bad-return-type with "Actually returned: Any" even without --no-return-any

[cebtenzzre]

Description

I am using pytype 2024.10.11.

'foo' is just a placeholder in the below example; in the real code it is a file path that is passed through get_or_compute to the compute function and used as a cache key.

I would use the pytype equivalent of mypy's --no-warn-return-any to silence this kind of warning, but it seems like it's supposed to be opt-in in the first place (--no-return-any).

Possibly related (similar error): #1686 (comment)

Example Code

from typing import Any, Callable, Literal, TypeVar, overload

T = TypeVar('T')

class Cache:
    def __init__(self) -> None:
        self.cache: dict[str, dict[str, Any]] = {'foo': {}}

    @overload
    def get_or_compute(self, key: Literal['str'], compute: Callable[[], str]) -> str: ...

    @overload
    def get_or_compute(self, key: Literal['int'], compute: Callable[[], int]) -> int: ...

    def get_or_compute(self, key: str, compute: Callable[[], T]) -> T:
        entry = self.cache['foo']
        if key not in entry:
            entry[key] = compute()
        return entry[key]

cache = Cache()

def compute_str() -> str:
    print('computing str')
    return 'a'

def compute_int() -> int:
    print('computing int')
    return 1

def get_str() -> str:
    return cache.get_or_compute('str', compute_str)

def get_int() -> int:
    return cache.get_or_compute('int', compute_int)

print(f'int: {get_int()} str: {get_str()!r}')
print(f'int: {get_int()} str: {get_str()!r}')

Steps to Reproduce

$ python repr.py
computing int
computing str
int: 1 str: 'a'
int: 1 str: 'a'

$ mypy --strict --no-warn-return-any repr.py
Success: no issues found in 1 source file

$ pytype-single repr.py
repr.py:19:9: error: in get_or_compute: bad option 'int' in return type [bad-return-type]
           Expected: str
  Actually returned: Any

        return entry[key]
        ~~~~~~~~~~~~~~~~~

Called from (traceback):
  line 37, in current file
  line 32, in get_str

For more details, see https://google.github.io/pytype/errors.html#bad-return-type