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