PEP 591: Discuss (not doing) runtime final enforcement (#1044)

Co-Authored-By: Ivan Levkivskyi <levkivskyi@gmail.com>

pep-0591.rst

@@ -262,6 +262,17 @@ defined in the same module. Sealed classes seem most useful in
 combination with pattern matching, so it does not seem to justify the
 complexity in our case. This could be revisisted in the future.
 
+It would be possible to have the ``@final`` decorator on classes
+dynamically prevent subclassing at runtime. Nothing else in ``typing``
+does any runtime enforcement, though, so ``final`` will not either.
+A workaround for when both runtime enforcement and static checking is
+desired is to use this idiom (possibly in a support module)::
+
+  if typing.TYPE_CHECKING:
+      from typing import final
+  else:
+      from runtime_final import final
+
 
 References
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