1 files changed, 59 insertions, 22 deletions
diff --git a/Lib/test/test_bytes.py b/Lib/test/test_bytes.py
index afd506f..a3804a9 100644
--- a/Lib/test/test_bytes.py
+++ b/Lib/test/test_bytes.py
@@ -46,6 +46,10 @@ class Indexable:
 
 class BaseBytesTest:
 
+    def assertTypedEqual(self, actual, expected):
+        self.assertIs(type(actual), type(expected))
+        self.assertEqual(actual, expected)
+
     def test_basics(self):
         b = self.type2test()
         self.assertEqual(type(b), self.type2test)
@@ -1023,36 +1027,63 @@ class BytesTest(BaseBytesTest, unittest.TestCase):
             self.assertRaises(TypeError, f.readinto, b"")
 
     def test_custom(self):
-        class A:
-            def __bytes__(self):
-                return b'abc'
-        self.assertEqual(bytes(A()), b'abc')
-        class A: pass
-        self.assertRaises(TypeError, bytes, A())
-        class A:
-            def __bytes__(self):
-                return None
-        self.assertRaises(TypeError, bytes, A())
-        class A:
+        self.assertEqual(bytes(BytesSubclass(b'abc')), b'abc')
+        self.assertEqual(BytesSubclass(OtherBytesSubclass(b'abc')),
+                         BytesSubclass(b'abc'))
+        self.assertEqual(bytes(WithBytes(b'abc')), b'abc')
+        self.assertEqual(BytesSubclass(WithBytes(b'abc')), BytesSubclass(b'abc'))
+
+        class NoBytes: pass
+        self.assertRaises(TypeError, bytes, NoBytes())
+        self.assertRaises(TypeError, bytes, WithBytes('abc'))
+        self.assertRaises(TypeError, bytes, WithBytes(None))
+        class IndexWithBytes:
             def __bytes__(self):
                 return b'a'
             def __index__(self):
                 return 42
-        self.assertEqual(bytes(A()), b'a')
+        self.assertEqual(bytes(IndexWithBytes()), b'a')
         # Issue #25766
-        class A(str):
+        class StrWithBytes(str):
+            def __new__(cls, value):
+                self = str.__new__(cls, '\u20ac')
+                self.value = value
+                return self
             def __bytes__(self):
-                return b'abc'
-        self.assertEqual(bytes(A('\u20ac')), b'abc')
-        self.assertEqual(bytes(A('\u20ac'), 'iso8859-15'), b'\xa4')
+                return self.value
+        self.assertEqual(bytes(StrWithBytes(b'abc')), b'abc')
+        self.assertEqual(bytes(StrWithBytes(b'abc'), 'iso8859-15'), b'\xa4')
+        self.assertEqual(bytes(StrWithBytes(BytesSubclass(b'abc'))), b'abc')
+        self.assertEqual(BytesSubclass(StrWithBytes(b'abc')), BytesSubclass(b'abc'))
+        self.assertEqual(BytesSubclass(StrWithBytes(b'abc'), 'iso8859-15'),
+                         BytesSubclass(b'\xa4'))
+        self.assertEqual(BytesSubclass(StrWithBytes(BytesSubclass(b'abc'))),
+                         BytesSubclass(b'abc'))
+        self.assertEqual(BytesSubclass(StrWithBytes(OtherBytesSubclass(b'abc'))),
+                         BytesSubclass(b'abc'))
         # Issue #24731
-        class A:
+        self.assertTypedEqual(bytes(WithBytes(BytesSubclass(b'abc'))), BytesSubclass(b'abc'))
+        self.assertTypedEqual(BytesSubclass(WithBytes(BytesSubclass(b'abc'))),
+                              BytesSubclass(b'abc'))
+        self.assertTypedEqual(BytesSubclass(WithBytes(OtherBytesSubclass(b'abc'))),
+                              BytesSubclass(b'abc'))
+
+        class BytesWithBytes(bytes):
+            def __new__(cls, value):
+                self = bytes.__new__(cls, b'\xa4')
+                self.value = value
+                return self
             def __bytes__(self):
-                return OtherBytesSubclass(b'abc')
-        self.assertEqual(bytes(A()), b'abc')
-        self.assertIs(type(bytes(A())), OtherBytesSubclass)
-        self.assertEqual(BytesSubclass(A()), b'abc')
-        self.assertIs(type(BytesSubclass(A())), BytesSubclass)
+                return self.value
+        self.assertTypedEqual(bytes(BytesWithBytes(b'abc')), b'abc')
+        self.assertTypedEqual(BytesSubclass(BytesWithBytes(b'abc')),
+                              BytesSubclass(b'abc'))
+        self.assertTypedEqual(bytes(BytesWithBytes(BytesSubclass(b'abc'))),
+                              BytesSubclass(b'abc'))
+        self.assertTypedEqual(BytesSubclass(BytesWithBytes(BytesSubclass(b'abc'))),
+                              BytesSubclass(b'abc'))
+        self.assertTypedEqual(BytesSubclass(BytesWithBytes(OtherBytesSubclass(b'abc'))),
+                              BytesSubclass(b'abc'))
 
     # Test PyBytes_FromFormat()
     def test_from_format(self):
@@ -2069,6 +2100,12 @@ class BytesSubclass(bytes):
 class OtherBytesSubclass(bytes):
     pass
 
+class WithBytes:
+    def __init__(self, value):
+        self.value = value
+    def __bytes__(self):
+        return self.value
+
 class ByteArraySubclassTest(SubclassTest, unittest.TestCase):
     basetype = bytearray
     type2test = ByteArraySubclass