Can not pass generic function to generic function

[sharkdp]

The following example …

from typing import Callable

def invoke[A, B](fn: Callable[[A], B], value: A) -> B:
    return fn(value)

def identity[T](x: T) -> T:
    return x

invoke(identity, 1)

(https://play.ty.dev/6dfb9951-b78f-4791-af82-151a1c694a7c)

… currently fails with this error:

error[invalid-argument-type]: Argument to function `invoke` is incorrect
  --> /home/shark/playground/test.py:12:8
   |
12 | invoke(identity, 1)
   |        ^^^^^^^^ Expected `(Literal[1], /) -> Unknown`, found `def identity[T](x: T@identity) -> T@identity`
   |
info: Function defined here
 --> /home/shark/playground/test.py:4:5
  |
4 | def invoke[A, B](fn: Callable[[A], B], value: A) -> B:
  |     ^^^^^^       -------------------- Parameter declared here
5 |     return fn(value)
  |
info: rule `invalid-argument-type` is enabled by default

I am reporting this in addition to #623, because it seems like this is not really related to the shortcomings of the current solver, but rather to the way we handle assignability of the generic identity function argument to the call(?).

[carljm]

Is this the same as #95 ?

[sharkdp]

Yes, very much looks like it. I'll copy over my example to make sure it gets resolved when that issue is fixed.

[sharkdp]

This is fixable independently from #95, so I'm reopening it for now.