Use mypy developemnt build

Author: moreal

.github/workflows/build.yaml

@@ -27,4 +27,11 @@ jobs:
     - run: |
         python3 -m pip install --upgrade pip
         python3 -m pip install tox tox-gh-actions
+
+        pushd /tmp
+          git clone https://github.com/python/mypy
+          pushd mypy
+            python -m pip install --upgrade .
+          popd
+        popd
     - run: tox

tox.ini

@@ -17,9 +17,9 @@ commands =
 [testenv:mypy]
 basepython = python3
 deps =
-    mypy >= 0.971
+    mypy >= 0.990+dev.d619c783d4713a13083a1a6e8020075948baceb2
 commands =
-    mypy --install-types --non-interactive -p bencodex
+    mypy --install-types --non-interactive -p bencodex --enable-recursive-aliases
 
 [flake8]
 exclude =