Proper variable/function hoisting

[y21]

Declaration hoisting partly works already (you can refer to a var before it is used, containing the undefined value if uninitialized). Function declarations work different however in that they are immediately initialized with the function and you can call them even before their declarations are "reached":

(function() {
  return b();

  var a = c();
  function b() {
    return c();
  }
  function c() {
    return 3;
  }
})()

Semantics should be equivalent to this:

(function() {
  // Functions declarations
  var b;
  var c;
  // Variable declarations
  var a;
  // Function initialization
  b = function() {
    return c();
  }
  c = function() {
    return 3;
  }

  return b();
  // Definition stays
  a = c();
})();