shiboken6: Make multiple inheritance cast check less restrictive

The old code would not allow to downcast if a special cast function
exists somewhere in the class hierarchy (as is the case for example
for QWidget inheriting QObject and QPaintDevice).

Make the check more fine-grained by actually checking whether the base
class is a direct, single line inheritance base class of the type
passed in. This makes the mechanism work for widgets.

The corresponding test can then be relaxed.

Task-number: PYSIDE-868
Change-Id: Id81fd9c3080e42009fc84e06a9bab1c8856f2c0c
Reviewed-by: Cristian Maureira-Fredes <cristian.maureira-fredes@qt.io>

1 files changed, 11 insertions, 6 deletions

diff --git a/sources/shiboken6/tests/otherbinding/typediscovery_test.py b/sources/shiboken6/tests/otherbinding/typediscovery_test.py
index 791d3bdce..39dc5cf0f 100644
--- a/sources/shiboken6/tests/otherbinding/typediscovery_test.py
+++ b/sources/shiboken6/tests/otherbinding/typediscovery_test.py
@@ -13,7 +13,8 @@ sys.path.append(os.fspath(Path(__file__).resolve().parents[1]))
 from shiboken_paths import init_paths
 init_paths()
 
-from sample import Abstract, Base1, Derived
+from sample import (Abstract, Base1, Derived,
+                    MDerived1, SonOfMDerived1, MDerived3)
 from other import OtherMultipleDerived
 
 
@@ -32,14 +33,18 @@ class TypeDiscoveryTest(unittest.TestCase):
     def testMultipleInheritance(self):
         obj = OtherMultipleDerived.createObject("Base1")
         self.assertEqual(type(obj), Base1)
-        # PYSIDE-868: In case of multiple inheritance, a factory
-        # function will return the base class wrapper.
+        # PYSIDE-868: In case of single line direct inheritance,
+        # a factory function will return the class wrapper
+        # of the derived class.
         obj = OtherMultipleDerived.createObject("MDerived1")
-        self.assertEqual(type(obj), Base1)
+        self.assertEqual(type(obj), MDerived1)
         obj = OtherMultipleDerived.createObject("SonOfMDerived1")
-        self.assertEqual(type(obj), Base1)
+        self.assertEqual(type(obj), SonOfMDerived1)
         obj = OtherMultipleDerived.createObject("MDerived3")
-        self.assertEqual(type(obj), Base1)
+        self.assertEqual(type(obj), MDerived3)
+        # PYSIDE-868: OtherMultipleDerived inherits
+        # OtherBase, Base1. In this case, a factory
+        # function will return the base class wrapper.
         obj = OtherMultipleDerived.createObject("OtherMultipleDerived")
         self.assertEqual(type(obj), Base1)