MAINT: Use mypy recursive type support

[j-t-1]

In mypy>=1.7 recursive type support is built-in.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.36%. Comparing base (27edc06) to head (050a09e).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2898   +/-   ##
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  Coverage   96.36%   96.36%           
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  Files          52       52           
  Lines        8751     8751           
  Branches     1593     1593           
=======================================
  Hits         8433     8433           
  Misses        190      190           
  Partials      128      128           

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[j-t-1]

Is this failing because mypy==1.4.1 is being used in ci.txt?

Fixable if pip-compile requirements/ci.in is run with Python 3.8?

[stefan6419846]

These are docs build issues, not related to mypy. They might be fixed with a more recent sphinx version, but this requires further updates to other packages and the configuration file: #2573 (comment) I had planned to do this in the summer, but have been quite busy with more important tasks. I will try to find some time in the next weeks.

[stefan6419846]

Apparently Sphinx does not like recursive types. Does delayed evaluation with __future__.annotations work? Otherwise, we might have to look for a corresponding upstream issue or report one ourselves.

[j-t-1]

Thanks @stefan6419846. Upstream solution may be simplest, although is low priority.