Update to mypy 1.16 and add typecheck to CI

Author: fkleon

.github/workflows/test.yml

@@ -18,5 +18,7 @@ jobs:
         run: make .venv
       - name: Run lint
         run: make lint
+      - name: Run typecheck
+        run: make typecheck
       - name: Run tests
         run: make test

pyproject.toml

@@ -28,7 +28,7 @@ dependencies = [
 debug = ["bluetooth-data-tools ~= 1.15"]
 dev = [
     "async-timer ~= 1.1.6",
-    "mypy ~= 1.15.0",
+    "mypy ~= 1.16.0",
     "pytest ~= 8.3",
     "pytest-asyncio ~= 1.0.0",
     "python-dbusmock ~= 0.34.3",

src/pb_ble/messages.py

@@ -102,9 +102,14 @@ def unpack_pnp_id(data: bytes) -> Tuple[Literal["BT", "USB"], int, int, int]:
     :return: Tuple containing the vendor ID type (`BT` or `USB`), the vendor
         ID, the product ID and the product revision.
     """
+    vid_type: int
+    vid: int
+    pid: int
+    rev: int
+
     vid_type, vid, pid, rev = unpack("<BHHH", data)
-    vid_type = "BT" if vid_type else "USB"
-    return vid_type, vid, pid, rev
+
+    return "BT" if vid_type else "USB", vid, pid, rev
 
 
 def pack_pnp_id(