ctypes.POINTER(None) returns ctypes.c_void_p

[junkmd]

Fixes #12736.

[Avasam]

As per the discussion in the the issue, it might be worth adding some tests (in stdlib/@tests/test_cases/check_ctypes.py ?) to show the expected return type as per common usage. If you are correct, then the return type isn't obvious. If not, then it'll show though isinstance/assert_type checks. It would be a good place to eternalize your reasoning and insight in a comment too !

Other than that, I think that the overload to allow None is welcome.

[junkmd]

@Avasam

I read your comment and https://github.com/python/typeshed/blob/main/tests/REGRESSION.md.

I have committed what I thought should be added to stdlib/@tests/test_cases/check_ctypes.py, so could you check if my understanding is correct?

And it seems there's already stdlib/@tests/test_cases/multiprocessing/check_ctypes.py, and the name check_ctypes.py is duplicated, causing an error.
Could you also advise on how to resolve this?

[Avasam]

Could you also advise on how to resolve this?

Oh that's an easy fix. Just gotta make sure the filename is different. You could rename your test ctypes/check_pointer.py (imo the one in multiprocessing should be renamed, but let's avoid touching it in your PR).

[github-actions]

Diff from mypy_primer, showing the effect of this PR on open source code:

comtypes (https://github.com/enthought/comtypes)
- comtypes/typeinfo.py:511: error: Argument 1 to "POINTER" has incompatible type Module; expected "type[Never]"  [arg-type]
+ comtypes/typeinfo.py:511: error: No overload variant of "POINTER" matches argument type Module  [call-overload]
+ comtypes/typeinfo.py:511: note: Possible overload variants:
+ comtypes/typeinfo.py:511: note:     def POINTER(None, /) -> type[c_void_p]
+ comtypes/typeinfo.py:511: note:     def [_CT: _CData] POINTER(type[_CT], /) -> type[_Pointer[_CT]]
- comtypes/typeinfo.py:830: error: Argument 1 to "POINTER" has incompatible type Module; expected "type[Any]"  [arg-type]
- comtypes/typeinfo.py:842: error: Argument 1 to "POINTER" has incompatible type Module; expected "type[Any]"  [arg-type]
- comtypes/typeinfo.py:868: error: Argument 1 to "POINTER" has incompatible type Module; expected "type[Never]"  [arg-type]
- comtypes/typeinfo.py:1036: error: Argument 1 to "POINTER" has incompatible type Module; expected "type[Any]"  [arg-type]
+ comtypes/typeinfo.py:830: error: No overload variant of "POINTER" matches argument type Module  [call-overload]
+ comtypes/typeinfo.py:830: note: Possible overload variants:
+ comtypes/typeinfo.py:830: note:     def POINTER(None, /) -> type[c_void_p]
+ comtypes/typeinfo.py:830: note:     def [_CT: _CData] POINTER(type[_CT], /) -> type[_Pointer[_CT]]
+ comtypes/typeinfo.py:842: error: No overload variant of "POINTER" matches argument type Module  [call-overload]
+ comtypes/typeinfo.py:842: note: Possible overload variants:
+ comtypes/typeinfo.py:842: note:     def POINTER(None, /) -> type[c_void_p]
+ comtypes/typeinfo.py:842: note:     def [_CT: _CData] POINTER(type[_CT], /) -> type[_Pointer[_CT]]
+ comtypes/typeinfo.py:868: error: No overload variant of "POINTER" matches argument type Module  [call-overload]
+ comtypes/typeinfo.py:868: note: Possible overload variants:
+ comtypes/typeinfo.py:868: note:     def POINTER(None, /) -> type[c_void_p]
+ comtypes/typeinfo.py:868: note:     def [_CT: _CData] POINTER(type[_CT], /) -> type[_Pointer[_CT]]
+ comtypes/typeinfo.py:1036: error: No overload variant of "POINTER" matches argument type Module  [call-overload]
+ comtypes/typeinfo.py:1036: note: Possible overload variants:
+ comtypes/typeinfo.py:1036: note:     def POINTER(None, /) -> type[c_void_p]
+ comtypes/typeinfo.py:1036: note:     def [_CT: _CData] POINTER(type[_CT], /) -> type[_Pointer[_CT]]
- comtypes/typeinfo.py:1102: error: Argument 1 to "POINTER" has incompatible type Module; expected "type[Never]"  [arg-type]
+ comtypes/typeinfo.py:1102: error: No overload variant of "POINTER" matches argument type Module  [call-overload]
+ comtypes/typeinfo.py:1102: note: Possible overload variants:
+ comtypes/typeinfo.py:1102: note:     def POINTER(None, /) -> type[c_void_p]
+ comtypes/typeinfo.py:1102: note:     def [_CT: _CData] POINTER(type[_CT], /) -> type[_Pointer[_CT]]
+ comtypes/safearray.py:70: error: Unused "type: ignore" comment  [unused-ignore]
- comtypes/errorinfo.py:13: error: Argument 1 to "POINTER" has incompatible type Module; expected "type[Never]"  [arg-type]
+ comtypes/errorinfo.py:13: error: No overload variant of "POINTER" matches argument type Module  [call-overload]
+ comtypes/errorinfo.py:13: note: Possible overload variants:
+ comtypes/errorinfo.py:13: note:     def POINTER(None, /) -> type[c_void_p]
+ comtypes/errorinfo.py:13: note:     def [_CT: _CData] POINTER(type[_CT], /) -> type[_Pointer[_CT]]
- comtypes/errorinfo.py:24: error: Argument 1 to "POINTER" has incompatible type Module; expected "type[Never]"  [arg-type]
+ comtypes/errorinfo.py:24: error: No overload variant of "POINTER" matches argument type Module  [call-overload]
+ comtypes/errorinfo.py:24: note: Possible overload variants:
+ comtypes/errorinfo.py:24: note:     def POINTER(None, /) -> type[c_void_p]
+ comtypes/errorinfo.py:24: note:     def [_CT: _CData] POINTER(type[_CT], /) -> type[_Pointer[_CT]]
- comtypes/errorinfo.py:42: error: Argument 1 to "POINTER" has incompatible type Module; expected "type[Never]"  [arg-type]
+ comtypes/errorinfo.py:42: error: No overload variant of "POINTER" matches argument type Module  [call-overload]
+ comtypes/errorinfo.py:42: note: Possible overload variants:
+ comtypes/errorinfo.py:42: note:     def POINTER(None, /) -> type[c_void_p]
+ comtypes/errorinfo.py:42: note:     def [_CT: _CData] POINTER(type[_CT], /) -> type[_Pointer[_CT]]
- comtypes/_post_coinit/unknwn.py:521: error: Argument 1 to "POINTER" has incompatible type Module; expected "type[Any]"  [arg-type]
+ comtypes/_post_coinit/unknwn.py:521: error: No overload variant of "POINTER" matches argument type Module  [call-overload]
+ comtypes/_post_coinit/unknwn.py:521: note: Possible overload variants:
+ comtypes/_post_coinit/unknwn.py:521: note:     def POINTER(None, /) -> type[c_void_p]
+ comtypes/_post_coinit/unknwn.py:521: note:     def [_CT: _CData] POINTER(type[_CT], /) -> type[_Pointer[_CT]]
- comtypes/_post_coinit/misc.py:51: error: Argument 1 to "POINTER" has incompatible type Module; expected "type[Never]"  [arg-type]
+ comtypes/_post_coinit/misc.py:51: error: No overload variant of "POINTER" matches argument type Module  [call-overload]
+ comtypes/_post_coinit/misc.py:51: note: Possible overload variants:
+ comtypes/_post_coinit/misc.py:51: note:     def POINTER(None, /) -> type[c_void_p]
+ comtypes/_post_coinit/misc.py:51: note:     def [_CT: _CData] POINTER(type[_CT], /) -> type[_Pointer[_CT]]
- comtypes/_post_coinit/misc.py:80: error: Argument 1 to "POINTER" has incompatible type Module; expected "type[Never]"  [arg-type]
- comtypes/_post_coinit/misc.py:81: error: Argument 1 to "POINTER" has incompatible type Module; expected "type[Never]"  [arg-type]
+ comtypes/_post_coinit/misc.py:80: error: No overload variant of "POINTER" matches argument type Module  [call-overload]
+ comtypes/_post_coinit/misc.py:80: note: Possible overload variants:
+ comtypes/_post_coinit/misc.py:80: note:     def POINTER(None, /) -> type[c_void_p]
+ comtypes/_post_coinit/misc.py:80: note:     def [_CT: _CData] POINTER(type[_CT], /) -> type[_Pointer[_CT]]
+ comtypes/_post_coinit/misc.py:81: error: No overload variant of "POINTER" matches argument type Module  [call-overload]
+ comtypes/_post_coinit/misc.py:81: note: Possible overload variants:
+ comtypes/_post_coinit/misc.py:81: note:     def POINTER(None, /) -> type[c_void_p]
+ comtypes/_post_coinit/misc.py:81: note:     def [_CT: _CData] POINTER(type[_CT], /) -> type[_Pointer[_CT]]
- comtypes/_post_coinit/misc.py:188: error: Argument 1 to "POINTER" has incompatible type Module; expected "type[Never]"  [arg-type]
+ comtypes/_post_coinit/misc.py:188: error: No overload variant of "POINTER" matches argument type Module  [call-overload]
+ comtypes/_post_coinit/misc.py:188: note: Possible overload variants:
+ comtypes/_post_coinit/misc.py:188: note:     def POINTER(None, /) -> type[c_void_p]
+ comtypes/_post_coinit/misc.py:188: note:     def [_CT: _CData] POINTER(type[_CT], /) -> type[_Pointer[_CT]]
- comtypes/_post_coinit/misc.py:242: error: Argument 1 to "POINTER" has incompatible type Module; expected "type[Any]"  [arg-type]
- comtypes/_post_coinit/misc.py:245: error: Argument 1 to "POINTER" has incompatible type Module; expected "type[Any]"  [arg-type]
+ comtypes/_post_coinit/misc.py:242: error: No overload variant of "POINTER" matches argument type Module  [call-overload]
+ comtypes/_post_coinit/misc.py:242: note: Possible overload variants:
+ comtypes/_post_coinit/misc.py:242: note:     def POINTER(None, /) -> type[c_void_p]
+ comtypes/_post_coinit/misc.py:242: note:     def [_CT: _CData] POINTER(type[_CT], /) -> type[_Pointer[_CT]]
+ comtypes/_post_coinit/misc.py:245: error: No overload variant of "POINTER" matches argument type Module  [call-overload]
+ comtypes/_post_coinit/misc.py:245: note: Possible overload variants:
+ comtypes/_post_coinit/misc.py:245: note:     def POINTER(None, /) -> type[c_void_p]
+ comtypes/_post_coinit/misc.py:245: note:     def [_CT: _CData] POINTER(type[_CT], /) -> type[_Pointer[_CT]]

[srittau]

The primer output is just changed error messages.

[junkmd]

@Avasam

Oh that's an easy fix. Just gotta make sure the filename is different. You could rename your test ctypes/check_pointer.py

After following your advice and using git mv, the error no longer occurred.
Thank you.

(imo the one in multiprocessing should be renamed, but let's avoid touching it in your PR).

No objection.