ruff

03fe5601 - [ty] Substitute for `typing.Self` when checking protocol members (#21569)

[ty] Substitute for `typing.Self` when checking protocol members (#21569) This patch updates our protocol assignability checks to substitute for any occurrences of `typing.Self` in method signatures, replacing it with the class being checked for assignability against the protocol. This requires a new helper method on signatures, `apply_self`, which substitutes occurrences of `typing.Self` _without_ binding the `self` parameter. We also update the `try_upcast_to_callable` method. Before, it would return a `Type`, since certain types upcast to a _union_ of callables, not to a single callable. However, even in that case, we know that every element of the union is a callable. We now return a vector of `CallableType`. (Actually a smallvec to handle the most common case of a single callable; and wrapped in a new type so that we can provide helper methods.) If there is more than one element in the result, it represents a union of callables. This lets callers get at the `CallableType` instances in a more type-safe way. (This makes it easier for our protocol checking code to call the new `apply_self` helper.) We also provide an `into_type` method so that callers that really do want a `Type` can get the original result easily. --------- Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>