Issue #12067: Recommend that hash and equality be consistent
diff --git a/Doc/reference/expressions.rst b/Doc/reference/expressions.rst
index 9792399..ea89486 100644
--- a/Doc/reference/expressions.rst
+++ b/Doc/reference/expressions.rst
@@ -1255,6 +1255,10 @@
sequences, but not to sets or mappings). See also the
:func:`~functools.total_ordering` decorator.
+* The :func:`hash` result should be consistent with equality.
+ Objects that are equal should either have the same hash value,
+ or be marked as unhashable.
+
Python does not enforce these consistency rules. In fact, the not-a-number
values are an example for not following these rules.