Updated to Swift 6 properly

Author: bok-

Package.swift

@@ -23,7 +23,7 @@ let package = Package(
     dependencies: .init {
         Package.Dependency.package(url: "https://github.com/apple/swift-async-algorithms.git", from: "1.0.0")
         Package.Dependency.package(url: "https://github.com/nicklockwood/SwiftFormat.git", from: "0.54.1")
-        Package.Dependency.package(url: "https://github.com/swiftlang/swift-syntax.git", exact: "600.0.0-prerelease-2024-06-12")
+        Package.Dependency.package(url: "https://github.com/swiftlang/swift-syntax.git", .upToNextMajor(from: "600.0.1"))
 
 #if os(Linux)
         // Linux does not come bundled with swift-testing
@@ -43,7 +43,7 @@ let package = Package(
                 .product(name: "AsyncAlgorithms", package: "swift-async-algorithms"),
             ],
             swiftSettings: [
-                .enableExperimentalFeature("StrictConcurrency"),
+                .swiftLanguageMode(.v6),
             ]
         )
         Target.testTarget(
@@ -58,7 +58,7 @@ let package = Package(
 
             },
             swiftSettings: [
-                .enableExperimentalFeature("StrictConcurrency"),
+                .swiftLanguageMode(.v6),
             ]
         )
 
@@ -82,7 +82,7 @@ let package = Package(
                 .product(name: "SwiftSyntaxMacros", package: "swift-syntax"),
             ],
             swiftSettings: [
-                .enableExperimentalFeature("StrictConcurrency"),
+                .swiftLanguageMode(.v6),
             ]
         )
 
@@ -96,15 +96,15 @@ let package = Package(
                 .product(name: "SwiftSyntaxMacrosTestSupport", package: "swift-syntax"),
             ],
             swiftSettings: [
-                .enableExperimentalFeature("StrictConcurrency"),
+                .swiftLanguageMode(.v6),
             ]
         )
 
 #endif
 
     },
 
-    swiftLanguageVersions: [
+    swiftLanguageModes: [
         .v6,
     ]