Fix compiling on 6.1

Package.swift

@@ -443,6 +443,7 @@ let package = Package(
                 "NIOConcurrencyHelpers",
                 "NIOEmbedded",
                 "CNIOLinux",
+                "CNIODarwin",
                 "NIOTLS",
             ]
         ),
@@ -558,7 +559,7 @@ let package = Package(
 if Context.environment["SWIFTCI_USE_LOCAL_DEPS"] == nil {
     package.dependencies += [
         .package(url: "https://github.com/apple/swift-atomics.git", from: "1.1.0"),
-        .package(url: "https://github.com/apple/swift-collections.git", from: "1.0.2"),
+        .package(url: "https://github.com/apple/swift-collections.git", from: "1.1.0"),
         .package(url: "https://github.com/apple/swift-system.git", from: "1.4.0"),
     ]
 } else {

Sources/NIOCore/EventLoop.swift

@@ -761,12 +761,13 @@ extension EventLoop {
     /// - Returns: An `EventLoopFuture` containing the result of `task`'s execution.
     @inlinable
     @preconcurrency
-    public func submit<T: Sendable>(_ task: @escaping @Sendable () throws -> T) -> EventLoopFuture<T> {
+    public func submit<T>(_ task: @escaping @Sendable () throws -> T) -> EventLoopFuture<T> {
         let promise: EventLoopPromise<T> = makePromise(file: #fileID, line: #line)
 
         self.execute {
             do {
-                promise.succeed(try task())
+                // UnsafeUnchecked is allowed here because we know we are on the EL.
+                promise.assumeIsolatedUnsafeUnchecked().succeed(try task())
             } catch let err {
                 promise.fail(err)
             }

Sources/NIOCore/FileRegion.swift

@@ -93,9 +93,6 @@ public struct FileRegion: Sendable {
     }
 }
 
-@available(*, unavailable)
-extension FileRegion: Sendable {}
-
 extension FileRegion {
     /// Create a new `FileRegion` forming a complete file.
     ///

Sources/NIOEmbedded/AsyncTestingEventLoop.swift

@@ -131,7 +131,7 @@ public final class NIOAsyncTestingEventLoop: EventLoop, @unchecked Sendable {
         self.scheduledTasks.removeFirst { $0.id == taskID }
     }
 
-    private func insertTask<ReturnType: Sendable>(
+    private func insertTask<ReturnType>(
         taskID: UInt64,
         deadline: NIODeadline,
         promise: EventLoopPromise<ReturnType>,
@@ -145,7 +145,8 @@ public final class NIOAsyncTestingEventLoop: EventLoop, @unchecked Sendable {
             insertOrder: self.nextTaskNumber(),
             task: {
                 do {
-                    promise.succeed(try task())
+                    // UnsafeUnchecked is acceptable because we know we're in the loop here.
+                    promise.assumeIsolatedUnsafeUnchecked().succeed(try task())
                 } catch let err {
                     promise.fail(err)
                 }
@@ -159,7 +160,7 @@ public final class NIOAsyncTestingEventLoop: EventLoop, @unchecked Sendable {
     /// - see: `EventLoop.scheduleTask(deadline:_:)`
     @discardableResult
     @preconcurrency
-    public func scheduleTask<T: Sendable>(
+    public func scheduleTask<T>(
         deadline: NIODeadline,
         _ task: @escaping @Sendable () throws -> T
     ) -> Scheduled<T> {
@@ -201,7 +202,7 @@ public final class NIOAsyncTestingEventLoop: EventLoop, @unchecked Sendable {
     /// - see: `EventLoop.scheduleTask(in:_:)`
     @discardableResult
     @preconcurrency
-    public func scheduleTask<T: Sendable>(in: TimeAmount, _ task: @escaping @Sendable () throws -> T) -> Scheduled<T> {
+    public func scheduleTask<T>(in: TimeAmount, _ task: @escaping @Sendable () throws -> T) -> Scheduled<T> {
         self.scheduleTask(deadline: self.now + `in`, task)
     }
 

Sources/NIOHTTP1/HTTPDecoder.swift

@@ -12,9 +12,14 @@
 //
 //===----------------------------------------------------------------------===//
 
-@_implementationOnly import CNIOLLHTTP
 import NIOCore
 
+#if compiler(>=6.1)
+private import CNIOLLHTTP
+#else
+@_implementationOnly import CNIOLLHTTP
+#endif
+
 extension UnsafeMutablePointer where Pointee == llhttp_t {
     /// Returns the `KeepAliveState` for the current message that is parsed.
     fileprivate var keepAliveState: KeepAliveState {
@@ -631,7 +636,7 @@ public final class HTTPDecoder<In, Out>: ByteToMessageDecoder, HTTPDecoderDelega
         self.url = String(decoding: bytes, as: Unicode.UTF8.self)
     }
 
-    func didFinishHead(
+    fileprivate func didFinishHead(
         versionMajor: Int,
         versionMinor: Int,
         isUpgrade: Bool,
@@ -815,7 +820,7 @@ extension HTTPParserError {
     /// - Parameter fromCHTTPParserErrno: The error from the underlying library.
     /// - Returns: The corresponding `HTTPParserError`, or `nil` if there is no
     ///     corresponding error.
-    static func httpError(fromCHTTPParserErrno: llhttp_errno_t) -> HTTPParserError? {
+    fileprivate static func httpError(fromCHTTPParserErrno: llhttp_errno_t) -> HTTPParserError? {
         switch fromCHTTPParserErrno {
         case HPE_INTERNAL:
             return .invalidInternalState
@@ -874,7 +879,7 @@ extension HTTPMethod {
     ///
     /// - Parameter httpParserMethod: The method returned by `http_parser`.
     /// - Returns: The corresponding `HTTPMethod`.
-    static func from(httpParserMethod: llhttp_method) -> HTTPMethod {
+    fileprivate static func from(httpParserMethod: llhttp_method) -> HTTPMethod {
         switch httpParserMethod {
         case HTTP_DELETE:
             return .DELETE

Sources/NIOPosix/DatagramVectorReadManager.swift

@@ -11,6 +11,7 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+import CNIODarwin
 import CNIOLinux
 import NIOCore
 

Sources/NIOPosix/PendingDatagramWritesManager.swift

@@ -13,6 +13,7 @@
 //===----------------------------------------------------------------------===//
 
 import Atomics
+import CNIODarwin
 import CNIOLinux
 import NIOCore
 

Sources/NIOPosix/SelectableEventLoop.swift

@@ -60,7 +60,7 @@ public protocol NIOEventLoopMetricsDelegate: Sendable {
 /// The whole processing of I/O and tasks is done by a `NIOThread` that is tied to the `SelectableEventLoop`. This `NIOThread`
 /// is guaranteed to never change!
 @usableFromInline
-internal final class SelectableEventLoop: EventLoop {
+internal final class SelectableEventLoop: EventLoop, @unchecked Sendable {
 
     static let strictModeEnabled: Bool = {
         switch getenv("SWIFTNIO_STRICT").map({ String.init(cString: $0).lowercased() }) {

Sources/NIOPosix/SelectorKqueue.swift

@@ -12,6 +12,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+import NIOConcurrencyHelpers
 import NIOCore
 
 #if canImport(Darwin)

Tests/NIOPosixTests/HappyEyeballsTest.swift

@@ -12,6 +12,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+import CNIOLinux
 import NIOEmbedded
 import XCTest
 

Tests/NIOPosixTests/MulticastTest.swift

@@ -11,7 +11,7 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
-
+import CNIOLinux
 import NIOCore
 import NIOPosix
 import XCTest

Tests/NIOPosixTests/PendingDatagramWritesManagerTests.swift

@@ -12,6 +12,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+import CNIODarwin
 import CNIOLinux
 import NIOEmbedded
 import XCTest