allow to use fields as Field objects outside Model classes

Author: mkurnikov

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

@@ -90,9 +90,12 @@ class Field(RegisterLookupMixin, Generic[_ST, _GT]):
     # class access
     @overload
     def __get__(self: _T, instance: None, owner) -> _T: ...
-    # instance access
+    # Model instance access
     @overload
-    def __get__(self, instance, owner) -> _GT: ...
+    def __get__(self, instance: Model, owner) -> _GT: ...
+    # non-Model instances
+    @overload
+    def __get__(self: _T, instance, owner) -> _T: ...
     def deconstruct(self) -> Any: ...
     def set_attributes_from_name(self, name: str) -> None: ...
     def db_type(self, connection: Any) -> str: ...

test-data/typecheck/fields/test_base.yml

@@ -123,4 +123,12 @@
             content: |
                 from django.db import models
                 class MyUser(models.Model):
-                    name = models.CharField(max_length=100)
+                    name = models.CharField(max_length=100)
+
+-   case: fields_on_non_model_classes_resolve_to_field_type
+    main: |
+        from django.db import models
+        class MyClass:
+            myfield: models.IntegerField[int, int]
+        reveal_type(MyClass.myfield)  # N: Revealed type is 'django.db.models.fields.IntegerField[builtins.int, builtins.int]'
+        reveal_type(MyClass().myfield)  # N: Revealed type is 'django.db.models.fields.IntegerField[builtins.int, builtins.int]'