bpo-29894: Deprecate returning an instance of complex subclass from __complex__. (#798)
In a future versions of Python this can be an error.
diff --git a/Lib/test/test_complex.py b/Lib/test/test_complex.py
index cee4934..2d883c5 100644
--- a/Lib/test/test_complex.py
+++ b/Lib/test/test_complex.py
@@ -383,8 +383,9 @@
def __complex__(self):
return None
- self.assertAlmostEqual(complex(complex0(1j)), 42j)
- self.assertAlmostEqual(complex(complex1(1j)), 2j)
+ self.assertEqual(complex(complex0(1j)), 42j)
+ with self.assertWarns(DeprecationWarning):
+ self.assertEqual(complex(complex1(1j)), 2j)
self.assertRaises(TypeError, complex, complex2(1j))
@support.requires_IEEE_754
diff --git a/Lib/test/test_getargs2.py b/Lib/test/test_getargs2.py
index 8a194aa..e5d9aa6 100644
--- a/Lib/test/test_getargs2.py
+++ b/Lib/test/test_getargs2.py
@@ -408,7 +408,8 @@
self.assertEqual(getargs_D(ComplexSubclass(7.5+0.25j)), 7.5+0.25j)
self.assertEqual(getargs_D(ComplexSubclass2(7.5+0.25j)), 7.5+0.25j)
self.assertRaises(TypeError, getargs_D, BadComplex())
- self.assertEqual(getargs_D(BadComplex2()), 4.25+0.5j)
+ with self.assertWarns(DeprecationWarning):
+ self.assertEqual(getargs_D(BadComplex2()), 4.25+0.5j)
self.assertEqual(getargs_D(BadComplex3(7.5+0.25j)), 7.5+0.25j)
for x in (DBL_MIN, -DBL_MIN, DBL_MAX, -DBL_MAX, INF, -INF):
diff --git a/Misc/NEWS b/Misc/NEWS
index 9b0414a..a5653c8 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,10 @@
Core and Builtins
-----------------
+- bpo-29894: The deprecation warning is emitted if __complex__ returns an
+ instance of a strict subclass of complex. In a future versions of Python
+ this can be an error.
+
- bpo-29859: Show correct error messages when any of the pthread_* calls in
thread_pthread.h fails.
diff --git a/Objects/complexobject.c b/Objects/complexobject.c
index 773ddb3..5ebb504 100644
--- a/Objects/complexobject.c
+++ b/Objects/complexobject.c
@@ -274,7 +274,8 @@
}
static PyObject *
-try_complex_special_method(PyObject *op) {
+try_complex_special_method(PyObject *op)
+{
PyObject *f;
_Py_IDENTIFIER(__complex__);
@@ -282,9 +283,22 @@
if (f) {
PyObject *res = _PyObject_CallNoArg(f);
Py_DECREF(f);
- if (res != NULL && !PyComplex_Check(res)) {
- PyErr_SetString(PyExc_TypeError,
- "__complex__ should return a complex object");
+ if (!res || PyComplex_CheckExact(res)) {
+ return res;
+ }
+ if (!PyComplex_Check(res)) {
+ PyErr_Format(PyExc_TypeError,
+ "__complex__ returned non-complex (type %.200s)",
+ res->ob_type->tp_name);
+ Py_DECREF(res);
+ return NULL;
+ }
+ /* Issue #29894: warn if 'res' not of exact type complex. */
+ if (PyErr_WarnFormat(PyExc_DeprecationWarning, 1,
+ "__complex__ returned non-complex (type %.200s). "
+ "The ability to return an instance of a strict subclass of complex "
+ "is deprecated, and may be removed in a future version of Python.",
+ res->ob_type->tp_name)) {
Py_DECREF(res);
return NULL;
}
@@ -1030,12 +1044,7 @@
}
if (tmp == NULL)
return NULL;
- if (!PyFloat_Check(tmp)) {
- PyErr_SetString(PyExc_TypeError,
- "float(r) didn't return a float");
- Py_DECREF(tmp);
- return NULL;
- }
+ assert(PyFloat_Check(tmp));
cr.real = PyFloat_AsDouble(tmp);
cr.imag = 0.0;
Py_DECREF(tmp);