support generic TypedDict

[RyanSaxe]

Summary

TypeVars do not seem to be properly handled inside TypedDicts

from typing import TypedDict, reveal_type


class TestDictExample[T](TypedDict):
    id: int
    name: str
    active: bool
    bug: T


class Example[T]:
    def __init__(self, data: TestDictExample[T]) -> None:
        self.attr: TestDictExample[T] = data

    def do_something(self) -> T:
        value = self.attr["bug"] # ty thinks this is Unknown instead of T
        name = self.attr["name"] # ty correctly gets this as str
        return value

https://play.ty.dev/fa58789a-4d72-4f76-802d-7dafe74e52b8

Version

ty 0.0.5

[carljm]

Thanks for the report!

[AlexWaygood]

Huh, I'm pretty sure we have some support for generic TypedDicts. We definitely have a bunch of tests that use generic TypedDicts

[carljm]

It looks like what we have is pretty limited -- we appear to keep track of the specialization and use it when validating a dict literal against the TypedDict, but we don't display it as part of the type display, or take it into account when inferring a type from __getitem__.

We could re-word the title here, but based on what I'm seeing I think the current title is fair :)

[sharifhsn]

Closed by astral-sh/ruff#23926.

Repro:

from typing import TypedDict
from typing_extensions import reveal_type

class TestDictExample[T](TypedDict):
    id: int
    name: str
    active: bool
    bug: T

class Example[T]:
    def __init__(self, data: TestDictExample[T]) -> None:
        self.attr: TestDictExample[T] = data

    def do_something(self) -> T:
        value = self.attr["bug"]
        reveal_type(value)  # ty: should be T
        name = self.attr["name"]
        reveal_type(name)
        return value

ty 0.0.23:

Revealed type: `Unknown`
Revealed type: `str`

ty 0.0.24:

Revealed type: `T@Example`
Revealed type: `str`