NavigationView_Issue.swift

import SwiftUI

struct ContentView: View {
  @State var flag = true

  var body: some View {
    let text = "\(flag ? "HStack" : "ZStack")"
    return VStack {
      Text(text)
      Button("change the stack") {
        self.flag.toggle()
      }
      Layout(flag: flag) {
        NavigationView {
          NavigationLink(destination: A()) {
            Text("move to A")
          }
        }
      }
    }
  }
}

struct A: View {
  var body: some View {
    NavigationLink(destination: B()) {
      Text("move to B")
    }
  }
}

struct B: View {
  var body: some View {
    Text("B")
  }
}

struct Layout<Content>: View where Content: View {
  var flag: Bool
  var content: Content

  init(flag: Bool, content: () -> Content) {
    self.flag = flag
    self.content = content()
  }

  var hStack: some View {
    HStack
      {
        content
      }
      .border(Color.red)
  }
  var zStack: some View {
    ZStack
      {
        content
      }
      .border(Color.green)
  }

  @ViewBuilder
  var body: some View {
    if flag {
      hStack
    } else {
      zStack
    }
  }
}

struct ContentView_Previews: PreviewProvider {
  static var previews: some View {
    ContentView()
  }
}