loadingviewmodifier.swift

struct LoadingViewModifier: ViewModifier {
    @Binding var isLoading: Bool

    func body(content: Content) -> some View {
        content
            .overlay(
                // Wrapping this in a `Group` fixes the error
                if isLoading {
                    ProgressView()
                        .transition(.opacity) // <-- error: Branches have mismatching types
                                              //  'some View' (result of 'Self.transition') and 
                                              //  'some View' (result of 'Self.transition')
                } else {
                    EmptyView()
                        .transition(.opacity)
                }

            )
    }
}