From 9052674aa8f059ac68f8726005751ebb53a271ce Mon Sep 17 00:00:00 2001
From: Kyle Altendorf <sda@fstab.net>
Date: Mon, 25 Oct 2021 19:28:33 -0400
Subject: [PATCH] bytes.fromhex() returns cls instance, not bytes (#6201)

```console
$ cat y.py
import typing

class MyBytes(bytes):
    pass


x = MyBytes.fromhex("abcd")
if typing.TYPE_CHECKING:
    reveal_type(x)
else:
    print(x.__class__.__name__)
```

```console
$ for v in 3.6 3.7 3.8 3.9 3.10; do echo -n "$v: " ; python$v y.py; done
3.6: MyBytes
3.7: MyBytes
3.8: MyBytes
3.9: MyBytes
3.10: MyBytes
```

```console
$ venv/bin/mypy y.py
y.py:9: note: Revealed type is "builtins.bytes"
```
---
 stdlib/builtins.pyi | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/stdlib/builtins.pyi b/stdlib/builtins.pyi
index 225388cc9..4694042ca 100644
--- a/stdlib/builtins.pyi
+++ b/stdlib/builtins.pyi
@@ -493,7 +493,7 @@ class bytes(ByteString):
     def upper(self) -> bytes: ...
     def zfill(self, __width: SupportsIndex) -> bytes: ...
     @classmethod
-    def fromhex(cls, __s: str) -> bytes: ...
+    def fromhex(cls: Type[_T], __s: str) -> _T: ...
     @staticmethod
     def maketrans(__frm: bytes, __to: bytes) -> bytes: ...
     def __len__(self) -> int: ...