Re-add "c_api_binop_methods" directive for backwards compatibility after...

Re-add "c_api_binop_methods" directive for backwards compatibility after reverting https://github.com/cython/cython/pull/3633 and force it to "False".
Closes #3688.

CHANGES.rst

@@ -8,6 +8,9 @@ Cython Changelog
 Bugs fixed
 ----------
 
+* Fix a regression in 0.29.20 where ``__div__`` failed to be found in extension types.
+  (Github issue #3688)
+
 * The deprecated C-API function ``PyUnicode_FromUnicode()`` is no longer used.
   Original patch by Inada Naoki.  (Github issue #3677)
 

Cython/Compiler/ModuleNode.py

@@ -1223,6 +1223,10 @@ class ModuleNode(Nodes.Node, Nodes.BlockNode):
                 type = entry.type
                 scope = type.scope
                 if scope: # could be None if there was an error
+                    if not scope.directives['c_api_binop_methods']:
+                        error(self.pos,
+                              "The 'c_api_binop_methods' directive is only supported for forward compatibility"
+                              " and must be True.")
                     self.generate_exttype_vtable(scope, code)
                     self.generate_new_function(scope, code, entry)
                     self.generate_dealloc_function(scope, code)

Cython/Compiler/Options.py

@@ -178,6 +178,7 @@ _directive_defaults = {
     'auto_pickle': None,
     'cdivision': False,  # was True before 0.12
     'cdivision_warnings': False,
+    'c_api_binop_methods': True,
     'overflowcheck': False,
     'overflowcheck.fold': True,
     'always_allow_keywords': False,