Use an abstract QuerySet-like collection type

django-stubs/forms/models.pyi

@@ -15,7 +15,7 @@ from django.forms.renderers import BaseRenderer
 from django.forms.utils import ErrorList, _DataT, _FilesT
 from django.forms.widgets import Widget
 from django.utils.choices import BaseChoiceIterator, CallableChoiceIterator, _Choices, _ChoicesCallable
-from django.utils.datastructures import _PropertyDescriptor
+from django.utils.datastructures import _PropertyDescriptor, _QuerySetLike
 from django.utils.functional import _StrOrPromise
 from typing_extensions import TypeAlias
 
@@ -126,7 +126,7 @@ class BaseModelFormSet(Generic[_M, _ModelFormT], BaseFormSet[_ModelFormT]):
         **kwargs: Any,
     ) -> None: ...
     def initial_form_count(self) -> int: ...
-    def get_queryset(self) -> QuerySet[_M]: ...
+    def get_queryset(self) -> _QuerySetLike[_M]: ...
     def save_new(self, form: _ModelFormT, commit: bool = ...) -> _M: ...
     def save_existing(self, form: _ModelFormT, obj: _M, commit: bool = ...) -> _M: ...
     def delete_existing(self, obj: _M, commit: bool = ...) -> None: ...

django-stubs/utils/datastructures.pyi

@@ -1,4 +1,4 @@
-from collections.abc import Collection, Iterable, Iterator, Mapping, MutableMapping, MutableSet
+from collections.abc import Collection, Iterable, Iterator, Mapping, MutableMapping, MutableSet, Sized
 from typing import Any, Generic, NoReturn, Protocol, TypeVar, overload, type_check_only
 
 from _typeshed import Incomplete
@@ -43,6 +43,17 @@ class _IndexableCollection(Protocol[_I], Collection[_I]):  # noqa: PYI046
     @overload
     def __getitem__(self, index: slice) -> Self: ...
 
+@type_check_only
+class _QuerySetLike(Protocol[_I], Iterable[_I], Sized):  # noqa: PYI046
+    """
+    Abstract collection type reflecting methods provided by QuerySet.
+    """
+
+    @overload
+    def __getitem__(self, index: int) -> _I: ...
+    @overload
+    def __getitem__(self, index: slice) -> Self: ...
+
 class OrderedSet(MutableSet[_K]):
     dict: dict[_K, None]
     def __init__(self, iterable: Iterable[_K] | None = ...) -> None: ...

tests/typecheck/test_formsets.yml

@@ -7,7 +7,7 @@
     ArticleFS(instance=Article())  # E: Argument "instance" to "BaseInlineFormSet" has incompatible type "Article"; expected "Optional[Category]"  [arg-type]
     fs = ArticleFS(instance=Category())
     reveal_type(fs.instance)  # N: Revealed type is "myapp.models.Category"
-    reveal_type(fs.get_queryset())  # N: Revealed type is "django.db.models.query.QuerySet[myapp.models.Article, myapp.models.Article]"
+    reveal_type(fs.get_queryset())  # N: Revealed type is "django.utils.datastructures._QuerySetLike[myapp.models.Article]"
   installed_apps:
     - myapp
   files: