(function-documentation): Make it work for the remaining cases

* lisp/simple.el (function-documentation):
Use `internal-subr-documentation` and make it work also with symbols
and macros.

* src/doc.c (Fsubr_documentation): New function, extracted
from Fdocumentation.
(syms_of_doc): defsubr it.
(Fdocumentation): Don't handle subrs and module functions here.

2 files changed, 31 insertions, 14 deletions

diff --git a/lisp/simple.el b/lisp/simple.el
index f5712177234..eedc5d7244e 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -2709,7 +2709,16 @@ function as needed."
        (let ((doc (car body)))
 	 (when (funcall docstring-p doc)
            doc)))
-      (_ (signal 'invalid-function (list function))))))
+      ((pred symbolp)
+       (let ((f (indirect-function function)))
+         (if f (function-documentation f)
+           (signal 'void-function (list function)))))
+      (`(macro . ,f) (function-documentation f))
+      (_
+       (let ((doc (internal-subr-documentation function)))
+         (if (eq t doc)
+             (signal 'invalid-function (list function))
+           doc))))))
 
 (cl-defmethod function-documentation ((function accessor))
   (oclosure--accessor-docstring function)) ;; FIXME: η-reduce!
diff --git a/src/doc.c b/src/doc.c
index df57f84603e..174341523d7 100644
--- a/src/doc.c
+++ b/src/doc.c
@@ -330,19 +330,7 @@ string is passed through `substitute-command-keys'.  */)
     xsignal1 (Qvoid_function, function);
   if (CONSP (fun) && EQ (XCAR (fun), Qmacro))
     fun = XCDR (fun);
-#ifdef HAVE_NATIVE_COMP
-  if (!NILP (Fsubr_native_elisp_p (fun)))
-    doc = native_function_doc (fun);
-  else
-#endif
-  if (SUBRP (fun))
-    doc = make_fixnum (XSUBR (fun)->doc);
-#ifdef HAVE_MODULES
-  else if (MODULE_FUNCTIONP (fun))
-    doc = module_function_documentation (XMODULE_FUNCTION (fun));
-#endif
-  else
-    doc = call1 (Qfunction_documentation, fun);
+  doc = call1 (Qfunction_documentation, fun);
 
   /* If DOC is 0, it's typically because of a dumped file missing
      from the DOC file (bug in src/Makefile.in).  */
@@ -371,6 +359,25 @@ string is passed through `substitute-command-keys'.  */)
   return doc;
 }
 
+DEFUN ("internal-subr-documentation", Fsubr_documentation, Ssubr_documentation, 1, 1, 0,
+       doc: /* Return the raw documentation info of a C primitive.  */)
+  (Lisp_Object function)
+{
+#ifdef HAVE_NATIVE_COMP
+  if (!NILP (Fsubr_native_elisp_p (function)))
+    return native_function_doc (function);
+  else
+#endif
+  if (SUBRP (function))
+    return make_fixnum (XSUBR (function)->doc);
+#ifdef HAVE_MODULES
+  else if (MODULE_FUNCTIONP (function))
+    return module_function_documentation (XMODULE_FUNCTION (function));
+#endif
+  else
+    return Qt;
+}
+
 DEFUN ("documentation-property", Fdocumentation_property,
        Sdocumentation_property, 2, 3, 0,
        doc: /* Return the documentation string that is SYMBOL's PROP property.
@@ -713,6 +720,7 @@ compute the correct value for the current terminal in the nil case.  */);
   /* Initialized by ‘main’.  */
 
   defsubr (&Sdocumentation);
+  defsubr (&Ssubr_documentation);
   defsubr (&Sdocumentation_property);
   defsubr (&Ssnarf_documentation);
   defsubr (&Stext_quoting_style);