Bump minimum Swift version to 6.0

Benchmarks/Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:5.10
+// swift-tools-version:6.0
 
 import PackageDescription
 

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:5.10
+// swift-tools-version:6.0
 //===----------------------------------------------------------------------===//
 //
 // This source file is part of the SwiftNIO open source project
@@ -15,24 +15,6 @@
 
 import PackageDescription
 
-let strictConcurrencyDevelopment = false
-
-let strictConcurrencySettings: [SwiftSetting] = {
-    var initialSettings: [SwiftSetting] = []
-    initialSettings.append(contentsOf: [
-        .enableUpcomingFeature("StrictConcurrency"),
-        .enableUpcomingFeature("InferSendableFromCaptures"),
-    ])
-
-    if strictConcurrencyDevelopment {
-        // -warnings-as-errors here is a workaround so that IDE-based development can
-        // get tripped up on -require-explicit-sendable.
-        initialSettings.append(.unsafeFlags(["-Xfrontend", "-require-explicit-sendable", "-warnings-as-errors"]))
-    }
-
-    return initialSettings
-}()
-
 let package = Package(
     name: "swift-nio-ssh",
     platforms: [
@@ -58,8 +40,7 @@ let package = Package(
                 .product(name: "NIOFoundationCompat", package: "swift-nio"),
                 .product(name: "Crypto", package: "swift-crypto"),
                 .product(name: "Atomics", package: "swift-atomics"),
-            ],
-            swiftSettings: strictConcurrencySettings
+            ]
         ),
         .executableTarget(
             name: "NIOSSHClient",
@@ -68,8 +49,7 @@ let package = Package(
                 .product(name: "NIOCore", package: "swift-nio"),
                 .product(name: "NIOPosix", package: "swift-nio"),
                 .product(name: "NIOConcurrencyHelpers", package: "swift-nio"),
-            ],
-            swiftSettings: strictConcurrencySettings
+            ]
         ),
         .executableTarget(
             name: "NIOSSHServer",
@@ -79,8 +59,7 @@ let package = Package(
                 .product(name: "NIOPosix", package: "swift-nio"),
                 .product(name: "NIOFoundationCompat", package: "swift-nio"),
                 .product(name: "Crypto", package: "swift-crypto"),
-            ],
-            swiftSettings: strictConcurrencySettings
+            ]
         ),
         .executableTarget(
             name: "NIOSSHPerformanceTester",
@@ -89,8 +68,7 @@ let package = Package(
                 .product(name: "NIOCore", package: "swift-nio"),
                 .product(name: "NIOEmbedded", package: "swift-nio"),
                 .product(name: "Crypto", package: "swift-crypto"),
-            ],
-            swiftSettings: strictConcurrencySettings
+            ]
         ),
         .testTarget(
             name: "NIOSSHTests",
@@ -99,8 +77,7 @@ let package = Package(
                 .product(name: "NIOCore", package: "swift-nio"),
                 .product(name: "NIOEmbedded", package: "swift-nio"),
                 .product(name: "NIOFoundationCompat", package: "swift-nio"),
-            ],
-            swiftSettings: strictConcurrencySettings
+            ]
         ),
     ]
 )

README.md

@@ -21,7 +21,8 @@ SwiftNIO SSH        | Minimum Swift Version
 `0.6.2  ..< 0.9.0`  | 5.6
 `0.9.0  ..< 0.9.2`  | 5.8
 `0.9.2  ..< 0.10.0` | 5.9
-`0.10.0 ...`        | 5.10
+`0.10.0 ... 0.12.0` | 5.10
+`0.12.0 ...`        | 6.0
 
 ## What does SwiftNIO SSH support?
 

Sources/NIOSSH/Connection State Machine/Operations/AcceptsUserAuthMessages.swift

@@ -14,7 +14,7 @@
 
 import NIOCore
 
-protocol AcceptsUserAuthMessages {
+protocol AcceptsUserAuthMessages: _NIOSSHSendableMetatype {
     var userAuthStateMachine: UserAuthenticationStateMachine { get set }
 
     var role: SSHConnectionRole { get }

Sources/NIOSSH/Key Exchange/EllipticCurveKeyExchange.swift

@@ -24,7 +24,7 @@ import Foundation
 
 /// This protocol defines a container used by the key exchange state machine to manage key exchange.
 /// This type erases the specific key exchanger.
-protocol EllipticCurveKeyExchangeProtocol {
+protocol EllipticCurveKeyExchangeProtocol: _NIOSSHSendableMetatype {
     init(ourRole: SSHConnectionRole, previousSessionIdentifier: ByteBuffer?)
 
     func initiateKeyExchangeClientSide(allocator: ByteBufferAllocator) -> SSHMessage.KeyExchangeECDHInitMessage

Sources/NIOSSH/TransportProtection/SSHTransportProtection.swift

@@ -44,7 +44,7 @@ import NIOCore
 /// Implementers of this protocol **must not** expose unauthenticated plaintext, except for the length field. This
 /// is required by the SSH protocol, and swift-nio-ssh does its best to treat the length field as fundamentally
 /// untrusted information.
-public protocol NIOSSHTransportProtection: AnyObject {
+public protocol NIOSSHTransportProtection: AnyObject, _NIOSSHSendableMetatype {
     /// The name of the cipher portion of this transport protection scheme as negotiated on the wire.
     static var cipherName: String { get }
 

Sources/NIOSSH/_NIOSSHSendableMetatype.swift

@@ -0,0 +1,19 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftNIO open source project
+//
+// Copyright (c) 2019-2020 Apple Inc. and the SwiftNIO project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftNIO project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+#if compiler(>=6.2)
+@_marker public protocol _NIOSSHSendableMetatype: SendableMetatype {}
+#else
+@_marker public protocol _NIOSSHSendableMetatype {}
+#endif