Switch swift-syntax dependency version based on Swift version

Author: andrewheard

FirebaseAI/Tests/Unit/Macros/GenerableMacroTests.swift

@@ -23,15 +23,9 @@
   import XCTest
 
   final class GenerableMacroTests: XCTestCase {
-    #if swift(>=6.2)
-      nonisolated(unsafe) static let testMacros: [String: Macro.Type] = [
-        "stringify": StringifyMacro.self,
-      ]
-    #else
-      static let testMacros: [String: Macro.Type] = [
-        "stringify": StringifyMacro.self,
-      ]
-    #endif // swift(>=6.2)
+    static let testMacros: [String: Macro.Type] = [
+      "stringify": StringifyMacro.self,
+    ]
 
     func testMacro() throws {
       assertMacroExpansion(

Package.swift

@@ -177,7 +177,7 @@ let package = Package(
     ),
     .package(url: "https://github.com/google/app-check.git",
              "11.0.1" ..< "12.0.0"),
-    .package(url: "https://github.com/swiftlang/swift-syntax.git", from: "600.0.0-latest"),
+    swiftSyntaxDependency(),
   ],
   targets: [
     .target(
@@ -1459,6 +1459,17 @@ func grpcDependency() -> Package.Dependency {
   return .package(url: packageInfo.url, packageInfo.range)
 }
 
+func swiftSyntaxDependency() -> Package.Dependency {
+  let url = "https://github.com/swiftlang/swift-syntax.git"
+  #if swift(>=6.2)
+    return .package(url: url, from: "602.0.0-latest")
+  #elseif swift(>=6.1)
+    return .package(url: url, from: "601.0.0-latest")
+  #else
+    return .package(url: url, from: "600.0.0-latest")
+  #endif
+}
+
 func firestoreWrapperTarget() -> Target {
   if Context.environment["FIREBASE_SOURCE_FIRESTORE"] != nil {
     return .target(