Fix type errors reported in CI

Makefile

@@ -28,12 +28,14 @@ $(HATCH_BIN): $(VENV_TARGET)
 
 
 # test suites
-.PHONY: test test-examples test-unit
-test: test-examples test-unit ## run all test suites
+.PHONY: test test-examples test-unit test-types
+test: test-examples test-unit test-types ## run all test suites
 ALL_EXAMPLES := $(wildcard docs/examples/*.py)
 test-examples: $(ALL_EXAMPLES) ## run example code test suite
 .PHONY: $(ALL_EXAMPLES)
 $(ALL_EXAMPLES): $(HATCH_BIN)
 	$(HATCH_CMD) $@
 test-unit: $(VENV_TARGET) ## run unit test suite
 	$(HATCH_CMD) -m unittest discover -s tests
+test-types:
+	$(PYTHON_CMD) -m hatch run types:check

minject/inject_attrs.py

@@ -108,7 +108,7 @@ def inject_field(binding=_T, **attr_field_kwargs) -> Any:
     # declaration. Extract the name of the field.
     field_frame = stack[1]
     name = ""
-    if len(field_frame.code_context) > 0:
+    if field_frame.code_context:
         code = field_frame.code_context[0].strip()
         name_and_type = code.split("=", maxsplit=1)[0].rstrip().lstrip()
         name = name_and_type.split(":", maxsplit=1)[0].rstrip().lstrip()
@@ -122,9 +122,7 @@ def inject_field(binding=_T, **attr_field_kwargs) -> Any:
     # bindings, so double-check that that assumption holds.
     # (If not, our inferred field name is probably wrong too!)
     class_frame = stack[2]
-    if len(class_frame.code_context) < 1 or not class_frame.code_context[0].strip().startswith(
-        "class "
-    ):
+    if not (class_frame.code_context and class_frame.code_context[0].strip().startswith("class ")):
         raise ValueError(
             "Could not find line containing class declaration. Are you calling inject_field properly?"
         )
@@ -158,9 +156,15 @@ def inject_define_inner(cls: Type[_P]) -> Type[_P]:
                 "Could not find line containing class declaration. Are you calling inject_define properly?"
             )
 
+        class_filename = inspect.getsourcefile(cls)
+        if class_filename is None:
+            raise ValueError(
+                "Could not find filename of class declaration. Are you calling inject_define properly?"
+            )
+
         # get bindings to apply to the class
         key = _BindingKey(
-            filename=inspect.getsourcefile(cls),
+            filename=class_filename,
             class_lineno=class_lineno,
         )
         bindings = _key_binding_mapping[key]