Issue #24731: Fixed crash on converting objects with special methods

__str__, __trunc__, and __float__ returning instances of subclasses of
str, long, and float to subclasses of str, long, and float correspondingly.

1 files changed, 15 insertions, 0 deletions

diff --git a/Lib/test/test_float.py b/Lib/test/test_float.py
index 4224306..4ec894c 100644
--- a/Lib/test/test_float.py
+++ b/Lib/test/test_float.py
@@ -27,6 +27,12 @@ requires_IEEE_754 = unittest.skipUnless(have_getformat and
 test_dir = os.path.dirname(__file__) or os.curdir
 format_testfile = os.path.join(test_dir, 'formatfloat_testcases.txt')
 
+class FloatSubclass(float):
+    pass
+
+class OtherFloatSubclass(float):
+    pass
+
 class GeneralFloatCases(unittest.TestCase):
 
     def test_float(self):
@@ -200,6 +206,15 @@ class GeneralFloatCases(unittest.TestCase):
                 return ""
         self.assertRaises(TypeError, time.sleep, Foo5())
 
+        # Issue #24731
+        class F:
+            def __float__(self):
+                return OtherFloatSubclass(42.)
+        self.assertAlmostEqual(float(F()), 42.)
+        self.assertIs(type(float(F())), OtherFloatSubclass)
+        self.assertAlmostEqual(FloatSubclass(F()), 42.)
+        self.assertIs(type(FloatSubclass(F())), FloatSubclass)
+
     def test_is_integer(self):
         self.assertFalse((1.1).is_integer())
         self.assertTrue((1.).is_integer())