CI: add task typecheck that runs pytype

.github/workflows/main.yml

@@ -55,3 +55,41 @@ jobs:
                 pushd examples/
                 python _test_examples.py
                 popd
+    typecheck:
+        name: Static analysis of Python code
+        runs-on: ubuntu-22.04
+        strategy:
+            matrix:
+                python-version: [
+                    '3.10',
+                    ]
+        steps:
+            - uses: actions/checkout@v3
+            - name: Set up Python ${{ matrix.python-version }}
+              uses: actions/setup-python@v4
+              with:
+                  python-version: ${{ matrix.python-version }}
+            - name: Prepare typechecking environment
+              run: |
+                ./.github/workflows/setup_typecheck_env.sh
+            - name: Statically analyze `dd`
+              run: |
+                pytype -k \
+                    dd/*.py \
+                    -x dd/__init__.py
+            - name: Statically analyze setup files
+              run: |
+                pip install -U \
+                    cython \
+                    gitpython
+                pytype -k \
+                    setup.py \
+                    install.py \
+                    # download.py
+            - name: Statically analyze `examples/`
+              run: |
+                pip uninstall -y dd
+                python install.py --yes \
+                    --ignore-requires-python
+                pytype -k \
+                    examples/*.py

.github/workflows/setup_typecheck_env.sh

@@ -0,0 +1,25 @@
+#!/usr/bin/env bash
+
+
+# Prepare for typechecking.
+
+
+set -x
+set -e
+# upgrade build dependencies
+pip install \
+    --ignore-installed \
+    --upgrade \
+        pip \
+        setuptools \
+        wheel
+# install `dd` dependencies
+python setup.py sdist
+pip install \
+    --ignore-requires-python \
+    dist/dd-*.tar.gz
+pip uninstall --yes dd
+# install typechecking tools
+pip install \
+    --upgrade \
+        pytype