Test to trigger a style-warning - (values) should match a T|NIL return.

> Result is a (VALUES &OPTIONAL), not a (VALUES BOOLEAN &OPTIONAL).

tests/compiler.impure.lisp

@@ -2286,6 +2286,21 @@
                (length (clear-derived-types-on-set-fdefn-1)))))
     (assert (= 6 (clear-derived-types-on-set-fdefn-2)))))
 
+
+(declaim (ftype (function () (values (member t nil) &optional)) values-is-a-boolean-return))
+(test-util:with-test (:name :values-is-a-boolean-return)
+(let* ((*evaluator-mode* :compile)
+       (*derive-function-types* t)
+       (compiler-result
+         (with-output-to-string (*error-output*)
+           (eval `(progn
+                    (defun values-is-a-boolean-return ()
+                      (if (zerop (random 2))
+                          (values)))))
+           )))
+  (assert (string= "" compiler-result))))
+
+
 (test-util:with-test (:name (:bug-655126 :derive-function-types t))
   (let ((*evaluator-mode* :compile)
         (*derive-function-types* t))