title: Xcode "Playground execution failed: error: Couldn't lookup symbols"
body: <p>I'm trying to set up a playground for a Swift framework I'm working on. I've followed the steps in <a href="https://stackoverflow.com/a/33451726/6348578">this answer</a> but trying to access members of the framework stops playground execution and throws:</p>
  
  <pre><code>Playground execution failed: error: Couldn't lookup symbols:
  __symbol1...
  __symbol2...
  ...
  </code></pre>
  
  <p>I've made sure that the members are public. I can import the module itself and Xcode even shows code completion for the members, but the playground itself won't run because of the error.</p>