add overload to tuple.__new__ to better express an empty tuple (#7454)

Co-authored-by: Alex Waygood <[email protected]>

Author: xavdid

stdlib/builtins.pyi

@@ -910,7 +910,12 @@ class slice:
     def indices(self, __len: SupportsIndex) -> tuple[int, int, int]: ...
 
 class tuple(Sequence[_T_co], Generic[_T_co]):
-    def __new__(cls: type[Self], __iterable: Iterable[_T_co] = ...) -> Self: ...
+    # overloads are ordered this way to pass `isinstance` checks
+    # see: https://github.com/python/typeshed/pull/7454#issuecomment-1061490888
+    @overload
+    def __new__(cls: type[Self], __iterable: Iterable[_T_co]) -> Self: ...
+    @overload
+    def __new__(cls) -> tuple[()]: ...
     def __len__(self) -> int: ...
     def __contains__(self, __x: object) -> bool: ...
     @overload