升级pdm到2.20.0后，执行pdm add --dev mypy时报错了：

INFO: Adding group dev to lockfile
Adding packages to dev dev-dependencies: pytest, pdm, ruff, click, mypy
⠋ 0:00:00 Resolving dependencies
See /Users/mac10.12/Library/Logs/pdm/pdm-lock-aew5ui_n.log for detailed debug log.
[TypeError]: type 'AbstractProvider' is not subscriptable
WARNING: Add '-v' to see the detailed traceback

根据错误提示，打开/Users/mac10.12/Library/Logs/pdm/pdm-lock-aew5ui_n.log文件，发现报错的是:

pdm.termui: Error occurs
Traceback (most recent call last):
  File "/Users/mac10.12/.local/pipx/venvs/pdm/lib/python3.11/site-packages/pdm/termui.py", line 260, in logging
    yield logger
  File "/Users/mac10.12/.local/pipx/venvs/pdm/lib/python3.11/site-packages/pdm/cli/actions.py", line 122, in do_lock
    resolver = resolver_class(
               ^^^^^^^^^^^^^^^
  File "<string>", line 13, in __init__
  File "/Users/mac10.12/.local/pipx/venvs/pdm/lib/python3.11/site-packages/pdm/resolver/resolvelib.py", line 30, in __post_init__
    provider = self.project.get_provider(
               ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/mac10.12/.local/pipx/venvs/pdm/lib/python3.11/site-packages/pdm/project/core.py", line 552, in get_provider
    from pdm.resolver.providers import get_provider
  File "/Users/mac10.12/.local/pipx/venvs/pdm/lib/python3.11/site-packages/pdm/resolver/providers.py", line 49, in <module>
    class BaseProvider(AbstractProvider[Requirement, Candidate, str]):
                       ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: type 'AbstractProvider' is not subscriptable

vi /Users/mac10.12/.local/pipx/venvs/pdm/lib/python3.11/site-packages/pdm/resolver/providers.py打开该文件，发现报错的是resolvelib库的AbstractProvider，猜测是该库没有升级到最新版导致的。

于是执行如下命令，升级该库，问题就解决了：

cd ~/.local/pipx/venvs/pdm # 注：我的pdm是用pipx安装的
source bin/activate
python -m pip install -U resolvelib
# Uninstalling resolvelib-1.0.1
# Successfully installed resolvelib-1.1.0
deactivate
cd -
pdm add --dev ruff