Fix type.__mro__ resolving to property

[crypt0lith]

type.__mro__ resolves to property instead of tuple[type, ...]. type is in its own MRO, so attribute access resolves to the unbound getter instead of the actual attribute.

Replace the __mro__ property with __mro__: Final[tuple[type, ...]] to keep the attribute read-only without relying on the descriptor protocol, matching type.__dict__:

typeshed/stdlib/builtins.pyi

Line 192 in 0e69087

__dict__: Final[types.MappingProxyType[str, Any]] # type: ignore[assignment]

Minimal repro

reveal_type(type.__mro__)
reveal_type((*type.__mro__,))

pyright 1.1.414 gives the following error:

1:13 - information: Type of "type.__mro__" is "property"
2:13 - information: Type of "(*type.__mro__, )" is "tuple[Unknown, ...]"
2:14 - error: "property" is not iterable
  "__iter__" method not defined (reportGeneralTypeIssues)

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉