fix handling of explicit objects annotation (#2241)

* fix handling of explicit `objects` annotation

* adjust test

mypy_django_plugin/transformers/querysets.py

@@ -33,10 +33,14 @@ def determine_proper_manager_type(ctx: FunctionContext) -> MypyType:
     assert isinstance(default_return_type, Instance)
 
     outer_model_info = helpers.get_typechecker_api(ctx).scope.active_class()
-    if outer_model_info is None or not outer_model_info.has_base(fullnames.MODEL_CLASS_FULLNAME):
+    if (
+        outer_model_info is None
+        or not outer_model_info.has_base(fullnames.MODEL_CLASS_FULLNAME)
+        or outer_model_info.self_type is None
+    ):
         return default_return_type
 
-    return helpers.reparametrize_instance(default_return_type, [Instance(outer_model_info, [])])
+    return helpers.reparametrize_instance(default_return_type, [outer_model_info.self_type])
 
 
 def get_field_type_from_lookup(

tests/typecheck/managers/querysets/test_from_queryset.yml

@@ -43,6 +43,31 @@
                 class MyModelWithoutSelf(models.Model):
                     objects = ManagerWithoutSelf()
 
+-   case: from_queryset_model_inheritance
+    main: |
+        from myapp.models import Base, Sub
+        reveal_type(Base.objects)  # N: Revealed type is "myapp.models.MyManager[myapp.models.Base]"
+        reveal_type(Sub.objects)  # N: Revealed type is "myapp.models.MyManager[myapp.models.Sub]"
+    installed_apps:
+        - myapp
+    files:
+        -   path: myapp/__init__.py
+        -   path: myapp/models.py
+            content: |
+                from typing import ClassVar
+                from typing_extensions import Self
+                from django.db.models import Model
+                from django.db.models.manager import BaseManager
+                from django.db.models.query import QuerySet
+
+                MyManager = BaseManager.from_queryset(QuerySet, "MyManager")
+
+                class Base(Model):
+                    objects: ClassVar[MyManager[Self]] = MyManager()
+
+                class Sub(Base):
+                    pass
+
 -   case: from_queryset_with_base_manager
     main: |
         from myapp.models import MyModel

tests/typecheck/managers/test_managers.yml

@@ -583,6 +583,7 @@
         -   path: myapp/models.py
             content: |
                 from typing import ClassVar, TypeVar
+                from typing_extensions import Self
                 from django.db import models
 
                 T = TypeVar("T", bound="MyModel")
@@ -597,7 +598,7 @@
                     pass
 
                 class MySubModel(MyModel):
-                    objects: ClassVar[MySubManager["MySubModel"]] = MySubManager()
+                    objects: ClassVar[MySubManager[Self]] = MySubManager()
 
 -   case: subclass_manager_without_type_parameters_disallow_any_generics
     main: |