Call all_type_info_check_for_divergence() also from type_caster_generic::load_impl<>

Author: rwgk

include/pybind11/detail/type_caster_base.h

@@ -785,14 +785,22 @@ class type_caster_generic {
             // if we can find an exact match (or, for a simple C++ type, an inherited match); if
             // so, we can safely reinterpret_cast to the relevant pointer.
             if (bases.size() > 1) {
+                std::vector<type_info *> matching_bases;
                 for (auto *base : bases) {
                     if (no_cpp_mi ? PyType_IsSubtype(base->type, typeinfo->type)
                                   : base->type == typeinfo->type) {
-                        this_.load_value(
-                            reinterpret_cast<instance *>(src.ptr())->get_value_and_holder(base));
-                        return true;
+                        matching_bases.push_back(base);
                     }
                 }
+                if (matching_bases.size() != 0) {
+                    if (matching_bases.size() > 1) {
+                        matching_bases.push_back(const_cast<type_info *>(typeinfo));
+                        all_type_info_check_for_divergence(matching_bases);
+                    }
+                    this_.load_value(reinterpret_cast<instance *>(src.ptr())->get_value_and_holder(
+                        matching_bases[0]));
+                    return true;
+                }
             }
 
             // Case 2c: C++ multiple inheritance is involved and we couldn't find an exact type

tests/test_python_multiple_inheritance.cpp

@@ -61,4 +61,6 @@ TEST_SUBMODULE(python_multiple_inheritance, m) {
         .def("reset_drvd2_value", &CppDrvd2::reset_drvd2_value)
         .def("get_base_value_from_drvd2", &CppDrvd2::get_base_value_from_drvd2)
         .def("reset_base_value_from_drvd2", &CppDrvd2::reset_base_value_from_drvd2);
+
+    m.def("pass_CppBase", [](const CppBase *) {});
 }

tests/test_python_multiple_inheritance.py

@@ -30,6 +30,12 @@ class PCD(PC1, PC2):
     pass
 
 
+class PCDI(PC1, PC2):
+    def __init__(self):
+        PC1.__init__(self, 11)
+        PC2.__init__(self, 12)
+
+
 def test_PC():
     d = PC(11)
     assert d.get_base_value() == 11
@@ -69,3 +75,9 @@ def test_PCD():
         match=r"CppDrvd2\.__init__\(\) must be called when overriding __init__$",
     ):
         PCD(11)
+
+
+def test_PCDI():
+    obj = PCDI()
+    with pytest.raises(TypeError, match="^bases include diverging derived types: "):
+        m.pass_CppBase(obj)