Overload bool.__new/bool__ for Literal bools

stdlib/@tests/test_cases/builtins/check_bool.py

@@ -0,0 +1,20 @@
+from typing_extensions import Literal, assert_type
+
+assert_type(bool(), Literal[False])
+assert_type(bool(False), Literal[False])
+assert_type(bool(True), Literal[True])
+assert_type(bool(42), bool)
+
+
+class Truthy:
+    def __bool__(self) -> Literal[True]:
+        return True
+
+
+class Falsy:
+    def __bool__(self) -> Literal[False]:
+        return False
+
+
+assert_type(bool(Truthy()), Literal[True])
+assert_type(bool(Falsy()), Literal[False])

stdlib/builtins.pyi

@@ -966,9 +966,24 @@ class memoryview(Sequence[_I]):
     if sys.version_info >= (3, 14):
         def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
+class _Truthy(Protocol):
+    def __bool__(self) -> Literal[True]: ...
+
+class _Falsy(Protocol):
+    def __bool__(self) -> Literal[False]: ...
+
 @final
 class bool(int):
-    def __new__(cls, o: object = False, /) -> Self: ...
+    @overload
+    def __new__(cls, o: _Truthy, /) -> Literal[True]: ...
+    @overload
+    def __new__(cls, o: _Falsy = False, /) -> Literal[False]: ...
+    @overload
+    def __new__(cls, o: object, /) -> Self: ...
+    @overload
+    def __bool__(self: Literal[True]) -> Literal[True]: ...
+    @overload
+    def __bool__(self: Literal[False]) -> Literal[False]: ...
     # The following overloads could be represented more elegantly with a TypeVar("_B", bool, int),
     # however mypy has a bug regarding TypeVar constraints (https://github.com/python/mypy/issues/11880).
     @overload