Add minimal tests.

tests/CMakeLists.txt

@@ -178,6 +178,7 @@ set(PYBIND11_TEST_FILES
     test_stl_binders
     test_tagbased_polymorphic
     test_thread
+    test_type_caster_addressof
     test_type_caster_odr_guard_1
     test_type_caster_odr_guard_2
     test_type_caster_pyobject_ptr

tests/test_type_caster_addressof.cpp

@@ -0,0 +1,35 @@
+#include <pybind11/smart_holder.h>
+
+#include "pybind11_tests.h"
+
+namespace pybind11_tests {
+namespace type_caster_addressof {
+
+struct UnusualOpRefReturnType {};
+
+template <int> // Using int as a trick to easily generate a series of types.
+struct UnusualOpRef {
+    UnusualOpRefReturnType operator&() { return UnusualOpRefReturnType(); }
+};
+
+} // namespace type_caster_addressof
+} // namespace pybind11_tests
+
+PYBIND11_SMART_HOLDER_TYPE_CASTERS(pybind11_tests::type_caster_addressof::UnusualOpRef<1>)
+
+namespace pybind11_tests {
+namespace type_caster_addressof {
+
+py::object PassMovable0(UnusualOpRef<0> &&mvbl) { return py::cast(std::move(mvbl)); }
+py::object PassMovable1(UnusualOpRef<1> &&mvbl) { return py::cast(std::move(mvbl)); }
+
+} // namespace type_caster_addressof
+} // namespace pybind11_tests
+
+TEST_SUBMODULE(type_caster_addressof, m) {
+    using namespace pybind11_tests::type_caster_addressof;
+    py::class_<UnusualOpRef<0>>(m, "UnusualOpRef0");
+    py::classh<UnusualOpRef<1>>(m, "UnusualOpRef1");
+    m.def("CallPassMovable0", []() { return PassMovable0(UnusualOpRef<0>()); });
+    m.def("CallPassMovable1", []() { return PassMovable1(UnusualOpRef<1>()); });
+}

tests/test_type_caster_addressof.py

@@ -0,0 +1,6 @@
+from pybind11_tests import type_caster_addressof as m
+
+
+def test_merely_that_it_actually_built():
+    assert m.CallPassMovable0().__class__.__name__ == "UnusualOpRef0"
+    assert m.CallPassMovable1().__class__.__name__ == "UnusualOpRef1"