Open
Description
Summary
The following works in pyright, but not in pyrefly, mypy, or (which is why I'm here!) ty:
from __future__ import annotations
from dataclasses import dataclass
from typing_extensions import (
Generic,
Sequence,
TypeVar,
assert_type,
)
T = TypeVar("T")
@dataclass
class Agent(Generic[T]):
output_type: Sequence[type[T]]
class Foo:
pass
class Bar:
pass
# pyright - works
# mypy - error: Expression is of type "Agent[object]", not "Agent[Foo | Bar]" [assert-type]
# pyrefly - assert_type(Agent[Foo], Agent[Bar | Foo]) failed + Argument `list[type[Bar] | type[Foo]]` is not assignable to parameter `output_type` with type `Sequence[type[Foo]]` in function `Agent.__init__`
# ty - `Agent[Foo | Bar]` and `Agent[Unknown]` are not equivalent types
assert_type(Agent([Foo, Bar]), Agent[Foo | Bar])
# pyright - works
# mypy - error: Expression is of type "Agent[Never]", not "Agent[int | str]" [assert-type]
# pyrefly - assert_type(Agent[int], Agent[str | int]) failed + Argument `list[type[str] | type[int]]` is not assignable to parameter `output_type` with type `Sequence[type[int]]` in function `Agent.__init__`
# ty - `Agent[int | str]` and `Agent[Unknown]` are not equivalent types
assert_type(Agent([int, str]), Agent[int | str])
# works
assert_type(Agent[Foo | Bar]([Foo, Bar]), Agent[Foo | Bar])
# works
assert_type(Agent[int | str]([int, str]), Agent[int | str])It would be great to see this work in ty, but if there's a good reason the other 2 out of 3 typecheckers don't support this I'd love to understand why!
- This is related to a new PydanticAI feature, if you're curious check out Support functions as output_type, as well as lists of functions and other types pydantic/pydantic-ai#1785 (comment)
- Issues for other type checkers:
Version
ty 0.0.1-alpha.6