def_readwrite/readonly: bind using class type, not inferred type

include/pybind11/pybind11.h

@@ -1042,15 +1042,17 @@ class class_ : public detail::generic_type {
 
     template <typename C, typename D, typename... Extra>
     class_ &def_readwrite(const char *name, D C::*pm, const Extra&... extra) {
-        cpp_function fget([pm](const C &c) -> const D &{ return c.*pm; }, is_method(*this)),
-                     fset([pm](C &c, const D &value) { c.*pm = value; }, is_method(*this));
+        static_assert(std::is_base_of<C, type>::value, "def_readwrite() requires a class member (or base class member)");
+        cpp_function fget([pm](const type &c) -> const D &{ return c.*pm; }, is_method(*this)),
+                     fset([pm](type &c, const D &value) { c.*pm = value; }, is_method(*this));
         def_property(name, fget, fset, return_value_policy::reference_internal, extra...);
         return *this;
     }
 
     template <typename C, typename D, typename... Extra>
     class_ &def_readonly(const char *name, const D C::*pm, const Extra& ...extra) {
-        cpp_function fget([pm](const C &c) -> const D &{ return c.*pm; }, is_method(*this));
+        static_assert(std::is_base_of<C, type>::value, "def_readonly() requires a class member (or base class member)");
+        cpp_function fget([pm](const type &c) -> const D &{ return c.*pm; }, is_method(*this));
         def_property_readonly(name, fget, return_value_policy::reference_internal, extra...);
         return *this;
     }

tests/test_methods_and_attributes.cpp

@@ -102,6 +102,9 @@ struct TestPropRVP {
 SimpleValue TestPropRVP::sv1{};
 SimpleValue TestPropRVP::sv2{};
 
+struct UnregisteredBaseWithMember { int ro = 6; int rw = 13; };
+struct RegisteredDerivedInheritsMember : UnregisteredBaseWithMember {};
+
 class DynamicClass {
 public:
     DynamicClass() { print_default_created(this); }
@@ -258,6 +261,16 @@ test_initializer methods_and_attributes([](py::module &m) {
     py::class_<SimpleValue>(m, "SimpleValue")
         .def_readwrite("value", &SimpleValue::value);
 
+    // Unnumbered issue: can't expose unregistered base class member with def_readwrite/def_readonly
+    py::class_<RegisteredDerivedInheritsMember>(m, "RegisteredDerivedInheritsMember")
+        .def(py::init<>())
+        .def_readonly("ro", &UnregisteredBaseWithMember::ro)
+        .def_readwrite("rw", &UnregisteredBaseWithMember::rw)
+        // These should trigger a static_assert if uncommented
+        //.def_readwrite("fails", &SimpleValue::value) // should trigger a static_assert if uncommented
+        //.def_readonly("fails", &SimpleValue::value) // should trigger a static_assert if uncommented
+        ;
+
     auto static_get1 = [](py::object) -> const SimpleValue & { return TestPropRVP::sv1; };
     auto static_get2 = [](py::object) -> const SimpleValue & { return TestPropRVP::sv2; };
     auto static_set1 = [](py::object, int v) { TestPropRVP::sv1.value = v; };

tests/test_methods_and_attributes.py

@@ -61,7 +61,7 @@ def test_methods_and_attributes():
 
 
 def test_properties():
-    from pybind11_tests import TestProperties
+    from pybind11_tests import TestProperties, RegisteredDerivedInheritsMember
 
     instance = TestProperties()
 
@@ -79,6 +79,12 @@ def test_properties():
     instance.def_property = 3
     assert instance.def_property == 3
 
+    z = RegisteredDerivedInheritsMember()
+    assert z.ro == 6
+    assert z.rw == 13
+    z.rw += z.ro
+    assert z.ro == 6 and z.rw == 19
+
 
 def test_copy_method():
     """Issue #443: calling copied methods fails in Python 3"""