Type checking is not working for parameters entered inline with a function

[williamjamir]

Describe the bug
Not sure if this is the correct project to report this issue; it may look like a mypy issue, but I could not reproduce it with any example that was not from pandas-stubs.

Mypy is not complaining about a wrong pd.Series when passing directly in a function.

To Reproduce

Example not displaying error:

from __future__ import annotations

import pandas as pd

def some_function(param: pd.Series[str]) -> pd.Series[float]:
    return param.astype(float)

some_function(param=pd.Series([1.0, 1.0, 1.0], dtype=float)

mypy doesn't complain

>>>mypy test.py                                                   
Success: no issues found in 1 source file

But, if this value is kept in a variable, the error is shown.

from __future__ import annotations

import pandas as pd


def some_function(param: pd.Series[str]) -> pd.Series[float]:
    return param.astype(float)


some_value = pd.Series([1.0, 1.0, 1.0], dtype=float)
some_function(some_value)

>>> mypy test.py
/tmp/test.py:11: error: Argument 1 to "some_function" has incompatible type "Series[float]"; expected "Series[str]"  [arg-type]
Found 1 error in 1 file (checked 1 source file)

Please complete the following information:

• OS: MacOS M1

• OS Version Ventura 13.0

• python version: 3.9.12 (Can see the same issue on Python 3.10)

• version of type checker: mypy 0.982 (compiled: yes)

• version of installed pandas-stubs
  pandas==1.5.1
  pandas-stubs==1.5.1.221024

Additional context
Add any other context about the problem here.

[Dr-Irv]

It's a mypy bug. I just reported it here: python/mypy#14009

[Dr-Irv]

Still a mypy bug in version 0.990

[Dr-Irv]

Based on discussion in python/mypy#14009 (see python/mypy#14009 (comment) ), this is a subtle feature of how type checkers work.

So we can't fix this because we need to support Series with unspecified types.