Use conditional overloads to simplify several stdlib functions (#7540)

stdlib/builtins.pyi

@@ -1477,16 +1477,14 @@ def sorted(
 ) -> list[SupportsRichComparisonT]: ...
 @overload
 def sorted(__iterable: Iterable[_T], *, key: Callable[[_T], SupportsRichComparison], reverse: bool = ...) -> list[_T]: ...
+@overload
+def sum(__iterable: Iterable[_T]) -> _T | Literal[0]: ...
 
 if sys.version_info >= (3, 8):
-    @overload
-    def sum(__iterable: Iterable[_T]) -> _T | Literal[0]: ...
     @overload
     def sum(__iterable: Iterable[_T], start: _S) -> _T | _S: ...
 
 else:
-    @overload
-    def sum(__iterable: Iterable[_T]) -> _T | Literal[0]: ...
     @overload
     def sum(__iterable: Iterable[_T], __start: _S) -> _T | _S: ...
 

stdlib/dataclasses.pyi

@@ -65,11 +65,20 @@ def astuple(obj: Any) -> tuple[Any, ...]: ...
 @overload
 def astuple(obj: Any, *, tuple_factory: Callable[[list[Any]], _T]) -> _T: ...
 
-if sys.version_info >= (3, 10):
+if sys.version_info >= (3, 8):
+    # cls argument is now positional-only
     @overload
     def dataclass(__cls: type[_T]) -> type[_T]: ...
     @overload
     def dataclass(__cls: None) -> Callable[[type[_T]], type[_T]]: ...
+
+else:
+    @overload
+    def dataclass(_cls: type[_T]) -> type[_T]: ...
+    @overload
+    def dataclass(_cls: None) -> Callable[[type[_T]], type[_T]]: ...
+
+if sys.version_info >= (3, 10):
     @overload
     def dataclass(
         *,
@@ -84,22 +93,7 @@ if sys.version_info >= (3, 10):
         slots: bool = ...,
     ) -> Callable[[type[_T]], type[_T]]: ...
 
-elif sys.version_info >= (3, 8):
-    # cls argument is now positional-only
-    @overload
-    def dataclass(__cls: type[_T]) -> type[_T]: ...
-    @overload
-    def dataclass(__cls: None) -> Callable[[type[_T]], type[_T]]: ...
-    @overload
-    def dataclass(
-        *, init: bool = ..., repr: bool = ..., eq: bool = ..., order: bool = ..., unsafe_hash: bool = ..., frozen: bool = ...
-    ) -> Callable[[type[_T]], type[_T]]: ...
-
 else:
-    @overload
-    def dataclass(_cls: type[_T]) -> type[_T]: ...
-    @overload
-    def dataclass(_cls: None) -> Callable[[type[_T]], type[_T]]: ...
     @overload
     def dataclass(
         *, init: bool = ..., repr: bool = ..., eq: bool = ..., order: bool = ..., unsafe_hash: bool = ..., frozen: bool = ...

stdlib/enum.pyi

@@ -95,11 +95,11 @@ class EnumMeta(ABCMeta):
     def __members__(self: type[_EnumMemberT]) -> types.MappingProxyType[str, _EnumMemberT]: ...
     def __len__(self) -> int: ...
     def __bool__(self) -> Literal[True]: ...
+    # Simple value lookup
+    @overload  # type: ignore[override]
+    def __call__(cls: type[_EnumMemberT], value: Any, names: None = ...) -> _EnumMemberT: ...
+    # Functional Enum API
     if sys.version_info >= (3, 11):
-        # Simple value lookup
-        @overload  # type: ignore[override]
-        def __call__(cls: type[_EnumMemberT], value: Any, names: None = ...) -> _EnumMemberT: ...
-        # Functional Enum API
         @overload
         def __call__(
             cls,
@@ -113,8 +113,6 @@ class EnumMeta(ABCMeta):
             boundary: FlagBoundary | None = ...,
         ) -> type[Enum]: ...
     else:
-        @overload  # type: ignore[override]
-        def __call__(cls: type[_EnumMemberT], value: Any, names: None = ...) -> _EnumMemberT: ...
         @overload
         def __call__(
             cls,

stdlib/os/__init__.pyi

@@ -732,20 +732,15 @@ class _ScandirIterator(Iterator[DirEntry[AnyStr]], AbstractContextManager[_Scand
     def __exit__(self, *args: object) -> None: ...
     def close(self) -> None: ...
 
+@overload
+def scandir(path: None = ...) -> _ScandirIterator[str]: ...
+
 if sys.version_info >= (3, 7):
-    @overload
-    def scandir(path: None = ...) -> _ScandirIterator[str]: ...
     @overload
     def scandir(path: int) -> _ScandirIterator[str]: ...
-    @overload
-    def scandir(path: AnyStr | PathLike[AnyStr]) -> _ScandirIterator[AnyStr]: ...
-
-else:
-    @overload
-    def scandir(path: None = ...) -> _ScandirIterator[str]: ...
-    @overload
-    def scandir(path: AnyStr | PathLike[AnyStr]) -> _ScandirIterator[AnyStr]: ...
 
+@overload
+def scandir(path: AnyStr | PathLike[AnyStr]) -> _ScandirIterator[AnyStr]: ...
 def stat(path: _FdOrAnyPath, *, dir_fd: int | None = ..., follow_symlinks: bool = ...) -> stat_result: ...
 
 if sys.version_info < (3, 7):