Add missing type_params attribute for ClassDef node before Python…

…3.12 (#89)

gast/ast3.py

@@ -250,6 +250,19 @@ def visit_AsyncFunctionDef(self, node):
             )
             return gast.copy_location(new_node, node)
 
+    if sys.version_info.minor < 12:
+
+        def visit_ClassDef(self, node):
+            new_node = gast.ClassDef(
+                self._visit(node.name),
+                self._visit(node.bases),
+                self._visit(node.keywords),
+                self._visit(node.body),
+                self._visit(node.decorator_list),
+                [],  # type_params
+            )
+            return gast.copy_location(new_node, node)
+
 
 class GAstToAst3(GAstToAst):
     if sys.version_info.minor < 10:

tests/test_compat.py

@@ -458,6 +458,15 @@ def test_ExtSliceEllipsis(self):
                 "None, type_params=[])], type_ignores=[])")
         self.assertEqual(dump(tree), norm)
 
+    def test_ClassDef(self):
+        code = 'class Foo: pass'
+        tree = gast.parse(code)
+        compile(gast.gast_to_ast(tree), '<test>', 'exec')
+        norm = ("Module(body=[ClassDef(name='Foo', bases=[], keywords=[], "
+                "body=[Pass()], decorator_list=[], type_params=[])], "
+                "type_ignores=[])")
+        self.assertEqual(dump(tree), norm)
+
 
 if __name__ == '__main__':
     unittest.main()