Detect aliases to built-in functions

* lisp/help-fns.el (describe-function-1): Check for aliases
defined with (defalias alias (symbol-function built-in)) (Bug#23887).

* test/lisp/help-fns-tests.el (help-fns-test-bug23887): Untag as
failing this test.

1 files changed, 10 insertions, 6 deletions

diff --git a/lisp/help-fns.el b/lisp/help-fns.el
index 9464c0b0d97..e4e23330e37 100644
--- a/lisp/help-fns.el
+++ b/lisp/help-fns.el
@@ -572,13 +572,17 @@ FILE is the file where FUNCTION was probably defined."
          (aliased (or (symbolp def)
                       ;; Advised & aliased function.
                       (and advised (symbolp real-function)
-                           (not (eq 'autoload (car-safe def))))))
+                           (not (eq 'autoload (car-safe def))))
+                      (and (subrp def)
+                           (not (string= (subr-name def)
+                                         (symbol-name function))))))
          (real-def (cond
-                    (aliased (let ((f real-function))
-                               (while (and (fboundp f)
-                                           (symbolp (symbol-function f)))
-                                 (setq f (symbol-function f)))
-                               f))
+                    ((and aliased (not (subrp def)))
+                     (let ((f real-function))
+                       (while (and (fboundp f)
+                                   (symbolp (symbol-function f)))
+                         (setq f (symbol-function f)))
+                       f))
                     ((subrp def) (intern (subr-name def)))
                     (t def)))
          (sig-key (if (subrp def)