'Cannot call function of unknown type' for sequence of callables with different signatures

Bug Report

When working with sequences of callables, if all callables in the sequence do not have the same signature mypy will raise false positives when trying to access and call the callables.

To Reproduce

def identity(x: int) -> int:
    return x

def double(x: int) -> int:
    return x * 2

def add(x: int, y: int) -> int:
    return x + y

calls_same_signatures = (
    (identity, (1,)),
    (double, (2,)),
)

calls_different_signatures = (
    (identity, (1,)),
    (add, (1, 2)),
)

for f1, args1 in calls_same_signatures:
    f1(*args1) # type checks

for f2, args2 in calls_different_signatures:
    f2(*args2) # mypy says: Cannot call function of unknown type

Trying to fix this with annotations results in what may be a more revealing error?

from typing import Callable, Sequence, Tuple

def identity(x: int) -> int:
    return x

def double(x: int) -> int:
    return x * 2

def add(x: int, y: int) -> int:
    return x + y

calls_same_signatures: Sequence[Tuple[Callable[..., int], Tuple[int, ...]]]
calls_same_signatures = (
    (identity, (1,)),
    (double, (2,)),
)

calls_different_signatures: Sequence[Tuple[Callable[..., int], Tuple[int, ...]]]
calls_different_signatures = (
    (identity, (1,)),
    (add, (1, 2)),
)

f1: Callable[..., int]
for f1, args1 in calls_same_signatures: # type checks
    f1(*args1)

f2: Callable[..., int]
for f2, args2 in calls_different_signatures:  # mypy says: Incompatible types in assignment (expression has type "function", variable has type "Callable[..., int]")
    f2(*args2)

Expected Behavior

I'd expect this to type check.
I'm not sure if it might be a contravariant vs. covariant thing? That is, does this issue stem from the question over whether the function is a Callable[[int], int] or a Callable[..., int] when it comes out of the sequence?

Actual Behavior

Mypy raises an error when attempting to call functions in calls_different_signatures,
Cannot call function of unknown type in the first example, Incompatible types in assignment (expression has type "function", variable has type "Callable[..., int]") in the second.

Your Environment

• Mypy version used: 0.782
• Mypy command-line flags: none
• Mypy configuration options from mypy.ini (and other config files): none
• Python version used: 3.6.5
• Operating system and version: OS X 10.15.7

まず、提供された再現コードを mypy で実行し、均一なシグネチャのシーケンスと混在したシグネチャのシーケンスについて推論された型を比較します。ループ変数に関係する callable と tuple の推論経路を追跡し、注釈付きの例を使って報告された代入の挙動を絞り込みます。混在したシグネチャの例が期待どおり型チェックを通過し、互換性のない呼び出しを誤って受け入れることがない状態になれば完了です。