SwiftUI does not select items with this code

SelectedItems.swift

//
//  SelectedItems.swift
//  OrderedList
//
//  Created by Paul Wood on 8/18/19.
//  Copyright © 2019 Paul Wood. All rights reserved.
//

import SwiftUI
import Combine

class Context: ObservableObject {
  @Published var items: Array<Item>
  @Published var selectedItems: Set<Item>
  
  init() {
    let a = Item("A")
    let b = Item("B")
    let c = Item("C")
    self.items = [a,b,c]
    self.selectedItems = Set([a])
  }
}

struct Item: Identifiable, Hashable {
  public var id: UUID = UUID()
  public var displayText: String
  
  init(_ text: String) {
    self.displayText = text
  }
  
  func hash(into hasher: inout Hasher) {
    hasher.combine(id)
  }
}

struct SelectedItems: View {
  
  @ObservedObject var context: Context
  
  var body: some View {
    NavigationView {
      List (context.items, selection: $context.selectedItems) { item in
        Text(item.displayText)
      }.navigationBarTitle("List")
      .environment(\.editMode, .constant(.active))
    }
  }
}


#if DEBUG
struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
      SelectedItems(context: Context())
    }
}
#endif