title: SwiftUI Bindable properties with custom types won't compile
body: <p>I've created a SwiftUI <code>Bindable</code> class with two properties, like</p>
  
  <pre><code>public class Clock: BindableObject {
  
      public let didChange = PassthroughSubject&lt;Clock, Never&gt;()
  
      public var time: Date = Date() {
          didSet { didChange.send(self) }
      }
  
      public var useMilitaryTime = false {
          didSet { didChange.send(self) }
      }
  
  }
  </code></pre>
  
  <p>This works exactly as expected. But when I try to add a property with a custom type (either as a struct, a class, or a tuple), it fails to compile:</p>
  
  <pre><code>    public var sunriseSunset = (Date(), Date()) {
          didSet { didChange(self) }
      }
  </code></pre>
  
  <p>saying I "Cannot call value of non-function type 'PassthroughSubject'". It also fails the same way if I try</p>
  
  <pre><code>    public var sunriseSunset: (Date, Date)? = nil {
          didSet { didChange(self) }
      }
  </code></pre>
  
  <p>The Diagnostics button is unhelpful; it just says that it "Failed to build active schema."</p>
  
  <p>What types can be used as properties of a <code>Bindable</code> class?</p>