Fix incorrect operator lookup for postincrement (#4536)

Fix incorrect operator lookup for postincrement. Before this Cython always called the c++ "preincrement" operator.

1 files changed, 13 insertions, 0 deletions

diff --git a/docs/src/userguide/migrating_to_cy30.rst b/docs/src/userguide/migrating_to_cy30.rst
index 50b0b6734..292a2e943 100644
--- a/docs/src/userguide/migrating_to_cy30.rst
+++ b/docs/src/userguide/migrating_to_cy30.rst
@@ -226,3 +226,16 @@ To make it easier to handle cases where your interpretation of type
 annotations differs from Cython's, Cython 3 now supports setting the
 ``annotation_typing`` :ref:`directive <compiler-directives>` on a
 per-class or per-function level.
+
+C++ postincrement/postdecrement operator
+========================================
+
+Cython 3 differentiates between pre/post-increment and pre/post-decrement
+operators (Cython 0.29 implemented both as pre(in/de)crement operator).
+This only has an effect when using ``cython.operator.postdecrement`` / ``cython.operator.postincrement``.
+When running into an error it is required to add the corresponding operator::
+
+    cdef cppclass Example:
+        Example operator++(int)
+        Example operator--(int)
+