Type system features

This page summarizes the support for various type system features in ty.

Dataclasses

Feature	Status
`@dataclass` decorator (`init`, `repr`, `eq`, `order`, `frozen`, `match_args`, `kw_only`, `slots`, `weakref_slot`, `unsafe_hash`)	✅
`field()` (`default`, `default_factory`, `init`, `kw_only`, `doc`, `repr`, `hash`, `compare`)	✅
`InitVar[…]`, `ClassVar[…]` exclusion, `KW_ONLY` sentinel	✅
`fields()`, `__dataclass_fields__`	✅
`Final` fields	✅
Inheritance, generic dataclasses, descriptor-typed fields	✅
`replace()`, `__replace__`	⚠️ `__replace__` works, `replace()` returns `Unknown`
`asdict()`	⚠️ incorrectly accepts class objects
`astuple()`	⚠️ not tested
`make_dataclass()`, `is_dataclass()`	⚠️ not tested
Diagnostic: frozen dataclass inheriting from non-frozen	⚠️ not tested
Diagnostic: non-default field after default field	❌ #111
Diagnostic: `order=True` with custom comparison methods	❌ #111
Diagnostic: `frozen=True` with `__setattr__`/`__delattr__`	❌ #111
`__post_init__` signature validation	❌ #111

Feature	Status
Function-based, metaclass-based, base-class-based transformers	✅
`eq_default`, `order_default`, `kw_only_default` parameters	✅
`frozen_default` parameter	⚠️ metaclass override not working
`field_specifiers` (`init`, `default`, `default_factory`, `factory`, `kw_only`, `alias`)	✅
`field_specifiers` (`converter`)	❌ #1327