Set __hash__ to None for types that defines __eq__, but not __hash__ (#2291)
fixes #2191
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 1a415a4..87f4645 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -1047,6 +1047,13 @@
#endif
}
+inline void add_class_method(object& cls, const char *name_, const cpp_function &cf) {
+ cls.attr(cf.name()) = cf;
+ if (strcmp(name_, "__eq__") == 0 && !cls.attr("__dict__").contains("__hash__")) {
+ cls.attr("__hash__") = none();
+ }
+}
+
PYBIND11_NAMESPACE_END(detail)
/// Given a pointer to a member function, cast it to its `Derived` version.
@@ -1144,7 +1151,7 @@
class_ &def(const char *name_, Func&& f, const Extra&... extra) {
cpp_function cf(method_adaptor<type>(std::forward<Func>(f)), name(name_), is_method(*this),
sibling(getattr(*this, name_, none())), extra...);
- attr(cf.name()) = cf;
+ add_class_method(*this, name_, cf);
return *this;
}
diff --git a/tests/test_operator_overloading.cpp b/tests/test_operator_overloading.cpp
index 52fcd33..f3c2eaa 100644
--- a/tests/test_operator_overloading.cpp
+++ b/tests/test_operator_overloading.cpp
@@ -187,6 +187,38 @@
.def(py::self *= int())
.def_readwrite("b", &NestC::b);
m.def("get_NestC", [](const NestC &c) { return c.value; });
+
+
+ // test_overriding_eq_reset_hash
+ // #2191 Overriding __eq__ should set __hash__ to None
+ struct Comparable {
+ int value;
+ bool operator==(const Comparable& rhs) const {return value == rhs.value;}
+ };
+
+ struct Hashable : Comparable {
+ explicit Hashable(int value): Comparable{value}{};
+ size_t hash() const { return static_cast<size_t>(value); }
+ };
+
+ struct Hashable2 : Hashable {
+ using Hashable::Hashable;
+ };
+
+ py::class_<Comparable>(m, "Comparable")
+ .def(py::init<int>())
+ .def(py::self == py::self);
+
+ py::class_<Hashable>(m, "Hashable")
+ .def(py::init<int>())
+ .def(py::self == py::self)
+ .def("__hash__", &Hashable::hash);
+
+ // define __hash__ before __eq__
+ py::class_<Hashable2>(m, "Hashable2")
+ .def("__hash__", &Hashable::hash)
+ .def(py::init<int>())
+ .def(py::self == py::self);
}
#ifndef _MSC_VER
diff --git a/tests/test_operator_overloading.py b/tests/test_operator_overloading.py
index 6c92722..39e3aee 100644
--- a/tests/test_operator_overloading.py
+++ b/tests/test_operator_overloading.py
@@ -127,3 +127,19 @@
assert abase.value == 42
del abase, b
pytest.gc_collect()
+
+
+def test_overriding_eq_reset_hash():
+
+ assert m.Comparable(15) is not m.Comparable(15)
+ assert m.Comparable(15) == m.Comparable(15)
+
+ with pytest.raises(TypeError):
+ hash(m.Comparable(15)) # TypeError: unhashable type: 'm.Comparable'
+
+ for hashable in (m.Hashable, m.Hashable2):
+ assert hashable(15) is not hashable(15)
+ assert hashable(15) == hashable(15)
+
+ assert hash(hashable(15)) == 15
+ assert hash(hashable(15)) == hash(hashable(15))