Fix ForeignKey type for self-reference defined in the abstract model (#200)

test-data/typecheck/fields/test_related.yml

@@ -623,4 +623,28 @@
                 class TransactionLog(models.Model):
                     transaction = models.ForeignKey(Transaction, on_delete=models.CASCADE)
 
-                Transaction().test()
+                Transaction().test()
+
+
+-   case: resolve_primary_keys_for_foreign_keys_with_abstract_self_model
+    main: |
+        from myapp.models import User
+        reveal_type(User().parent)  # N: Revealed type is 'myapp.models.User*'
+        reveal_type(User().parent_id)  # N: Revealed type is 'builtins.int*'
+
+        reveal_type(User().parent2)  # N: Revealed type is 'Union[myapp.models.User, None]'
+        reveal_type(User().parent2_id)  # N: Revealed type is 'Union[builtins.int, None]'
+    installed_apps:
+        - myapp
+    files:
+        -   path: myapp/__init__.py
+        -   path: myapp/models.py
+            content: |
+                from django.db import models
+                class AbstractUser(models.Model):
+                    parent = models.ForeignKey('self', on_delete=models.CASCADE)
+                    parent2 = models.ForeignKey('self', null=True, on_delete=models.CASCADE)
+                    class Meta:
+                        abstract = True
+                class User(AbstractUser):
+                    pass