PEP 585 runtime exceptions not recognized

[cdce8p]

Environment data

• Language Server version: 2021.2.4
• OS and version: MacOS 10.15.7
• Python version: 3.8.8
• typeCheckingMode: strict

Expected behaviour

The following examples should be invalid without from __future__ import annotations in Python 3.7 and 3.8.

import collections
import collections.abc
import contextlib
import re

var: collections.defaultdict[int, str]
var2: collections.abc.Iterable[int]  # and every other type from `collections.abc` (except `Hashable` and `Sized`)
var3: contextlib.AbstractContextManager[int]
var4: contextlib.AbstractAsyncContextManager[int]
var5: re.Pattern[str]
var6: re.Match[str]

https://docs.python.org/3/library/typing.html#corresponding-to-other-types-in-collections-abc

Actual behaviour

Pylance doesn't infer them as errors.
Interestingly collections.OrderedDict[int, str], ChainMap, Counter and deque are recognized correctly.

[erictraut]

Thanks for the suggestion.

I was able to address this for collections.defaultdict, but I can't do anything about the others because the stdlib type stubs simply alias the types in typing.pyi. From the perspective of Pyright, collections.abc.Iterable is simply an alias for typing.Iterable, so it can't differentiate between the two. If you would like to submit changes to typeshed's stubs so these become distinct types, I could easily add support.

The fix for collections.defaultdict will be in the next release.

[jakebailey]

This issue has been fixed in version 2021.3.0, which we've just released. You can find the changelog here: https://github.com/microsoft/pylance-release/blob/main/CHANGELOG.md#202130-3-march-2021