[bugfix] Fix unannotated parameter case

Author: ftnext

src/kotoha/core.py

@@ -1,5 +1,4 @@
 import ast
-from typing import cast
 
 KTH000 = (
     "KTH000 "
@@ -14,9 +13,15 @@ def __init__(self) -> None:
         self.errors: list[tuple[int, int, str]] = []
 
     def visit_arg(self, node: ast.arg) -> None:
-        annotation = cast(ast.Constant, node.annotation)
-        if annotation.value.id in {"list", "dict", "set", "tuple"}:
-            self.errors.append((node.lineno, node.col_offset, KTH000))
+        if node.annotation is not None:
+            annotation: ast.expr = node.annotation
+            if hasattr(annotation, "value") and annotation.value.id in {
+                "list",
+                "dict",
+                "set",
+                "tuple",
+            }:
+                self.errors.append((node.lineno, node.col_offset, KTH000))
         self.generic_visit(node)
 
 

tests/test_core.py

@@ -29,3 +29,16 @@ def plus_one_ok(numbers: Iterable[int]) -> list[int]:
         assert len(checker.errors) == 1
         assert checker.errors[0] == (6, 16, ANY)
         assert checker.errors[0][2].startswith("KTH000")
+
+    def test_KTH000_none_annotation(self):
+        code = dedent(
+            """\
+        def plus_one_ng(numbers: list[int], dummy) -> list[int]:
+            return [n + 1 for n in numbers]
+        """
+        )
+
+        checker = ArgumentConcreteTypeHintChecker()
+        checker.visit(ast.parse(code))
+
+        assert len(checker.errors) == 1