Functions with same signature but different parameter names.

[sharmaeklavya2]

def is_prime(n):
    # type: (int) -> bool
    return all(n % p != 0 for p in range(2, n))

def is_palindrome(m):
    # type: (int) -> bool
    return str(m) == ''.join(reversed(str(m)))

list1 = [is_prime, is_palindrome]
list2 = [is_prime, is_prime]

reveal_type(list1)
reveal_type(list2)

In this code, is_prime and is_palindrome have the same signature def (builtins.int) -> builtins.bool but different parameter names.

These are the revealed types:

• list1: builtins.list[builtins.function*]
• list2: builtins.list[def (n: builtins.int) -> builtins.bool]

I think the type of list1 should have been builtins.list[def (builtins.int) -> builtins.bool].

[sharmaeklavya2]

mypy behaved differently in 0.4.6. In mypy 0.4.6, revealed type of list1 was builtins.list[def (m: builtins.int) -> builtins.bool], which was wrong.

[JukkaL]

This is a side effect of recent changes to callable types. The previous behavior was better for this example. In technical terms, mypy should be more clever about joins of callable types in general.

A simple workaround is to give list1 an explicit annotation:

...
list1 = [is_prime, is_palindrome]  # type: List[Callable[[int], bool]]