Cannot resolve `TypeDict` into `Union` *only* when the `Union` contains an `Awaitable`

[iwahbe]

Describe the bug

I'm seeing pyright fail to type a TypedDict only when it's resolved into a union that includes a third type (in my example, Awaitable[T]). Here is my repro:

from typing import Awaitable, Callable, Generic, TypedDict, TypeVar, Union

T = TypeVar("T")
U = TypeVar("U")

Input = Union[T, Awaitable[T], "Output[T]"]


class Output(Generic[T]):
    def apply(self, func: Callable[[T], Input[U]]) -> "Output[U]": ...


class D(TypedDict):
    key: str


def accept(x: Input[list[D]]) -> None: ...


# OK: dict literal directly in call has downward type context.
accept([{"key": "v"}])

# ERROR: dict literal inside apply lambda is inferred as dict[str, str], not D.
accept(Output[list[D]]().apply(lambda _: [{"key": "v"}]))

The confusing this is that this makes it type-check without errors:

-Input = Union[T, Awaitable[T], "Output[T]"]
+Input = Union[T, "Output[T]"]

Full non-erroring code

from typing import Awaitable, Callable, Generic, TypedDict, TypeVar, Union

T = TypeVar("T")
U = TypeVar("U")

Input = Union[T, "Output[T]"]


class Output(Generic[T]):
    def apply(self, func: Callable[[T], Input[U]]) -> "Output[U]": ...


class D(TypedDict):
    key: str


def accept(x: Input[list[D]]) -> None: ...


# OK: dict literal directly in call has downward type context.
accept([{"key": "v"}])

# ERROR: dict literal inside apply lambda is inferred as dict[str, str], not D.
accept(Output[list[D]]().apply(lambda _: [{"key": "v"}]))

This was observed running the pyright CLI at version 1.1.408.

---

Notes:

mypy --strict (at version 0.931) type-checks both programs without issue.

#10908 implies that these programs should never type-check, but that obviously the case.