set mypy to target 3.8 by default

Author: DetachHead

.github/workflows/check.yaml

@@ -32,7 +32,7 @@ jobs:
         if: steps.cache.outputs.cache-hit == 'true'
         run: timeout 10s poetry run pip --version || rm -rf .venv
       - run: poetry install
-      - run: poetry run mypy -p basedtyping -p tests
+      - run: poetry run mypy -p basedtyping -p tests --python-version ${{ matrix.python-version }}
       - run: poetry run pytest tests/
 
   lint:

pyproject.toml

@@ -23,6 +23,7 @@ build-backend = "poetry.core.masonry.api"
 requires = ["poetry-core>=1.0.8"]
 
 [tool.mypy]
+python_version = 3.8
 pretty = true
 show_error_context = true