compiler(>=5.5) && canImport(_Concurrency)

Sources/GRPC/AsyncAwaitSupport/Call+AsyncRequestStreamWriter.swift

@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-#if compiler(>=5.5)
+#if compiler(>=5.5) && canImport(_Concurrency)
 
 @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
 extension Call {
@@ -30,4 +30,4 @@ extension Call {
   }
 }
 
-#endif // compiler(>=5.5)
+#endif // compiler(>=5.5) && canImport(_Concurrency)

Sources/GRPC/AsyncAwaitSupport/CancellationError+GRPCStatusTransformable.swift

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-#if compiler(>=5.5)
+#if compiler(>=5.5) && canImport(_Concurrency)
 
 @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
 extension CancellationError: GRPCStatusTransformable {

Sources/GRPC/AsyncAwaitSupport/GRPCAsyncBidirectionalStreamingCall.swift

@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-#if compiler(>=5.5)
+#if compiler(>=5.5) && canImport(_Concurrency)
 
 import NIOHPACK
 

Sources/GRPC/AsyncAwaitSupport/GRPCAsyncClientStreamingCall.swift

@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-#if compiler(>=5.5)
+#if compiler(>=5.5) && canImport(_Concurrency)
 
 import NIOHPACK
 

Sources/GRPC/AsyncAwaitSupport/GRPCAsyncRequestStream.swift

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-#if compiler(>=5.5)
+#if compiler(>=5.5) && canImport(_Concurrency)
 
 /// This is currently a wrapper around AsyncThrowingStream because we want to be
 /// able to swap out the implementation for something else in the future.

Sources/GRPC/AsyncAwaitSupport/GRPCAsyncRequestStreamWriter.swift

@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-#if compiler(>=5.5)
+#if compiler(>=5.5) && canImport(_Concurrency)
 
 /// An object allowing the holder -- a client -- to send requests on an RPC.
 ///
@@ -124,4 +124,4 @@ extension GRPCAsyncRequestStreamWriter {
   }
 }
 
-#endif // compiler(>=5.5)
+#endif // compiler(>=5.5) && canImport(_Concurrency)

Sources/GRPC/AsyncAwaitSupport/GRPCAsyncResponseStream.swift

@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-#if compiler(>=5.5)
+#if compiler(>=5.5) && canImport(_Concurrency)
 
 /// This is currently a wrapper around AsyncThrowingStream because we want to be
 /// able to swap out the implementation for something else in the future.

Sources/GRPC/AsyncAwaitSupport/GRPCAsyncResponseStreamWriter.swift

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-#if compiler(>=5.5)
+#if compiler(>=5.5) && canImport(_Concurrency)
 
 /// Writer for server-streaming RPC handlers to provide responses.
 @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)

Sources/GRPC/AsyncAwaitSupport/GRPCAsyncServerCallContext.swift

@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-#if compiler(>=5.5)
+#if compiler(>=5.5) && canImport(_Concurrency)
 
 import Logging
 import NIOConcurrencyHelpers

Sources/GRPC/AsyncAwaitSupport/GRPCAsyncServerHandler.swift

@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-#if compiler(>=5.5)
+#if compiler(>=5.5) && canImport(_Concurrency)
 
 import _NIOConcurrency
 import NIOCore

Sources/GRPC/AsyncAwaitSupport/GRPCAsyncServerStreamingCall.swift

@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-#if compiler(>=5.5)
+#if compiler(>=5.5) && canImport(_Concurrency)
 
 import NIOHPACK
 

Sources/GRPC/AsyncAwaitSupport/GRPCAsyncUnaryCall.swift

@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-#if compiler(>=5.5)
+#if compiler(>=5.5) && canImport(_Concurrency)
 
 import NIOHPACK
 

Sources/GRPC/AsyncAwaitSupport/GRPCChannel+AsyncAwaitSupport.swift

@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-#if compiler(>=5.5)
+#if compiler(>=5.5) && canImport(_Concurrency)
 
 import SwiftProtobuf
 

Sources/GRPC/AsyncAwaitSupport/GRPCClient+AsyncAwaitSupport.swift

@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-#if compiler(>=5.5)
+#if compiler(>=5.5) && canImport(_Concurrency)
 
 import SwiftProtobuf
 

Sources/GRPC/AsyncAwaitSupport/PassthroughMessageSequence.swift

@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-#if compiler(>=5.5)
+#if compiler(>=5.5) && canImport(_Concurrency)
 
 /// An ``AsyncSequence`` adapter for a ``PassthroughMessageSource``.`
 @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
@@ -55,4 +55,4 @@ internal struct PassthroughMessageSequence<Element, Failure: Error>: AsyncSequen
   }
 }
 
-#endif // compiler(>=5.5)
+#endif // compiler(>=5.5) && canImport(_Concurrency)

Sources/GRPC/AsyncAwaitSupport/PassthroughMessageSource.swift

@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-#if compiler(>=5.5)
+#if compiler(>=5.5) && canImport(_Concurrency)
 import NIOConcurrencyHelpers
 import NIOCore
 
@@ -160,4 +160,4 @@ internal final class PassthroughMessageSource<Element, Failure: Error> {
   }
 }
 
-#endif // compiler(>=5.5)
+#endif // compiler(>=5.5) && canImport(_Concurrency)

Sources/protoc-gen-grpc-swift/Generator.swift

@@ -170,10 +170,10 @@ class Generator {
   }
 
   func printIfCompilerGuardForAsyncAwait() {
-    self.println("#if compiler(>=5.5)")
+    self.println("#if compiler(>=5.5) && canImport(_Concurrency)")
   }
 
   func printEndCompilerGuardForAsyncAwait() {
-    self.println("#endif // compiler(>=5.5)")
+    self.println("#endif // compiler(>=5.5) && canImport(_Concurrency)")
   }
 }