Type checkers

Use Pyright for the best type inference with Signified. Pyrefly is a usable alternative with caveats.

Assessed on 2026-10-10 with Python 3.14.3 and Signified 0.7.0 (revision 9de4e8b). The inference suite checks 765 inferred types and 60 operations that should be rejected.

Checker	Version	Wrong types (of 765)	Invalid operations flagged (of 60)	Recommendation
Pyright	1.1.414	0	60	Recommended
Pyrefly	1.3.2	33	42	Usable with caveats
ty	0.0.86	247	56	Not recommended yet
mypy	2.4.0	165	34	Not recommended

• Pyrefly: abs, math.trunc, math.floor, and math.ceil on signals infer Unknown, and divmod infers the wrong type for mixed, Decimal, or reflected operands. It accepts round and the math functions on unsupported values, and reports an error when calling a wrapped callable object.
• ty: unref and Binding rarely infer the right type, many operators infer Unknown, and some valid operations are rejected, such as Signal(10.0) // Signal(2.0).
• mypy: unref and Binding reject valid arguments and infer Never. Operators on signals mostly infer correctly. Mypy ran with --check-untyped-defs so test bodies were checked.

Even with Pyright, attributes read through a signal, such as Signal(person).name, and deep_unref results are typed Any, so a misspelled attribute is not caught. Functions decorated with @computed or @effect keep their return type but do not check their arguments.