Correct the handling of symbols with position in equal

* src/fns.c (internal_equal): Only regard symbols with position
as their symbols when symbols-with-pos-enabled is non-nil.

* doc/lispref/symbols.texi (Symbols with Position): Expand the
description of symbols with position, in particular the way
they work with eq and equal.

* doc/lispref/objects.texi (Equality Predicates): Describe how
eq and equal handle symbols with position.

* test/src/fns-tests.el (fns-tests-equal-symbols-with-position):
New tests for symbols with position.

1 files changed, 14 insertions, 6 deletions

diff --git a/src/fns.c b/src/fns.c
index ae9969a5432..bd1d63a58c4 100644
--- a/src/fns.c
+++ b/src/fns.c
@@ -2774,10 +2774,13 @@ internal_equal (Lisp_Object o1, Lisp_Object o2, enum equal_kind equal_kind,
 
   /* A symbol with position compares the contained symbol, and is
      `equal' to the corresponding ordinary symbol.  */
-  if (SYMBOL_WITH_POS_P (o1))
-    o1 = SYMBOL_WITH_POS_SYM (o1);
-  if (SYMBOL_WITH_POS_P (o2))
-    o2 = SYMBOL_WITH_POS_SYM (o2);
+  if (symbols_with_pos_enabled)
+    {
+      if (SYMBOL_WITH_POS_P (o1))
+        o1 = SYMBOL_WITH_POS_SYM (o1);
+      if (SYMBOL_WITH_POS_P (o2))
+        o2 = SYMBOL_WITH_POS_SYM (o2);
+    }
 
   if (BASE_EQ (o1, o2))
     return true;
@@ -2825,8 +2828,8 @@ internal_equal (Lisp_Object o1, Lisp_Object o2, enum equal_kind equal_kind,
         if (ASIZE (o2) != size)
           return false;
 
-        /* Compare bignums, overlays, markers, and boolvectors
-           specially, by comparing their values.  */
+        /* Compare bignums, overlays, markers, boolvectors, and
+           symbols with position specially, by comparing their values.  */
         if (BIGNUMP (o1))
           return mpz_cmp (*xbignum_val (o1), *xbignum_val (o2)) == 0;
         if (OVERLAYP (o1))
@@ -2858,6 +2861,11 @@ internal_equal (Lisp_Object o1, Lisp_Object o2, enum equal_kind equal_kind,
         if (TS_NODEP (o1))
           return treesit_node_eq (o1, o2);
 #endif
+        if (SYMBOL_WITH_POS_P(o1)) /* symbols_with_pos_enabled is false.  */
+          return (BASE_EQ (XSYMBOL_WITH_POS (o1)->sym,
+                           XSYMBOL_WITH_POS (o2)->sym)
+                  && BASE_EQ (XSYMBOL_WITH_POS (o1)->pos,
+                              XSYMBOL_WITH_POS (o2)->pos));
 
         /* Aside from them, only true vectors, char-tables, compiled
            functions, and fonts (font-spec, font-entity, font-object)