Refine the copy._SupportsReplace.__replace__ signature

stdlib/@tests/test_cases/check_copy.py

@@ -2,6 +2,7 @@
 
 import copy
 import sys
+from typing import Any, Generic, TypeVar
 from typing_extensions import Self, assert_type
 
 
@@ -19,3 +20,20 @@ def __replace__(self, val: int) -> Self:
     obj = ReplaceableClass(42)
     cpy = copy.replace(obj, val=23)
     assert_type(cpy, ReplaceableClass)
+
+
+_T_co = TypeVar("_T_co", covariant=True)
+
+
+class Box(Generic[_T_co]):
+    def __init__(self, value: _T_co, /) -> None:
+        self.value = value
+
+    def __replace__(self, value: Any) -> Box[Any]:
+        return Box(value)
+
+
+if sys.version_info >= (3, 13):
+    box1: Box[int] = Box(42)
+    box2 = copy.replace(box1, val="spam")
+    assert_type(box2, Box[Any])

stdlib/copy.pyi

@@ -1,16 +1,17 @@
 import sys
 from typing import Any, Protocol, TypeVar, type_check_only
-from typing_extensions import Self
+from typing_extensions import ParamSpec
 
 __all__ = ["Error", "copy", "deepcopy"]
 
 _T = TypeVar("_T")
-_SR = TypeVar("_SR", bound=_SupportsReplace)
+_Tss = ParamSpec("_Tss")
+_RT_co = TypeVar("_RT_co", covariant=True)
 
 @type_check_only
-class _SupportsReplace(Protocol):
+class _SupportsReplace(Protocol[_Tss, _RT_co]):
     # In reality doesn't support args, but there's no other great way to express this.
-    def __replace__(self, *args: Any, **kwargs: Any) -> Self: ...
+    def __replace__(self, /, *_: _Tss.args, **changes: _Tss.kwargs) -> _RT_co: ...
 
 # None in CPython but non-None in Jython
 PyStringMap: Any
@@ -21,7 +22,7 @@ def copy(x: _T) -> _T: ...
 
 if sys.version_info >= (3, 13):
     __all__ += ["replace"]
-    def replace(obj: _SR, /, **changes: Any) -> _SR: ...
+    def replace(obj: _SupportsReplace[..., _RT_co], /, **changes: Any) -> _RT_co: ...
 
 class Error(Exception): ...