allow django models to declare their own id primary key

pyrefly/lib/alt/class/class_field.rs

@@ -4333,6 +4333,22 @@ impl<'ctx, 'answer, Ans: LookupAnswer> AnswersSolver<'ctx, 'answer, Ans> {
             else {
                 continue;
             };
+            // Django gives a model without its own primary key a synthesized `id: int`,
+            // including abstract bases like `AbstractBaseUser` (stubs omit `Meta.abstract`,
+            // so we can't tell them apart). Django only adds that field to the concrete model
+            // when no pk is declared, so a child declaring `id` as its primary key replaces it
+            // rather than overriding it. An explicitly declared parent `id` is still checked.
+            if field_name.as_str() == "id"
+                && metadata
+                    .django_model_metadata()
+                    .and_then(|dm| dm.custom_primary_key_field.as_ref())
+                    == Some(field_name)
+                && self
+                    .get_non_synthesized_class_member(parent_cls, field_name)
+                    .is_none()
+            {
+                continue;
+            }
             // `__call__` is checked against a Protocol parent only, unless the user
             // opts in with `@override`. Implementing a callable interface is
             // ubiquitous - argparse actions, auth handlers, metaclasses - and

pyrefly/lib/test/django/auto_generated_fields.rs

@@ -165,3 +165,45 @@ assert_type(obj.id, str)
 assert_type(obj.pk, str)
 "#,
 );
+
+// Abstract bases without their own pk get a synthesized `id: int`. A child that
+// declares its own `id` primary key should not be flagged as overriding it.
+// https://github.com/meta/pyrefly/issues/4596
+django_testcase!(
+    test_custom_id_pk_overrides_synthesized_id,
+    r#"
+from typing import assert_type
+import uuid
+from django.contrib.auth.models import AbstractBaseUser, PermissionsMixin
+from django.db import models
+
+class User(AbstractBaseUser, PermissionsMixin):
+    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
+
+class Base(models.Model):
+    class Meta:
+        abstract = True
+
+class Child(Base):
+    id = models.CharField(max_length=36, primary_key=True)
+
+assert_type(User().id, uuid.UUID)
+assert_type(User().pk, uuid.UUID)
+assert_type(Child().id, str)
+assert_type(Child().pk, str)
+"#,
+);
+
+// An `id` that is not the primary key is still checked against the synthesized one.
+django_testcase!(
+    test_non_pk_id_still_checked_against_synthesized_id,
+    r#"
+from django.db import models
+
+class Base(models.Model):
+    pass
+
+class Child(Base):
+    id = models.CharField(max_length=36)  # E: `Child.id` overrides parent class `Base`
+"#,
+);