title: Kotlin primary constructor calling secondary constructor
body: <p>Why does this not compile?</p>
  
  <pre><code>class test
  {
    constructor() {
        var a = Date().day
        this(a)
    }
  
    constructor(a:Int) {
    }
  }
  </code></pre>
  
  <p>error is:
  Expression 'this' of type 'test' cannot be invoked as a function. The function 'invoke()' is not found.</p>
  
  <p>The suggested fix is to add this:</p>
  
  <pre><code>private operator fun invoke(i: Int) {}
  </code></pre>
  
  <p>Why?</p>