Fix false positive for @override function parameters

CHANGELOG.md

@@ -1,6 +1,7 @@
 # 2.17 (unreleased)
 
 * Add support for Python 3.15 and drop 3.9 (Hugo van Kemenade, #416).
+* Fix false positive for `@override` function parameters (#410).
 
 # 2.16 (2026-03-25)
 

tests/test_scavenging.py

@@ -882,3 +882,118 @@ class Color(Enum):
 
     check(v.unused_classes, [])
     check(v.unused_vars, ["BLUE"])
+
+
+def test_override_typing(v):
+    v.scan(
+        """\
+from typing import override
+
+class A():
+    def my_func(self, a: int, b: int, c: int):
+        return a + b + c
+
+class B(A):
+    @override
+    def my_func(self, a, b, c):
+        return a - b
+"""
+    )
+    check(v.defined_vars, ["a", "b", "c"])
+    check(v.used_names, ["A", "a", "b", "c", "int", "override"])
+    check(v.unused_vars, [])
+
+
+def test_override_typing_extensions(v):
+    v.scan(
+        """\
+from typing_extensions import override
+
+class A():
+    def my_func(self, a: int, b: int, c: int):
+        return a + b + c
+
+class B(A):
+    @override
+    def my_func(self, a, b, c):
+        return a - b
+"""
+    )
+    check(v.defined_vars, ["a", "b", "c"])
+    check(v.used_names, ["A", "a", "b", "c", "int", "override"])
+    check(v.unused_vars, [])
+
+
+def test_override_async(v):
+    v.scan(
+        """\
+from typing import override
+
+class A():
+    async def my_func(self, a: int, b: int, c: int):
+        return a + b + c
+
+class B(A):
+    @override
+    async def my_func(self, a, b, c):
+        return a - b
+"""
+    )
+    check(v.defined_vars, ["a", "b", "c"])
+    check(v.used_names, ["A", "a", "b", "c", "int", "override"])
+    check(v.unused_vars, [])
+
+
+def test_override_nested_function(v):
+    v.scan(
+        """\
+from typing import override
+
+class A():
+    def my_func(self, a: int, b: int, c: int):
+        return a + b + c
+
+class B(A):
+    @override
+    def my_func(self, a, b, c):
+        def inner(x, y):
+            return x
+        return a - b
+"""
+    )
+    check(v.defined_vars, ["a", "b", "c", "x", "y"])
+    check(v.used_names, ["A", "a", "b", "c", "int", "override", "x"])
+    check(v.unused_vars, ["y"])
+
+
+def test_override_with_args_kwargs(v):
+    v.scan(
+        """\
+from typing import override
+
+class A():
+    def my_func(self, *args, **kwargs):
+        return args
+
+class B(A):
+    @override
+    def my_func(self, *args, **kwargs):
+        return None
+"""
+    )
+    check(v.defined_vars, ["args", "kwargs"])
+    check(v.used_names, ["A", "args", "override"])
+    check(v.unused_vars, ["kwargs"])
+
+
+def test_no_override_still_flags(v):
+    v.scan(
+        """\
+class A():
+    def my_func(self, a, b, c):
+        return a - b
+"""
+    )
+    check(v.defined_vars, ["a", "b", "c"])
+    check(v.used_names, ["a", "b"])
+    check(v.unused_vars, ["c"])

vulture/core.py

@@ -216,6 +216,7 @@ def get_list(typ):
         self.code = []
         self.exit_code = ExitCode.NoDeadCode
         self.noqa_lines = {}
+        self._override_depth = 0
 
         report = partial(
             self._define,
@@ -470,7 +471,8 @@ def _define_variable(self, name, node, confidence=DEFAULT_CONFIDENCE):
 
     def visit_arg(self, node):
         """Function argument"""
-        self._define_variable(node.arg, node, confidence=100)
+        if self._override_depth == 0:
+            self._define_variable(node.arg, node, confidence=100)
 
     def visit_AsyncFunctionDef(self, node):
         return self.visit_FunctionDef(node)
@@ -547,6 +549,25 @@ def _is_locals_call(node):
             and not node.keywords
         )
 
+    @staticmethod
+    def _has_override_decorator(node):
+        """Check if a function has the @override decorator.
+
+        Supports:
+        - @override
+        - @typing.override
+        - @typing_extensions.override
+        """
+        for decorator in node.decorator_list:
+            name = utils.get_decorator_name(decorator)
+            if name in (
+                "@override",
+                "@typing.override",
+                "@typing_extensions.override",
+            ):
+                return True
+        return False
+
     def visit_ClassDef(self, node):
         for decorator in node.decorator_list:
             if _match(
@@ -623,9 +644,23 @@ def visit_MatchClass(self, node):
             self.used_names.add(kwd_attr)
 
     def visit(self, node):
+        # For function definitions, save and restore the override depth.
+        # This ensures inner functions don't inherit the parent's override state.
+        saved_override_depth = None
+        if isinstance(node, (ast.FunctionDef, ast.AsyncFunctionDef)):
+            saved_override_depth = self._override_depth
+            if self._has_override_decorator(node):
+                self._override_depth = 1
+            else:
+                self._override_depth = 0
+
         # Visit children nodes first to allow recursive reachability analysis.
         self.generic_visit(node)
 
+        # Restore override depth after visiting children.
+        if saved_override_depth is not None:
+            self._override_depth = saved_override_depth
+
         self.reachability.visit(node)
 
         method = "visit_" + node.__class__.__name__