Add special case for integers raised to a power of 2 (#4473)

Author: jakebailey

stdlib/2/__builtin__.pyi

@@ -220,6 +220,9 @@ class int:
     def __rtruediv__(self, x: int) -> float: ...
     def __rmod__(self, x: int) -> int: ...
     def __rdivmod__(self, x: int) -> Tuple[int, int]: ...
+    @overload
+    def __pow__(self, __x: Literal[2], __modulo: Optional[int] = ...) -> int: ...
+    @overload
     def __pow__(self, __x: int, __modulo: Optional[int] = ...) -> Any: ...  # Return type can be int or float, depending on x.
     def __rpow__(self, x: int, mod: Optional[int] = ...) -> Any: ...
     def __and__(self, n: int) -> int: ...

stdlib/2and3/builtins.pyi

@@ -220,6 +220,9 @@ class int:
     def __rtruediv__(self, x: int) -> float: ...
     def __rmod__(self, x: int) -> int: ...
     def __rdivmod__(self, x: int) -> Tuple[int, int]: ...
+    @overload
+    def __pow__(self, __x: Literal[2], __modulo: Optional[int] = ...) -> int: ...
+    @overload
     def __pow__(self, __x: int, __modulo: Optional[int] = ...) -> Any: ...  # Return type can be int or float, depending on x.
     def __rpow__(self, x: int, mod: Optional[int] = ...) -> Any: ...
     def __and__(self, n: int) -> int: ...