[SwiftUI] マルチプラットフォーム 対応しつつ view modifier を適用する

#if os(iOS)
何らかの処理
#endif

struct ContentView: View {
    @State private var data = ["Item1", "Item2", "Item3", "Item4"]
    var body: some View {
        VStack {
#if os(iOS)
            EditButton()
#endif
            List {
                ForEach(data, id:\.self) { title in
                    HStack {
                        Text("Title: \(title)")
                    }
                }
                .onDelete(perform: { indexSet in
                    data.remove(at: indexSet.first!)
                })
                .onMove(perform: { indices, newOffset in
                    withAnimation {
                        data.move(fromOffsets: indices, toOffset: newOffset)
                    }
                })
            }
        #if os(iOS)
            .environment(\.editMode, .constant(.active))
        #endif    // -  エラー  Unexpected platform condition(expected 'ios', 'arch', or 'swift')
        }
    }
}

struct onlyiOSModifier: ViewModifier {
    func body(content: Content) -> some View {
        #if os(iOS)
        return content.environment(\.editMode, .constant(.active))
        #else
        return content
        #endif
    }
}

        List {
          // .. snip
        }
        .modifier(onlyiOSModifier())

enum OperatingSystem {
    case macOS
    case iOS
    case tvOS
    case watchOS
    #if os(macOS)
    static let current = macOS
    #elseif os(iOS)
    static let current = iOS
    #elseif os(tvOS)
    static let current = tvOS
    #elseif os(watchOS)
    static let current = watchOS
    #else
    #error("Unsupported platform")
    #endif
}

extension View {
    @ViewBuilder
    func applyOSModifier() -> some View {
        switch OperatingSystem.current {
            case .iOS:
                self.modifier(iOSOnlyModifier())
            default:
                self
        }
    }
}

        List {
          // .. snip
        }
        .applyOSModifier()