`list.sort()` fails to detect type issue

[alexprengere]

This code is not failing under mypy:

[2, None].sort()

Interestingly, it fails on ty:

error[invalid-argument-type]: Argument to bound method `list.sort` is incorrect
 --> toto.py:1:1
  |
1 | [None, 2].sort()
  | ^^^^^^^^^^^^^^^^ Argument type `None | int` does not satisfy upper bound `SupportsDunderLT[Any] | SupportsDunderGT[Any]` of type variable `SupportsRichComparisonT`
  |
info: Type variable defined here
   --> stdlib/_typeshed/__init__.pyi:107:1
    |
107 | SupportsRichComparisonT = TypeVar("SupportsRichComparisonT", bound=SupportsRichComparison)  # noqa: Y001
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |

Found 1 diagnostic

[A5rocks]

Interestingly, mypy does infer list[int | None]. The issue, I suppose, might be that we're not checking self-types for overloads? But I find that unlikely.

[muhamedfazalps]

I would like to work on this bug. The issue is that list.sort() has overloaded signatures and mypy is not checking the self-type constraint when the list type is inferred as list[int | None]. Looking into the overload resolution code in mypy now.