Add Swift language version 6 to Swift{Language}Version structs

Author: xedin

Sources/PackageDescription/LanguageStandardSettings.swift

@@ -167,6 +167,10 @@ public enum SwiftVersion {
     @available(_PackageDescription, introduced: 5)
     case v5
 
+    /// The identifier for the Swift 6 language version.
+    @available(_PackageDescription, introduced: 6)
+    case v6
+
     /// A user-defined value for the Swift version.
     ///
     /// The value is passed as-is to the Swift compiler's `-swift-version` flag.
@@ -180,6 +184,7 @@ extension SwiftVersion: CustomStringConvertible {
         case .v4: "4"
         case .v4_2: "4.2"
         case .v5: "5"
+        case .v6: "6"
         case .version(let version): version
         }
     }

Sources/PackageDescription/PackageDescriptionSerialization.swift

@@ -99,6 +99,7 @@ enum Serialization {
         case v4
         case v4_2
         case v5
+        case v6
         case version(String)
     }
 

Sources/PackageDescription/PackageDescriptionSerializationConversion.swift

@@ -112,6 +112,7 @@ extension Serialization.SwiftVersion {
         case .v4: self = .v4
         case .v4_2: self = .v4_2
         case .v5: self = .v5
+        case .v6: self = .v6
         case .version(let version): self = .version(version)
         }
     }

Sources/PackageLoading/ManifestJSONParser.swift

@@ -150,6 +150,7 @@ enum ManifestJSONParser {
             case .v4: languageVersionString = "4"
             case .v4_2: languageVersionString = "4.2"
             case .v5: languageVersionString = "5"
+            case .v6: languageVersionString = "6"
             case .version(let version): languageVersionString = version
             }
             guard let languageVersion = SwiftLanguageVersion(string: languageVersionString) else {

Sources/PackageModel/SwiftLanguageVersion.swift

@@ -31,9 +31,12 @@ public struct SwiftLanguageVersion: Hashable, Sendable {
     /// Swift language version 5.
     public static let v5 = SwiftLanguageVersion(uncheckedString: "5")
 
+    /// Swift language version 6.
+    public static let v6 = SwiftLanguageVersion(uncheckedString: "6")
+
     /// The list of known Swift language versions.
     public static let knownSwiftLanguageVersions = [
-        v3, v4, v4_2, v5,
+        v3, v4, v4_2, v5, v6
     ]
 
     /// The raw value of the language version.

Tests/WorkspaceTests/ManifestSourceGenerationTests.swift

@@ -601,7 +601,7 @@ class ManifestSourceGenerationTests: XCTestCase {
                     name: "v5",
                     type: .executable,
                     settings: [
-                        .init(tool: .swift, kind: .swiftLanguageVersion(.v5))
+                        .init(tool: .swift, kind: .swiftLanguageVersion(.v6))
                     ]
                 ),
                 try TargetDescription(