   (should
    (equal
     (whatif--simplify '(progn nil y) nil)
-    (list 'unknown 'y)))
+    (list 'partial 'y)))
   (should
    (equal
     (whatif--simplify '(progn x nil y) nil)
-    (list 'unknown '(progn x y)))))
+    (list 'partial '(progn x y)))))
 
 (ert-deftest simplify--when ()
   (should

  (should
   (equal
    (whatif--simplify 'x nil)
    (list 'unknown 'x)))
  (should
   (equal
    (whatif--simplify 'x '((x . 42)))

    ;; TODO: update `bindings' after setq.
    (`(setq ,sym ,val)
     (setq val (whatif--simplify val bindings))
     (list 'partial `(setq ,sym ,(cl-second val))))

    (`(or . ,exprs)
     (let (simple-exprs
