Add slicing notation to F expressions

django-stubs/db/models/expressions.pyi

@@ -132,6 +132,7 @@ class F(_Deconstructible, Combinable):
     name: str
     allowed_default: ClassVar[bool]
     def __init__(self, name: str) -> None: ...
+    def __getitem__(self, subscript: int | slice) -> Sliced: ...
     def resolve_expression(
         self,
         query: Any | None = None,
@@ -154,7 +155,10 @@ class F(_Deconstructible, Combinable):
         nulls_first: bool | None = ...,
         nulls_last: bool | None = ...,
     ) -> OrderBy: ...
-    def copy(self) -> F: ...
+    def copy(self) -> Self: ...
+
+class Sliced(F):
+    def __init__(self, obj: F, subscript: int | slice) -> None: ...
 
 class ResolvedOuterRef(F):
     contains_aggregate: ClassVar[bool]

django-stubs/db/models/fields/__init__.pyi

@@ -10,7 +10,7 @@ from django.core import validators  # due to weird mypy.stubtest error
 from django.core.checks import CheckMessage
 from django.db.backends.base.base import BaseDatabaseWrapper
 from django.db.models import Model
-from django.db.models.expressions import Col, Combinable, Expression
+from django.db.models.expressions import Col, Combinable, Expression, Func
 from django.db.models.fields.reverse_related import ForeignObjectRel
 from django.db.models.query_utils import Q, RegisterLookupMixin
 from django.forms import Widget
@@ -234,6 +234,7 @@ class Field(RegisterLookupMixin, Generic[_ST, _GT]):
     def get_attname(self) -> str: ...
     def get_attname_column(self) -> tuple[str, str]: ...
     def value_to_string(self, obj: Model) -> str: ...
+    def slice_expression(self, expression: Expression, start: int, end: int | None) -> Func: ...
 
 class IntegerField(Field[_ST, _GT]):
     _pyi_private_set_type: float | int | str | Combinable