Type variable in container of callable is not solved

[layday]

Describe the bug
When a type variable T is inside a container which is a Callable parameter (a callback), which is itself a parameter of a function whose return type is the return type of the Callable, an unsolved copy of T is left dangling in a union.

To Reproduce
Type check the snippet below.

Expected behavior
That the type of qux([1.], bar) would be float.

Screenshots or Code

from typing import Callable, Sequence, TypeVar

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

def foo(value: T) -> T:
    ...

def bar(values: Sequence[T]) -> T:
    ...

def baz(
    value: T,
    callback: Callable[[T], U],
) -> U:
    ...

def qux(
    values: Sequence[T],
    callback: Callable[[Sequence[T]], U],
) -> U:
    ...

reveal_type(baz(1., foo))       # Type of "baz(1, foo)" is "float"
reveal_type(qux([1.], foo))     # Type of "qux([1], foo)" is "Sequence[float]"
reveal_type(qux([1.], bar))     # Type of "qux([1], bar)" is "float | T@bar" - should be "float"

VS Code extension or command-line
Either, 1.1.122 - used to work in versions prior to 1.1.122.

[erictraut]

Thanks for the bug report. This will be fixed in the next release.

Interestingly, mypy reports errors in all three of these cases:

test7.py:29: error: Argument 2 to "baz" has incompatible type "Callable[[T], T]"; expected "Callable[[float], T]"
test7.py:30: note: Revealed type is 'T`-1'
test7.py:30: error: Argument 2 to "qux" has incompatible type "Callable[[T], T]"; expected "Callable[[Sequence[float]], T]"
test7.py:32: note: Revealed type is 'T`-1'
test7.py:32: error: Argument 2 to "qux" has incompatible type "Callable[[Sequence[T]], T]"; expected "Callable[[Sequence[float]], T]"

[layday]

Huh, interesting, can you not type generic callbacks at all with mypy?

[erictraut]

This is now addressed in pyright 1.1.123, which I just published. It will also be included in the next release of pylance.