New helper function assq_no_signal

* src/fns.c (assq_no_signal): New function.
* src/lisp.h (assoc_no_signal): Declare it.
* src/treesit.c (safe_assq): Remove function.
(treesit_traverse_get_predicate): Change safe_assq to assq_no_signal.

src/fns.c

@@ -1966,6 +1966,20 @@ assq_no_quit (Lisp_Object key, Lisp_Object alist)
   return Qnil;
 }
 
+/* Assq but doesn't signal.  Unlike assq_no_quit, this function still
+   detect circular lists; like assq_no_quit, this function does not
+   allow quits and never signals.  If anything goes wrong, it returns
+   Qnil.  */
+Lisp_Object
+assq_no_signal (Lisp_Object key, Lisp_Object alist)
+{
+  Lisp_Object tail = alist;
+  FOR_EACH_TAIL_SAFE (tail)
+    if (CONSP (XCAR (tail)) && EQ (XCAR (XCAR (tail)), key))
+      return XCAR (tail);
+  return Qnil;
+}
+
 DEFUN ("assoc", Fassoc, Sassoc, 2, 3, 0,
        doc: /* Return non-nil if KEY is equal to the car of an element of ALIST.
 The value is actually the first element of ALIST whose car equals KEY.

src/lisp.h

@@ -4031,6 +4031,7 @@ extern Lisp_Object concat3 (Lisp_Object, Lisp_Object, Lisp_Object);
 extern bool equal_no_quit (Lisp_Object, Lisp_Object);
 extern Lisp_Object nconc2 (Lisp_Object, Lisp_Object);
 extern Lisp_Object assq_no_quit (Lisp_Object, Lisp_Object);
+extern Lisp_Object assq_no_signal (Lisp_Object, Lisp_Object);
 extern Lisp_Object assoc_no_quit (Lisp_Object, Lisp_Object);
 extern void clear_string_char_byte_cache (void);
 extern ptrdiff_t string_char_to_byte (Lisp_Object, ptrdiff_t);

src/treesit.c

@@ -3153,17 +3153,6 @@ treesit_traverse_child_helper (TSTreeCursor *cursor,
     }
 }
 
-/* Assq but doesn't signal.  */
-static Lisp_Object
-safe_assq (Lisp_Object key, Lisp_Object alist)
-{
-  Lisp_Object tail = alist;
-  FOR_EACH_TAIL_SAFE (tail)
-    if (CONSP (XCAR (tail)) && EQ (XCAR (XCAR (tail)), key))
-      return XCAR (tail);
-  return Qnil;
-}
-
 /* Given a symbol THING, and a language symbol LANGUAGE, find the
    corresponding predicate definition in treesit-things-settings.
    Don't check for the type of THING and LANGUAGE.
@@ -3172,11 +3161,11 @@ safe_assq (Lisp_Object key, Lisp_Object alist)
 static Lisp_Object
 treesit_traverse_get_predicate (Lisp_Object thing, Lisp_Object language)
 {
-  Lisp_Object cons = safe_assq (language, Vtreesit_thing_settings);
+  Lisp_Object cons = assq_no_quit (language, Vtreesit_thing_settings);
   if (NILP (cons))
     return Qnil;
   Lisp_Object definitions = XCDR (cons);
-  Lisp_Object entry = safe_assq (thing, definitions);
+  Lisp_Object entry = assq_no_quit (thing, definitions);
   if (NILP (entry))
     return Qnil;
   /* ENTRY looks like (THING PRED).  */