Symplify (not t) => nil and (not nil) => t

* lisp/emacs-lisp/comp-cstr.el (comp-cstr-negation): Symplify (not
	t) => nil and (not nil) => t.
	* test/lisp/emacs-lisp/comp-cstr-tests.el
	(comp-cstr-typespec-tests-alist): Add two tests.

lisp/emacs-lisp/comp-cstr.el

@@ -695,10 +695,27 @@ DST is returned."
   "Negate SRC setting the result in DST.
 DST is returned."
   (with-comp-cstr-accessors
-    (setf (typeset dst) (typeset src)
-          (valset dst) (valset src)
-          (range dst) (range src)
-          (neg dst) (not (neg src)))
+    (cond
+     ((and (null (valset src))
+           (null (range src))
+           (null (neg src))
+           (equal (typeset src) '(t)))
+      (setf (typeset dst) ()
+            (valset dst) ()
+            (range dst) nil
+            (neg dst) nil))
+     ((and (null (valset src))
+           (null (range src))
+           (null (neg src))
+           (null (typeset src)))
+      (setf (typeset dst) '(t)
+            (valset dst) ()
+            (range dst) nil
+            (neg dst) nil))
+     (t (setf (typeset dst) (typeset src)
+              (valset dst) (valset src)
+              (range dst) (range src)
+              (neg dst) (not (neg src)))))
     dst))
 
 (defun comp-cstr-value-negation (dst src)

test/lisp/emacs-lisp/comp-cstr-tests.el

@@ -203,7 +203,11 @@
       ;; 81
       ((and t (not t)) . nil)
       ;; 82
-      ((or (integer 1 1) (not (integer 1 1))) . t))
+      ((or (integer 1 1) (not (integer 1 1))) . t)
+      ;; 83
+      ((not t) . nil)
+      ;; 84
+      ((not nil) . t))
     "Alist type specifier -> expected type specifier."))
 
 (defmacro comp-cstr-synthesize-tests ()