Fix implicit conversion of accessors to types derived from py::object

Fixes #1069.

include/pybind11/pytypes.h

@@ -431,8 +431,8 @@ class accessor : public object_api<accessor<Policy>> {
 
 public:
     accessor(handle obj, key_type key) : obj(obj), key(std::move(key)) { }
-    accessor(const accessor &a) = default;
-    accessor(accessor &&a) = default;
+    accessor(const accessor &) = default;
+    accessor(accessor &&) = default;
 
     // accessor overload required to override default assignment operator (templates are not allowed
     // to replace default compiler-generated assignments).
@@ -743,7 +743,9 @@ NAMESPACE_END(detail)
     { if (!m_ptr) throw error_already_set(); } \
     Name(object &&o) \
     : Parent(check_(o) ? o.release().ptr() : ConvertFun(o.ptr()), stolen_t{}) \
-    { if (!m_ptr) throw error_already_set(); }
+    { if (!m_ptr) throw error_already_set(); } \
+    template <typename Policy_> \
+    Name(const ::pybind11::detail::accessor<Policy_> &a) : Name(object(a)) { }
 
 #define PYBIND11_OBJECT(Name, Parent, CheckFun) \
     PYBIND11_OBJECT_COMMON(Name, Parent, CheckFun) \

tests/test_pytypes.cpp

@@ -128,6 +128,12 @@ TEST_SUBMODULE(pytypes, m) {
         d["operator()"] = o.attr("func")(1);
         d["operator*"] = o.attr("func")(*o.attr("begin_end"));
 
+        // Test implicit conversion
+        py::list implicit_list = o.attr("begin_end");
+        d["implicit_list"] = implicit_list;
+        py::dict implicit_dict = o.attr("__dict__");
+        d["implicit_dict"] = implicit_dict;
+
         return d;
     });
 

tests/test_pytypes.py

@@ -144,6 +144,8 @@ def test_accessors():
     assert d["is_none"] is False
     assert d["operator()"] == 2
     assert d["operator*"] == 7
+    assert d["implicit_list"] == [1, 2, 3]
+    assert all(x in TestObject.__dict__ for x in d["implicit_dict"])
 
     assert m.tuple_accessor(tuple()) == (0, 1, 2)