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, 20 insertions, 0 deletions

diff --git a/test/src/fns-tests.el b/test/src/fns-tests.el
index 79ae4393f40..9c09e4f0c33 100644
--- a/test/src/fns-tests.el
+++ b/test/src/fns-tests.el
@@ -98,6 +98,26 @@
   (should-not (equal-including-properties #("a" 0 1 (k "v"))
                                           #("b" 0 1 (k "v")))))
 
+(ert-deftest fns-tests-equal-symbols-with-position ()
+  "Test `eq' and `equal' on symbols with position."
+  (let ((foo1 (position-symbol 'foo 42))
+        (foo2 (position-symbol 'foo 666))
+        (foo3 (position-symbol 'foo 42)))
+    (let (symbols-with-pos-enabled)
+      (should (eq foo1 foo1))
+      (should (equal foo1 foo1))
+      (should-not (eq foo1 foo2))
+      (should-not (equal foo1 foo2))
+      (should-not (eq foo1 foo3))
+      (should (equal foo1 foo3)))
+    (let ((symbols-with-pos-enabled t))
+      (should (eq foo1 foo1))
+      (should (equal foo1 foo1))
+      (should (eq foo1 foo2))
+      (should (equal foo1 foo2))
+      (should (eq foo1 foo3))
+      (should (equal foo1 foo3)))))
+
 (ert-deftest fns-tests-reverse ()
   (should-error (reverse))
   (should-error (reverse 1))