Ensure we handle aliased primitive functions

Fixes #34

3 files changed, 17 insertions, 1 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a27be4a..0a757de 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,7 @@
 # v0.2
 
+Fixed a crash on viewing aliased primitive functions.
+
 Fixed an issue where we didn't find the path for functions defined
 interactively using `cl-defstruct`.
 
diff --git a/helpful.el b/helpful.el
index 37daee4..8be3865 100644
--- a/helpful.el
+++ b/helpful.el
@@ -515,7 +515,13 @@ POSITION-HEADS takes the form ((123 (defun foo)) (456 (defun bar)))."
 (defun helpful--primitive-p (sym callable-p)
   "Return t if SYM is defined in C."
   (if callable-p
-      (subrp (symbol-function sym))
+      (let ((fn sym))
+        ;; Find the function value associated with this symbol. If
+        ;; it's an alias, follow the alias chain to the function
+        ;; value.
+        (while (symbolp fn)
+          (setq fn (symbol-function fn)))
+        (subrp fn))
     (let ((filename (find-lisp-object-file-name sym 'defvar)))
       (or (eq filename 'C-source)
           (and (stringp filename)
diff --git a/test/unit-test.el b/test/unit-test.el
index 8e5349a..943e981 100644
--- a/test/unit-test.el
+++ b/test/unit-test.el
@@ -49,6 +49,14 @@
 (defun test-foo-no-properties ()
   nil)
 
+(ert-deftest helpful--primitive-p ()
+  ;; Defined in C.
+  (should (helpful--primitive-p 'message t))
+  ;; Defined in C, but an alias.
+  (should (helpful--primitive-p 'not t))
+  ;; Defined in elisp.
+  (should (not (helpful--primitive-p 'when t))))
+
 (ert-deftest helpful--no-symbol-properties ()
   "Helpful should handle functions without any symbol properties."
   ;; Interactively evaluating this file will set edebug properties on