SwiftUI Modifiers on generic Views

I created a control which group a TextField, a Text as the label of the TextField, and eventually a Text to signal an error

The result will be something like that:

To declare this control, I write the following Code:

struct TextFieldWithError<T: Hashable>: View {
    var label: String
    @Binding var text:  String
    @Binding var textError: String
    var focusId:  T?
    @FocusState.Binding var focus: T?

var body: some View {
        VStack {
            HStack {
                if layout == .hstack {
                    Text(label)
                }
                if let focusId {
                    TextField(label, text: $text)
                        .focused($focus, equals: focusId)
                } else {
                    TextField(label, text: $text)
                        .modifier(TextFieldStyle())
                }
            }
            if textError != "" {
                Spacer()
                    .frame(height:2)
                HStack {
                    Text(textError)
                        .foregroundColor(.red)
                        .frame(height: textError == "" ? 0 : 20)
                        .animation(.default)
                }
            }
        }
    }
}

if I use a generic for my control, it's because I want to control focus with the .focused modifier and I didn't found another way to do this

now, I want to control the width of the label with a modifier. I thought about writing

.TextFieldWithErrorFrame(labelWidth: <some CGFloatvalue>)

struct TextFieldWithErrorFrame: ViewModifier {
    varlabelWidth: CGFloat
    func body(content:  Content) -> some View {
        content
    }
}

I think that in place of writing content in the body of my modifier, I have to write the same code that I wrote for the control body, applying a frame modifier on the Label.

But I don't find the way of doing this.

if I declare the modifier as this:

struct TextFieldWithErrorFrame<T>: ViewModifier where T: Hashable {
    var width: CGFloat
    func body(content:  TextFieldWithError<T>) -> some View {
        content
        
    }
}

I need to declare an type alias for the body, because I have the error: Type 'TextFieldWithErrorFrame<T>' does not conform to protocol 'ViewModifier'

if I use

typealias Body = TextFieldWithErrorFrame<T>

I have the same error and that's not all. how to rewrite the content in the body of the modifier?