The result of TextIOWrapper.detach() should be IO[bytes]

[serhiy-storchaka]

For the following example:

import sys, io

if isinstance(sys.stdout, io.TextIOWrapper) and sys.version_info < (3, 7):
    sys.stdout = io.TextIOWrapper(
        sys.stdout.detach(),
        encoding="ascii",
        errors="replace")

I get the following error:

reconfigure36.py:5: error: Argument 1 to "TextIOWrapper" has incompatible type "IOBase"; expected "IO[bytes]"

Should not TextIOWrapper.detach() return IO[bytes] instead of IOBase?

Replacing sys.stdout.detach() with sys.stdout.buffer fixes the complains.

[srittau]

IO types predate protocols and are a mess. detach() should ideally return whatever it returns in the implementation (I assume this is the first argument passed to its constructor?) and TextIOWrapper should ideally expect a custom protocol and things should work. That said, your suggestion would most likely work fine for now. PR welcome!