anchor.diff:  
   (test-ps-js setf-conditional1
     (setf x (unless (null a) (1+ a)))
  -  "x = a !== null ? a + 1 : null;")
  +  "x = a != null ? a + 1 : null;")
   
   (test-ps-js setf-let1
     (setf x (let ((a 1)) a))
  
positive.code:   (setf x (let ((a (foo)))
              (unless (null a)
                (1+ a))))
    "x = (a = foo(), a !== null ? a + 1 : null);")
  
  (test-ps-js symbol-macro-env1
    (symbol-macrolet ((bar 1))
  
negative.code:   "function blep(ss, x, y) {
      if (foowhat) {
          var pair = bar();
          if (pair != null) {
              var a = pair[0];
              var b = pair[1];
              if (!(a == null || b == null)) {
                  var val = baz(a, b);
                  if (val != null) {
                      if (blah(val)) {
                          if (!blee()) {
                              return true;
  