[asukaminato0721]

Summary

Fixes #3062

cached properties are now treated as writable for override consistency, using the getter return type and promoting inferred literal returns like return True to match class-variable inference.

Test Plan

add test

[Copilot]

Copilot encountered an error and was unable to review this pull request. You can try again by re-requesting a review.

[meta-codesync]

@yangdanny97 has imported this pull request. If you are a Meta employee, you can view this in D107101300.

[stroxler]

Thanks! This looks like it's probably headed in a good direction, I like the mypy_primer delta.

Based on AI review, I think we need to clear up some more behaviors before we can merge:

This PR is bigger than it needs to be

Maybe split the unrelated signature-help change into a separate PR. Its tests should include whitespace before an existing argument: currently every expected index also equals arguments.len(), so the tests pass even if token counting returns None.

Literal widening only happens in the compatibility check

[class_field.rs:5830–5842](https://github.com/meta/pyrefly/blob/a8e81e550b8d322bdab90e95652953558eec6de5/pyrefly/lib/alt/class/class_field.rs#L5830-L5842)

The helper widens an inferred Literal[True] return to bool, but actual cached-property reads and assignment checking retain Literal[True]. This accepts substitutions that violate the attribute’s reported type:

• A writable protocol declares x: bool.
• A class implements x as a cached property returning unannotated True.
• A function taking the protocol assigns False to x.
• Pyrefly still accepts passing the resulting value to a function requiring Literal[True].

Verified: the patched binary reports zero errors under default; CPython fails the corresponding assertion. The unpatched binary rejects the protocol conversion. The inheritance case has the same inconsistency: writing False through the base type is accepted, while writing it directly through the subclass is rejected.

Fix: establish one cached-property value type used consistently for reads, writes, and compatibility checks. Add both protocol and inherited-write regressions.

Read-only failures get a mutable-attribute diagnostic

[class_field.rs:5915–5931](https://github.com/meta/pyrefly/blob/a8e81e550b8d322bdab90e95652953558eec6de5/pyrefly/lib/alt/class/class_field.rs#L5915-L5931)

Overriding a frozen dataclass’s x: int with a cached property returning str now reports bad-override-mutable-attribute, despite the parent attribute being read-only. This matters for configurations that control those error kinds separately. Add a negative read-only-parent test and preserve the appropriate diagnostic classification.

[github-actions]

Diff from mypy_primer, showing the effect of this PR on open source code:

============================================================
SUMMARY
============================================================
Total: +12 new errors, -74 fixed errors
By preset: +5/-74 (default), +7/-74 (strict)

Projects with changes (4):
  openlibrary: +1 -0
  jax: +2 -0
  django-stubs: +5 -74
  core: +4 -0
============================================================

FULL DIFF DETAILS
------------------------------------------------------------

openlibrary (https://github.com/internetarchive/openlibrary)
+ ERROR openlibrary/core/lists/model.py:662:17-41: Unused `# type: ignore` comment [unused-type-ignore]

jax (https://github.com/google/jax)
+ ERROR jax/_src/mesh.py:363:27-58: Unused `# pyrefly: ignore` comment for code(s): bad-override [unused-ignore]
+ ERROR jax/_src/mesh.py:551:27-58: Unused `# pyrefly: ignore` comment for code(s): bad-override [unused-ignore]

django-stubs (https://github.com/typeddjango/django-stubs)
- ERROR django-stubs/contrib/gis/db/backends/mysql/features.pyi:17:9-45: Class member `DatabaseFeatures.supports_geometry_field_unique_index` overrides parent class `BaseSpatialFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/contrib/gis/db/backends/mysql/operations.pyi:17:9-16: Class member `MySQLOperations.mariadb` overrides parent class `BaseSpatialOperations` in an inconsistent manner [bad-override]
- ERROR django-stubs/contrib/gis/db/backends/mysql/operations.pyi:20:9-14: Class member `MySQLOperations.mysql` overrides parent class `BaseSpatialOperations` in an inconsistent manner [bad-override]
- ERROR django-stubs/contrib/gis/db/backends/mysql/operations.pyi:23:9-15: Class member `MySQLOperations.select` overrides parent class `BaseSpatialOperations` in an inconsistent manner [bad-override]
- ERROR django-stubs/contrib/gis/db/backends/mysql/operations.pyi:26:9-18: Class member `MySQLOperations.from_text` overrides parent class `BaseSpatialOperations` in an inconsistent manner [bad-override]
+ ERROR django-stubs/contrib/gis/db/backends/mysql/operations.pyi:26:9-18: Class member `MySQLOperations.from_text` overrides parent class `BaseSpatialOperations` in an inconsistent manner [bad-override-mutable-attribute]
- ERROR django-stubs/contrib/gis/db/backends/mysql/operations.pyi:34:9-30: Class member `MySQLOperations.unsupported_functions` overrides parent class `BaseSpatialOperations` in an inconsistent manner [bad-override]
- ERROR django-stubs/contrib/gis/db/backends/oracle/introspection.pyi:10:9-27: Class member `OracleIntrospection.data_types_reverse` overrides parent class `DatabaseIntrospection` in an inconsistent manner [bad-override]
- ERROR django-stubs/contrib/gis/db/backends/postgis/operations.pyi:52:9-23: Class member `PostGISOperations.function_names` overrides parent class `BaseSpatialOperations` in an inconsistent manner [bad-override]
- ERROR django-stubs/contrib/gis/db/backends/postgis/operations.pyi:55:9-24: Class member `PostGISOperations.spatial_version` overrides parent class `BaseSpatialOperations` in an inconsistent manner [bad-override]
- ERROR django-stubs/contrib/gis/db/backends/spatialite/features.pyi:10:9-31: Class member `DatabaseFeatures.supports_area_geodetic` overrides parent class `BaseSpatialFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/contrib/gis/db/backends/spatialite/operations.pyi:26:9-30: Class member `SpatiaLiteOperations.unsupported_functions` overrides parent class `BaseSpatialOperations` in an inconsistent manner [bad-override]
- ERROR django-stubs/contrib/gis/db/backends/spatialite/operations.pyi:29:9-24: Class member `SpatiaLiteOperations.spatial_version` overrides parent class `BaseSpatialOperations` in an inconsistent manner [bad-override]
- ERROR django-stubs/contrib/postgres/indexes.pyi:16:9-24: Class member `PostgresIndex.max_name_length` overrides parent class `Index` in an inconsistent manner [bad-override]
- ERROR django-stubs/core/handlers/asgi.pyi:35:9-12: Class member `ASGIRequest.GET` overrides parent class `HttpRequest` in an inconsistent manner [bad-override]
- ERROR django-stubs/core/handlers/asgi.pyi:42:9-16: Class member `ASGIRequest.COOKIES` overrides parent class `HttpRequest` in an inconsistent manner [bad-override]
- ERROR django-stubs/core/handlers/wsgi.pyi:27:9-12: Class member `WSGIRequest.GET` overrides parent class `HttpRequest` in an inconsistent manner [bad-override]
- ERROR django-stubs/core/handlers/wsgi.pyi:30:9-16: Class member `WSGIRequest.COOKIES` overrides parent class `HttpRequest` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/mysql/features.pyi:38:9-33: Class member `DatabaseFeatures.minimum_database_version` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
+ ERROR django-stubs/db/backends/mysql/features.pyi:38:9-33: Class member `DatabaseFeatures.minimum_database_version` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override-mutable-attribute]
- ERROR django-stubs/db/backends/mysql/features.pyi:41:9-24: Class member `DatabaseFeatures.test_collations` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
+ ERROR django-stubs/db/backends/mysql/features.pyi:41:9-24: Class member `DatabaseFeatures.test_collations` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override-mutable-attribute]
- ERROR django-stubs/db/backends/mysql/features.pyi:44:9-26: Class member `DatabaseFeatures.django_test_skips` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/mysql/features.pyi:47:9-25: Class member `DatabaseFeatures.allows_auto_pk_0` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/mysql/features.pyi:50:9-31: Class member `DatabaseFeatures.update_can_self_select` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/mysql/features.pyi:53:9-36: Class member `DatabaseFeatures.can_introspect_foreign_keys` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/mysql/features.pyi:56:9-33: Class member `DatabaseFeatures.introspected_field_types` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/mysql/features.pyi:59:9-39: Class member `DatabaseFeatures.can_return_columns_from_insert` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/mysql/features.pyi:65:9-30: Class member `DatabaseFeatures.has_zoneinfo_database` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/mysql/features.pyi:70:9-42: Class member `DatabaseFeatures.supports_column_check_constraints` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/mysql/features.pyi:76:9-41: Class member `DatabaseFeatures.can_introspect_check_constraints` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/mysql/features.pyi:79:9-33: Class member `DatabaseFeatures.has_select_for_update_of` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/mysql/features.pyi:82:9-34: Class member `DatabaseFeatures.supported_explain_formats` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/mysql/features.pyi:88:9-32: Class member `DatabaseFeatures.ignores_table_name_case` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/mysql/features.pyi:91:9-37: Class member `DatabaseFeatures.supports_default_in_lead_lag` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/mysql/features.pyi:97:9-34: Class member `DatabaseFeatures.can_introspect_json_field` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/mysql/features.pyi:100:9-39: Class member `DatabaseFeatures.supports_index_column_ordering` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/mysql/features.pyi:103:9-36: Class member `DatabaseFeatures.supports_expression_indexes` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/mysql/features.pyi:106:9-37: Class member `DatabaseFeatures.supports_select_intersection` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/mysql/features.pyi:112:9-37: Class member `DatabaseFeatures.supports_expression_defaults` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/mysql/features.pyi:115:9-30: Class member `DatabaseFeatures.has_native_uuid_field` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/mysql/features.pyi:118:9-37: Class member `DatabaseFeatures.allows_group_by_selected_pks` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/mysql/features.pyi:121:9-27: Class member `DatabaseFeatures.supports_any_value` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/mysql/features.pyi:124:9-32: Class member `DatabaseFeatures.supports_uuid4_function` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/mysql/features.pyi:130:9-32: Class member `DatabaseFeatures.supports_uuid7_function` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/oracle/features.pyi:54:9-40: Class member `DatabaseFeatures.supports_json_negative_indexing` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/oracle/features.pyi:57:9-26: Class member `DatabaseFeatures.django_test_skips` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/oracle/features.pyi:60:9-33: Class member `DatabaseFeatures.introspected_field_types` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/oracle/features.pyi:63:9-24: Class member `DatabaseFeatures.test_collations` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/oracle/features.pyi:66:9-40: Class member `DatabaseFeatures.supports_collation_on_charfield` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/oracle/features.pyi:69:9-42: Class member `DatabaseFeatures.supports_primitives_in_json_field` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/oracle/features.pyi:72:9-33: Class member `DatabaseFeatures.supports_frame_exclusion` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/oracle/features.pyi:75:9-40: Class member `DatabaseFeatures.supports_comparing_boolean_expr` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/oracle/features.pyi:80:9-27: Class member `DatabaseFeatures.bare_select_suffix` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/oracle/features.pyi:83:9-31: Class member `DatabaseFeatures.supports_tuple_lookups` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/oracle/features.pyi:86:9-32: Class member `DatabaseFeatures.supports_uuid4_function` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/oracle/features.pyi:89:9-43: Class member `DatabaseFeatures.supports_uuid4_function_in_default` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/oracle/features.pyi:92:9-42: Class member `DatabaseFeatures.supports_stored_generated_columns` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/oracle/features.pyi:95:9-34: Class member `DatabaseFeatures.supports_bit_aggregations` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/postgresql/features.pyi:51:9-32: Class member `DatabaseFeatures.supports_uuid7_function` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/postgresql/features.pyi:54:9-38: Class member `DatabaseFeatures.supports_uuid7_function_shift` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/postgresql/features.pyi:57:9-26: Class member `DatabaseFeatures.django_test_skips` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/postgresql/features.pyi:60:9-38: Class member `DatabaseFeatures.django_test_expected_failures` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/postgresql/features.pyi:65:9-25: Class member `DatabaseFeatures.max_query_params` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/postgresql/features.pyi:68:9-52: Class member `DatabaseFeatures.prohibits_null_characters_in_text_exception` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
+ ERROR django-stubs/db/backends/postgresql/features.pyi:68:9-52: Class member `DatabaseFeatures.prohibits_null_characters_in_text_exception` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override-mutable-attribute]
- ERROR django-stubs/db/backends/postgresql/features.pyi:71:9-33: Class member `DatabaseFeatures.introspected_field_types` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/sqlite3/features.pyi:14:9-32: Class member `DatabaseFeatures.supports_uuid7_function` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/sqlite3/features.pyi:17:9-26: Class member `DatabaseFeatures.django_test_skips` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/sqlite3/features.pyi:20:9-33: Class member `DatabaseFeatures.introspected_field_types` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/sqlite3/features.pyi:26:9-28: Class member `DatabaseFeatures.supports_json_field` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/backends/sqlite3/features.pyi:35:9-39: Class member `DatabaseFeatures.can_return_columns_from_insert` overrides parent class `BaseDatabaseFeatures` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/models/expressions.pyi:136:9-24: Class member `CombinedExpression.allowed_default` overrides parent class `Expression` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/models/expressions.pyi:195:9-24: Class member `Func.allowed_default` overrides parent class `Expression` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/models/expressions.pyi:294:9-24: Class member `When.allowed_default` overrides parent class `Expression` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/models/expressions.pyi:307:9-24: Class member `Case.allowed_default` overrides parent class `Expression` in an inconsistent manner [bad-override]
- ERROR django-stubs/db/models/fields/related.pyi:73:9-22: Class member `RelatedField.related_model` overrides parent class `Field` in an inconsistent manner [bad-override]
+ ERROR django-stubs/db/models/fields/related.pyi:73:9-22: Class member `RelatedField.related_model` overrides parent class `Field` in an inconsistent manner [bad-override-mutable-attribute]
- ERROR django-stubs/db/models/lookups.pyi:48:9-24: Class member `Lookup.allowed_default` overrides parent class `Expression` in an inconsistent manner [bad-override]

core (https://github.com/home-assistant/core)
+ ERROR homeassistant/components/recorder/models/state.py:70:42-66: Unused `# type: ignore` comment [unused-type-ignore]
+ ERROR homeassistant/components/recorder/models/state.py:78:43-67: Unused `# type: ignore` comment [unused-type-ignore]
+ ERROR homeassistant/components/recorder/models/state.py:86:42-66: Unused `# type: ignore` comment [unused-type-ignore]
+ ERROR homeassistant/components/recorder/models/state.py:94:49-73: Unused `# type: ignore` comment [unused-type-ignore]

[stroxler]

Great! I think this is almost ready to merge.

But I just realized it's another too-old PR, the import diff is stale so I can't easily finish my review.

Could you close this and reopen? Assign me to the fresh PR when you do While you're at it, there are two more concerns caught in a fresh review that should be pretty easy to fix:

Overload comparison accepts unsafe protocol writes

[class_field.rs:5954–5958](https://github.com/meta/pyrefly/blob/029edfdf6eb4dcf8fa31d6a83b19a75c3b0e3ab5/pyrefly/lib/alt/class/class_field.rs#L5954-L5958)

Compatibility unions all overload returns, while reads and direct writes select overloads using the receiver. A cached property on C[int] can therefore satisfy a writable protocol with x: int | str, despite its actual attribute type being int.

Verified: the unpatched build rejects the conversion; the patched build reports zero errors; writing a string through the protocol then fails an integer assertion in CPython. Direct string assignment remains rejected.

Fix: use receiver-aware getter resolution for compatibility, with both negative broad-protocol and positive narrow-protocol tests.

Literal widening rejects valid inner decorators

[function.rs:783–786](https://github.com/meta/pyrefly/blob/029edfdf6eb4dcf8fa31d6a83b19a75c3b0e3ab5/pyrefly/lib/alt/function.rs#L783-L786)

Widening occurs before inner decorators are checked. With @cached_property outside a decorator requiring a function returning Literal[True], an unannotated return True is prematurely presented as bool.

Verified: unpatched Pyrefly, mypy, pyright, and CPython accept the example; patched Pyrefly rejects it.

Fix: preserve the original return while checking inner decorators, then apply cached-value normalization at the resulting getter/value boundary.

[stroxler]

I'm going to leave this open since it's mostly and I don't want to lose track of it - again, to get this merged the quickest path is for you to close, reopen (with adjustments for the latest round of review), and assign me. I think it's about ready, the imported diff is just too old for me to work with