ForwardRef's and recursive type aliases are still broken

[ulidtko]

The minimal Hutton razor doesn't typecheck.

# hutton.py

from typing import Union, Tuple

HuttonRazor = Union[
    int,
    Tuple['HuttonRazor', 'HuttonRazor'],
]

I've tested on these git tags with Python 3.8.2:

• v0.761
• v0.760
• v0.750
• v0.740
• v0.730
• v0.720
• v0.710
• v0.701
• v0.700

None of them work; all emit an error of possible cyclic definition:

hutton.py:5: error: Cannot resolve name "HuttonRazor" (possible cyclic definition)
hutton.py:7: error: Cannot resolve name "HuttonRazor" (possible cyclic definition)

Which is bitterly upsetting, after having read:

• the typing.ForwardRef docs,
• StackOverflow hits for the error message,
• the mypy FAQ (doesn't CtrlF cyclic anything).

The error message of v0.710 was much better:

hutton.py:5: error: Recursive types not fully supported yet, nested types replaced with "Any"

To be explicit: my expectation is no error. I'm following the typing module doc (and ergo, PEP 484).

I'd also searched among GitHub issues off course. #7069 is closed as "known limitation". #731 is the canonical f̶i̶v̶e̶-̶y̶e̶a̶r̶-̶o̶l̶d̶ issue where actual discussion & development of recursive types support happen. I can remember looking at it ~2 years ago, still open today.

The special prize goes to #6740 — "Stop saying mypy is beta software?". Haha, yes. Nice joke. Save it for tomorrow.

[emmatyping]

Haha, yes. Nice joke.

There is no need to be rude. Consider this a warning to not be rude further.

Just because mypy doesn't support what you want doesn't mean it isn't ready to be used in production. Regardless this is a duplicate so I am closing.