title: Create keypath based on parameter
body: <p>I got this code:</p>
  
  <pre><code>class Person {
      let age = 0
  }
  
  func createKeyPath() {
      let ageKeyPath = \Person.age // Works
  }
  
  func createKeyPath(from: ???) { // What can I place here to make it compile?
      let ageKeyPath = \from.age
  }
  </code></pre>
  
  <p>I got generic classes and I need to create keypaths on a generic concrete type (like Person), but I am not sure how I can create keypaths based on a parameter. I tried:</p>
  
  <pre><code>func createKeyPath(from: Person.Type) {
      let ageKeyPath = \from.age
  }
  </code></pre>
  
  <p>But it doesn't compile.</p>