title: Strange definition method (def) in Groovy. Looks like an object or function with no name
body: <p>I came across this in code a few times, and cannot figure out what this declaration is exactly. It appears to simply be a collection of variables, but is being passed together as though it is some singular variable or object itself holding all 3 values. 
  What exactly is this?</p>
  
  <pre><code>def foo(filename) {
      // Below you can find an assignment I don't understand:
      def (id, company, type) = roo(filename)
      AClass.findByStuff(id, company, type)
  }
  </code></pre>