title: Cannot convert value of type '()' to expected argument type '() -> ()'
body: <p>I am trying to pass a function as a parameter in Swift. In order to do that, I defined my function that takes a callback parameter as:</p>
  
  <pre><code>func foo(callback: () -&gt; () = { _ in }) { callback() }
  </code></pre>
  
  <p>I then define another function that I will use:</p>
  
  <pre><code>func toBeCalled() -&gt; () { 
     print("hello world") 
  }
  
  foo(toBeCalled())
  </code></pre>
  
  <p>I get the following error:</p>
  
  <pre><code>Cannot convert value of type '()' to expected argument type '() -&gt; ()'
  </code></pre>
  
  <p>Has anyone encountered this issue before? I have tried multiple things including using Void.</p>
  
  <p>Thank you!</p>