Remove #if compiler(>=5.5) (#2292)

### Motivation
We only support Swift 5.5.2+.

### Modification
Remove all `#if swift(>=5.5)` conditional compilation blocks.

### Result
less branching

CONTRIBUTING.md

@@ -72,7 +72,7 @@ For this reason, whenever you add new tests **you have to run a script** that ge
 
 ### Make sure your patch works for all supported versions of swift
 
-The CI will do this for you.  You can use the docker-compose files included if you wish to check locally.  Currently all versions of swift >= 5.5 are supported.  For example usage of docker compose see the main [README](./README.md#an-alternative-using-docker-compose)
+The CI will do this for you.  You can use the docker-compose files included if you wish to check locally.  Currently all versions of swift >= 5.5.2 are supported.  For example usage of docker compose see the main [README](./README.md#an-alternative-using-docker-compose)
 
 ### Make sure your code is performant
 

README.md

@@ -11,7 +11,7 @@ It's like [Netty](https://netty.io), but written for Swift.
 
 The SwiftNIO project is split across multiple repositories:
 
-Repository | NIO 2 (Swift 5.5+)
+Repository | NIO 2 (Swift 5.5.2+)
 --- | ---
 [https://github.com/apple/swift-nio][repo-nio] <br> SwiftNIO core | `from: "2.0.0"`
 [https://github.com/apple/swift-nio-ssl][repo-nio-ssl] <br> TLS (SSL) support | `from: "2.0.0"`
@@ -70,14 +70,14 @@ Redis | ✅ | ❌ | [mordil/swift-redi-stack](https://gitlab.com/Mordil/swift-re
 
 This is the current version of SwiftNIO and will be supported for the foreseeable future.
 
-The most recent versions of SwiftNIO support Swift 5.5 and newer. The minimum Swift version supported by SwiftNIO releases are detailed below:
+The most recent versions of SwiftNIO support Swift 5.5.2 and newer. The minimum Swift version supported by SwiftNIO releases are detailed below:
 
 SwiftNIO            | Minimum Swift Version
 --------------------|----------------------
 `2.0.0 ..< 2.30.0`  | 5.0
 `2.30.0 ..< 2.40.0` | 5.2
 `2.40.0 ..< 2.43.0` | 5.4
-`2.43.0 ...`        | 5.5
+`2.43.0 ...`        | 5.5.2
 
 ### SwiftNIO 1
 SwiftNIO 1 is considered end of life - it is strongly recommended that you move to a newer version.  The Core NIO team does not actively work on this version.  No new features will be added to this version but PRs which fix bugs or security vulnerabilities will be accepted until the end of May 2022.

SECURITY.md

@@ -18,7 +18,7 @@ team would create the following patch releases:
 * NIO 2.42. + plus next patch release to address the issue for projects that support
   Swift 5.4 and later
 * mainline + plus next patch release to address the issue for projects that support
-  Swift 5.5 and later
+  Swift 5.5.2 and later
 
 SwiftNIO 1.x is considered end of life and will not receive any security patches.
 

Sources/NIOAsyncAwaitDemo/AsyncChannelIO.swift

@@ -15,7 +15,6 @@
 import NIOCore
 import NIOHTTP1
 
-#if canImport(_Concurrency) && compiler(>=5.5.2)
 @available(macOS 10.15, iOS 13, tvOS 13, watchOS 6, *)
 struct AsyncChannelIO<Request, Response> {
     let channel: Channel
@@ -39,4 +38,3 @@ struct AsyncChannelIO<Request, Response> {
         try await self.channel.close()
     }
 }
-#endif

Sources/NIOAsyncAwaitDemo/main.swift

@@ -16,8 +16,6 @@ import NIOPosix
 import NIOHTTP1
 import Dispatch
 
-#if canImport(_Concurrency) && compiler(>=5.5.2)
-
 @available(macOS 10.15, iOS 13, tvOS 13, watchOS 6, *)
 func makeHTTPChannel(host: String, port: Int, group: EventLoopGroup) async throws -> AsyncChannelIO<HTTPRequestHead, NIOHTTPClientResponseFull> {
     let channel = try await ClientBootstrap(group: group).connect(host: host, port: port).get()
@@ -76,6 +74,3 @@ if #available(macOS 10.15, iOS 13, tvOS 13, watchOS 6, *) {
     dg.leave()
 }
 dg.wait()
-#else
-print("ERROR: The NIO Async Await Demo supports Swift >= 5.5.2.")
-#endif

Sources/NIOChatServer/main.swift

@@ -109,10 +109,8 @@ final class ChatHandler: ChannelInboundHandler {
     }
 }
 
-#if swift(>=5.5) && canImport(_Concurrency)
 /// access to the internal state is protected by `channelsSyncQueue`
 extension ChatHandler: @unchecked Sendable {}
-#endif
 
 // We need to share the same ChatHandler for all as it keeps track of all
 // connected clients. For this ChatHandler MUST be thread-safe!

Sources/NIOConcurrencyHelpers/NIOAtomic.swift

@@ -313,9 +313,5 @@ public final class NIOAtomic<T: NIOAtomicPrimitive> {
     }
 }
 
-#if compiler(>=5.5) && canImport(_Concurrency)
 @available(*, deprecated)
-extension NIOAtomic: Sendable {
-
-}
-#endif
+extension NIOAtomic: Sendable {}

Sources/NIOConcurrencyHelpers/NIOLock.swift

@@ -147,7 +147,5 @@ extension NIOLock {
     }
 }
 
-#if compiler(>=5.5) && canImport(_Concurrency)
 extension NIOLock: Sendable {}
 extension NIOLock._Storage: Sendable {}
-#endif

Sources/NIOConcurrencyHelpers/NIOLockedValueBox.swift

@@ -52,7 +52,5 @@ public struct NIOLockedValueBox<Value> {
     }
 }
 
-#if compiler(>=5.5) && canImport(_Concurrency)
 extension NIOLockedValueBox: Sendable where Value: Sendable {}
 extension NIOLockedValueBox._Storage: @unchecked Sendable {}
-#endif

Sources/NIOConcurrencyHelpers/lock.swift

@@ -290,12 +290,6 @@ internal func debugOnly(_ body: () -> Void) {
     assert({ body(); return true }())
 }
 
-#if compiler(>=5.5) && canImport(_Concurrency)
 @available(*, deprecated)
-extension Lock: Sendable {
-
-}
-extension ConditionLock: @unchecked Sendable {
-
-}
-#endif
+extension Lock: Sendable {}
+extension ConditionLock: @unchecked Sendable {}

Sources/NIOCore/AsyncAwaitSupport.swift

@@ -12,8 +12,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if compiler(>=5.5.2) && canImport(_Concurrency)
-
 extension EventLoopFuture {
     /// Get the value/error from an `EventLoopFuture` in an `async` context.
     ///
@@ -332,5 +330,3 @@ struct AsyncSequenceFromIterator<AsyncIterator: AsyncIteratorProtocol>: AsyncSeq
         self.iterator
     }
 }
-
-#endif

Sources/NIOCore/AsyncSequences/NIOAsyncSequenceProducer.swift

@@ -12,7 +12,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if compiler(>=5.5.2) && canImport(_Concurrency)
 import DequeModule
 import NIOConcurrencyHelpers
 
@@ -329,4 +328,4 @@ extension NIOAsyncSequenceProducer {
 @available(macOS 10.15, iOS 13, tvOS 13, watchOS 6, *)
 @available(*, unavailable)
 extension NIOAsyncSequenceProducer.AsyncIterator: Sendable {}
-#endif
+

Sources/NIOCore/AsyncSequences/NIOAsyncSequenceProducerStrategies.swift

@@ -12,7 +12,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if compiler(>=5.5.2) && canImport(_Concurrency)
 public enum NIOAsyncSequenceProducerBackPressureStrategies {
     /// A high-low watermarked back-pressure strategy for a ``NIOAsyncSequenceProducer``.
     ///
@@ -46,4 +45,3 @@ public enum NIOAsyncSequenceProducerBackPressureStrategies {
         }
     }
 }
-#endif

Sources/NIOCore/AsyncSequences/NIOAsyncWriter.swift

@@ -12,7 +12,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if compiler(>=5.5.2) && canImport(_Concurrency)
 import Atomics
 import DequeModule
 import NIOConcurrencyHelpers
@@ -1065,4 +1064,3 @@ extension NIOAsyncWriter {
         }
     }
 }
-#endif