context manager work properly

[KotlinIsland]

• resolves #522
• resolves #519

[github-actions[bot]]

Diff from mypy_primer, showing the effect of this PR on open source code:

Tanjun (https://github.com/FasterSpeeding/Tanjun)
-   File "/tmp/mypy_primer/old_mypy/venv/bin/mypy", line 8, in <module>
+   File "/tmp/mypy_primer/new_mypy/venv/bin/mypy", line 8, in <module>
-   File "/tmp/mypy_primer/old_mypy/venv/lib/python3.10/site-packages/mypy/__main__.py", line 15, in console_entry
+   File "/tmp/mypy_primer/new_mypy/venv/lib/python3.10/site-packages/mypy/__main__.py", line 15, in console_entry
-   File "/tmp/mypy_primer/old_mypy/venv/lib/python3.10/site-packages/mypy/main.py", line 95, in main
+   File "/tmp/mypy_primer/new_mypy/venv/lib/python3.10/site-packages/mypy/main.py", line 95, in main
-   File "/tmp/mypy_primer/old_mypy/venv/lib/python3.10/site-packages/mypy/main.py", line 199, in run_build
+   File "/tmp/mypy_primer/new_mypy/venv/lib/python3.10/site-packages/mypy/main.py", line 199, in run_build
-   File "/tmp/mypy_primer/old_mypy/venv/lib/python3.10/site-packages/mypy/build.py", line 200, in build
+   File "/tmp/mypy_primer/new_mypy/venv/lib/python3.10/site-packages/mypy/build.py", line 200, in build
-   File "/tmp/mypy_primer/old_mypy/venv/lib/python3.10/site-packages/mypy/build.py", line 276, in _build
+   File "/tmp/mypy_primer/new_mypy/venv/lib/python3.10/site-packages/mypy/build.py", line 276, in _build
-   File "/tmp/mypy_primer/old_mypy/venv/lib/python3.10/site-packages/mypy/build.py", line 3063, in dispatch
+   File "/tmp/mypy_primer/new_mypy/venv/lib/python3.10/site-packages/mypy/build.py", line 3063, in dispatch
-   File "/tmp/mypy_primer/old_mypy/venv/lib/python3.10/site-packages/mypy/build.py", line 3463, in process_graph
+   File "/tmp/mypy_primer/new_mypy/venv/lib/python3.10/site-packages/mypy/build.py", line 3463, in process_graph
-   File "/tmp/mypy_primer/old_mypy/venv/lib/python3.10/site-packages/mypy/build.py", line 3586, in process_stale_scc
+   File "/tmp/mypy_primer/new_mypy/venv/lib/python3.10/site-packages/mypy/build.py", line 3586, in process_stale_scc
-   File "/tmp/mypy_primer/old_mypy/venv/lib/python3.10/site-packages/mypy/build.py", line 2623, in write_cache
+   File "/tmp/mypy_primer/new_mypy/venv/lib/python3.10/site-packages/mypy/build.py", line 2623, in write_cache
-   File "/tmp/mypy_primer/old_mypy/venv/lib/python3.10/site-packages/mypy/nodes.py", line 389, in serialize
+   File "/tmp/mypy_primer/new_mypy/venv/lib/python3.10/site-packages/mypy/nodes.py", line 389, in serialize
-   File "/tmp/mypy_primer/old_mypy/venv/lib/python3.10/site-packages/mypy/nodes.py", line 3939, in serialize
+   File "/tmp/mypy_primer/new_mypy/venv/lib/python3.10/site-packages/mypy/nodes.py", line 3939, in serialize
-   File "/tmp/mypy_primer/old_mypy/venv/lib/python3.10/site-packages/mypy/nodes.py", line 3876, in serialize
+   File "/tmp/mypy_primer/new_mypy/venv/lib/python3.10/site-packages/mypy/nodes.py", line 3876, in serialize
-   File "/tmp/mypy_primer/old_mypy/venv/lib/python3.10/site-packages/mypy/nodes.py", line 3613, in serialize
+   File "/tmp/mypy_primer/new_mypy/venv/lib/python3.10/site-packages/mypy/nodes.py", line 3613, in serialize
-   File "/tmp/mypy_primer/old_mypy/venv/lib/python3.10/site-packages/mypy/nodes.py", line 3613, in <listcomp>
+   File "/tmp/mypy_primer/new_mypy/venv/lib/python3.10/site-packages/mypy/nodes.py", line 3613, in <listcomp>
-   File "/tmp/mypy_primer/old_mypy/venv/lib/python3.10/site-packages/mypy/types.py", line 662, in serialize
+   File "/tmp/mypy_primer/new_mypy/venv/lib/python3.10/site-packages/mypy/types.py", line 662, in serialize
-   File "/tmp/mypy_primer/old_mypy/venv/lib/python3.10/site-packages/mypy/types.py", line 3161, in serialize
+   File "/tmp/mypy_primer/new_mypy/venv/lib/python3.10/site-packages/mypy/types.py", line 3161, in serialize