Fix crash due to runtime import of typing_extensions

[gschaffner]

hi!

#2502 added a runtime dependency on typing_extensions but did not update the packaging config to specify this dependency.

presently no runtime features of typing_extensions are being used, so it does not need to be a dependency at runtime.

(I have not included a changelog entry here since #2502 did not either and the bug this fixes was never user-facing.)

[codecov]

Codecov Report

Merging #2507 (0da0068) into master (ec32bb8) will decrease coverage by 4.47%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2507      +/-   ##
==========================================
- Coverage   97.98%   93.51%   -4.48%     
==========================================
  Files         118      118              
  Lines       16327    16327              
  Branches     3156     3156              
==========================================
- Hits        15998    15268     -730     
- Misses        266      954     +688     
- Partials       63      105      +42     

Impacted Files	Coverage Δ
trio/_unix_pipes.py	97.84% <100.00%> (-2.16%)	⬇️
trio/_windows_pipes.py	0.00% <0.00%> (-100.00%)	⬇️
trio/_wait_for_object.py	0.00% <0.00%> (-100.00%)	⬇️
trio/_core/_windows_cffi.py	0.00% <0.00%> (-100.00%)	⬇️
trio/_subprocess_platform/windows.py	0.00% <0.00%> (-100.00%)	⬇️
trio/_core/_io_windows.py	0.00% <0.00%> (-98.77%)	⬇️
trio/tests/test_wait_for_object.py	10.37% <0.00%> (-89.63%)	⬇️
trio/_core/tests/test_windows.py	17.82% <0.00%> (-82.18%)	⬇️
trio/tests/test_windows_pipes.py	26.58% <0.00%> (-73.42%)	⬇️
trio/_subprocess_platform/__init__.py	62.85% <0.00%> (-31.43%)	⬇️
... and 20 more

[gschaffner]

the test suite timeout on CPython 3.9 on Windows x86-64 seems unrelated and likely just needs a rerun

[pquentin]

Thanks!

[A5rocks]

Looks good! Why didn't our test suite catch this? Do we need to separate out typing dependencies (mypy depends on typing_extensions) and test dependencies?

[gschaffner]

yep, looks like it. see

trio/test-requirements.txt

Lines 124 to 127 in 4e7f21e

	typing-extensions==4.4.0 ; implementation_name == "cpython"
	# via
	# -r test-requirements.in
	# mypy

while in this case this bug would have been automatically caught if MyPy was not in the test dependencies, the same bug can always still go uncaught in the future if a package required for testing starts depending on typing_extensions.