Subclasses of string can no longer be interned. The semantics of
interning were not clear here -- a subclass could be mutable, for
example -- and had bugs. Explicitly interning a subclass of string
via intern() will raise a TypeError. Internal operations that attempt
to intern a string subclass will have no effect.
Added a few tests to test_builtin that includes the old buggy code and
verifies that calls like PyObject_SetAttr() don't fail. Perhaps these
tests should have gone in test_string.
diff --git a/Misc/NEWS b/Misc/NEWS
index 9f80274..7550076 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,12 @@
Core and builtins
-----------------
+Subclasses of string can no longer be interned. The semantics of
+interning were not clear here -- a subclass could be mutable, for
+example -- and had bugs. Explicitly interning a subclass of string
+via intern() will raise a TypeError. Internal operations that attempt
+to intern a string subclass will have no effect.
+
Extension modules
-----------------