Improve Self type usage accross stdlib (#7183)

stdlib/asyncio/futures.pyi

@@ -1,4 +1,5 @@
 import sys
+from _typeshed import Self
 from concurrent.futures._base import Error, Future as _ConcurrentFuture
 from typing import Any, Awaitable, Callable, Generator, Iterable, TypeVar
 
@@ -16,7 +17,6 @@ if sys.version_info >= (3, 9):
     from types import GenericAlias
 
 _T = TypeVar("_T")
-_S = TypeVar("_S")
 
 if sys.version_info < (3, 7):
     class _TracebackLogger:
@@ -39,12 +39,12 @@ class Future(Awaitable[_T], Iterable[_T]):
     def __del__(self) -> None: ...
     if sys.version_info >= (3, 7):
         def get_loop(self) -> AbstractEventLoop: ...
-        def _callbacks(self: _S) -> list[tuple[Callable[[_S], Any], Context]]: ...
-        def add_done_callback(self: _S, __fn: Callable[[_S], Any], *, context: Context | None = ...) -> None: ...
+        def _callbacks(self: Self) -> list[tuple[Callable[[Self], Any], Context]]: ...
+        def add_done_callback(self: Self, __fn: Callable[[Self], Any], *, context: Context | None = ...) -> None: ...
     else:
         @property
-        def _callbacks(self: _S) -> list[Callable[[_S], Any]]: ...
-        def add_done_callback(self: _S, __fn: Callable[[_S], Any]) -> None: ...
+        def _callbacks(self: Self) -> list[Callable[[Self], Any]]: ...
+        def add_done_callback(self: Self, __fn: Callable[[Self], Any]) -> None: ...
     if sys.version_info >= (3, 9):
         def cancel(self, msg: Any | None = ...) -> bool: ...
     else:
@@ -54,7 +54,7 @@ class Future(Awaitable[_T], Iterable[_T]):
     def done(self) -> bool: ...
     def result(self) -> _T: ...
     def exception(self) -> BaseException | None: ...
-    def remove_done_callback(self: _S, __fn: Callable[[_S], Any]) -> int: ...
+    def remove_done_callback(self: Self, __fn: Callable[[Self], Any]) -> int: ...
     def set_result(self, __result: _T) -> None: ...
     def set_exception(self, __exception: type | BaseException) -> None: ...
     def __iter__(self) -> Generator[Any, None, _T]: ...

stdlib/collections/__init__.pyi

@@ -112,8 +112,6 @@ class UserList(MutableSequence[_T]):
     def sort(self, *, key: Callable[[_T], SupportsRichComparison], reverse: bool = ...) -> None: ...
     def extend(self, other: Iterable[_T]) -> None: ...
 
-_UserStringT = TypeVar("_UserStringT", bound=UserString)
-
 class UserString(Sequence[str]):
     data: str
     def __init__(self, seq: object) -> None: ...
@@ -129,8 +127,8 @@ class UserString(Sequence[str]):
     def __len__(self) -> int: ...
     # It should return a str to implement Sequence correctly, but it doesn't.
     def __getitem__(self: Self, i: SupportsIndex | slice) -> Self: ...  # type: ignore[override]
-    def __iter__(self: _UserStringT) -> Iterator[_UserStringT]: ...  # type: ignore[override]
-    def __reversed__(self: _UserStringT) -> Iterator[_UserStringT]: ...  # type: ignore[override]
+    def __iter__(self: Self) -> Iterator[Self]: ...  # type: ignore[override]
+    def __reversed__(self: Self) -> Iterator[Self]: ...  # type: ignore[override]
     def __add__(self: Self, other: object) -> Self: ...
     def __mul__(self: Self, n: int) -> Self: ...
     def __mod__(self: Self, args: Any) -> Self: ...