Restrict `builtin-attribute-shadowing` to actual shadowed references (#9462)

## Summary

This PR attempts to improve `builtin-attribute-shadowing` (`A003`), a
rule which has been repeatedly criticized, but _does_ have value (just
not in the current form).

Historically, this rule would flag cases like:

```python
class Class:
    id: int
```

This led to an increasing number of exceptions and special-cases to the
rule over time to try and improve it's specificity (e.g., ignore
`TypedDict`, ignore `@override`).

The crux of the issue is that given the above, referencing `id` will
never resolve to `Class.id`, so the shadowing is actually fine. There's
one exception, however:

```python
class Class:
    id: int

    def do_thing() -> id:
        pass
```

Here, `id` actually resolves to the `id` attribute on the class, not the
`id` builtin.

So this PR completely reworks the rule around this _much_ more targeted
case, which will almost always be a mistake: when you reference a class
member from within the class, and that member shadows a builtin.

Closes https://github.com/astral-sh/ruff/issues/6524.

Closes https://github.com/astral-sh/ruff/issues/7806.

crates/ruff_linter/resources/test/fixtures/flake8_builtins/A003.py

@@ -8,46 +8,14 @@ class MyClass:
         self.id = 10
         self.dir = "."
 
-    def str(self):
-        pass
-
-
-from typing import TypedDict
-
-
-class MyClass(TypedDict):
-    id: int
-
-
-from threading import Event
-
-
-class CustomEvent(Event):
-    def set(self) -> None:
-        ...
-
-    def str(self) -> None:
-        ...
-
-
-from logging import Filter, LogRecord
-
-
-class CustomFilter(Filter):
-    def filter(self, record: LogRecord) -> bool:
-        ...
-
-    def str(self) -> None:
-        ...
-
-
-from typing_extensions import override
-
-
-class MyClass:
-    @override
-    def str(self):
-        pass
-
     def int(self):
         pass
+
+    def str(self):
+        pass
+
+    def method_usage(self) -> str:
+        pass
+
+    def attribute_usage(self) -> id:
+        pass

crates/ruff_linter/src/checkers/ast/analyze/deferred_scopes.rs

@@ -7,7 +7,8 @@ use crate::checkers::ast::Checker;
 use crate::codes::Rule;
 use crate::fix;
 use crate::rules::{
-    flake8_pyi, flake8_type_checking, flake8_unused_arguments, pyflakes, pylint, ruff,
+    flake8_builtins, flake8_pyi, flake8_type_checking, flake8_unused_arguments, pyflakes, pylint,
+    ruff,
 };
 
 /// Run lint rules over all deferred scopes in the [`SemanticModel`].
@@ -27,6 +28,7 @@ pub(crate) fn deferred_scopes(checker: &mut Checker) {
         Rule::UndefinedLocal,
         Rule::UnusedAnnotation,
         Rule::UnusedClassMethodArgument,
+        Rule::BuiltinAttributeShadowing,
         Rule::UnusedFunctionArgument,
         Rule::UnusedImport,
         Rule::UnusedLambdaArgument,
@@ -297,6 +299,18 @@ pub(crate) fn deferred_scopes(checker: &mut Checker) {
             ruff::rules::asyncio_dangling_binding(scope, &checker.semantic, &mut diagnostics);
         }
 
+        if let Some(class_def) = scope.kind.as_class() {
+            if checker.enabled(Rule::BuiltinAttributeShadowing) {
+                flake8_builtins::rules::builtin_attribute_shadowing(
+                    checker,
+                    scope_id,
+                    scope,
+                    class_def,
+                    &mut diagnostics,
+                );
+            }
+        }
+
         if matches!(scope.kind, ScopeKind::Function(_) | ScopeKind::Lambda(_)) {
             if checker.enabled(Rule::UnusedVariable) {
                 pyflakes::rules::unused_variable(checker, scope, &mut diagnostics);

crates/ruff_linter/src/checkers/ast/analyze/expression.rs

@@ -242,13 +242,7 @@ pub(crate) fn expression(expr: &Expr, checker: &mut Checker) {
                             checker.diagnostics.push(diagnostic);
                         }
                     }
-                    if let ScopeKind::Class(class_def) = checker.semantic.current_scope().kind {
+                    if !checker.semantic.current_scope().kind.is_class() {
-                        if checker.enabled(Rule::BuiltinAttributeShadowing) {
-                            flake8_builtins::rules::builtin_attribute_shadowing(
-                                checker, class_def, id, *range,
-                            );
-                        }
-                    } else {
                         if checker.enabled(Rule::BuiltinVariableShadowing) {
                             flake8_builtins::rules::builtin_variable_shadowing(checker, id, *range);
                         }

crates/ruff_linter/src/checkers/ast/analyze/statement.rs

@@ -347,17 +347,7 @@ pub(crate) fn statement(stmt: &Stmt, checker: &mut Checker) {
             if checker.enabled(Rule::FStringDocstring) {
                 flake8_bugbear::rules::f_string_docstring(checker, body);
             }
-            if let ScopeKind::Class(class_def) = checker.semantic.current_scope().kind {
+            if !checker.semantic.current_scope().kind.is_class() {
-                if checker.enabled(Rule::BuiltinAttributeShadowing) {
-                    flake8_builtins::rules::builtin_method_shadowing(
-                        checker,
-                        class_def,
-                        name,
-                        decorator_list,
-                        name.range(),
-                    );
-                }
-            } else {
                 if checker.enabled(Rule::BuiltinVariableShadowing) {
                     flake8_builtins::rules::builtin_variable_shadowing(checker, name, name.range());
                 }

crates/ruff_linter/src/rules/flake8_builtins/rules/builtin_attribute_shadowing.rs

@@ -1,11 +1,10 @@
-use ruff_python_ast as ast;
-use ruff_python_ast::{Arguments, Decorator};
-use ruff_text_size::TextRange;
-
 use ruff_diagnostics::Diagnostic;
 use ruff_diagnostics::Violation;
 use ruff_macros::{derive_message_formats, violation};
-use ruff_python_semantic::SemanticModel;
+use ruff_python_ast as ast;
+use ruff_python_semantic::{BindingKind, Scope, ScopeId};
+use ruff_source_file::SourceRow;
+use ruff_text_size::Ranged;
 
 use crate::checkers::ast::Checker;
 use crate::rules::flake8_builtins::helpers::shadows_builtin;
@@ -20,6 +19,23 @@ use crate::rules::flake8_builtins::helpers::shadows_builtin;
 /// non-obvious errors, as readers may mistake the attribute for the
 /// builtin and vice versa.
 ///
+/// Since methods and class attributes typically cannot be referenced directly
+/// from outside the class scope, this rule only applies to those methods
+/// and attributes that both shadow a builtin _and_ are referenced from within
+/// the class scope, as in the following example, where the `list[int]` return
+/// type annotation resolves to the `list` method, rather than the builtin:
+///
+/// ```python
+/// class Class:
+///     @staticmethod
+///     def list() -> None:
+///         pass
+///
+///     @staticmethod
+///     def repeat(value: int, times: int) -> list[int]:
+///         return [value] * times
+/// ```
+///
 /// Builtins can be marked as exceptions to this rule via the
 /// [`flake8-builtins.builtins-ignorelist`] configuration option, or
 /// converted to the appropriate dunder method. Methods decorated with
@@ -28,135 +44,112 @@ use crate::rules::flake8_builtins::helpers::shadows_builtin;
 ///
 /// ## Example
 /// ```python
-/// class Shadow:
+/// class Class:
-///     def int():
+///     @staticmethod
-///         return 0
+///     def list() -> None:
-/// ```
+///         pass
 ///
-/// Use instead:
+///     @staticmethod
-/// ```python
+///     def repeat(value: int, times: int) -> list[int]:
-/// class Shadow:
+///         return [value] * times
-///     def to_int():
-///         return 0
-/// ```
-///
-/// Or:
-/// ```python
-/// class Shadow:
-///     # Callable as `int(shadow)`
-///     def __int__():
-///         return 0
 /// ```
 ///
 /// ## Options
 /// - `flake8-builtins.builtins-ignorelist`
-///
-/// ## References
-/// - [_Is it bad practice to use a built-in function name as an attribute or method identifier?_](https://stackoverflow.com/questions/9109333/is-it-bad-practice-to-use-a-built-in-function-name-as-an-attribute-or-method-ide)
-/// - [_Why is it a bad idea to name a variable `id` in Python?_](https://stackoverflow.com/questions/77552/id-is-a-bad-variable-name-in-python)
 #[violation]
 pub struct BuiltinAttributeShadowing {
+    kind: Kind,
     name: String,
+    row: SourceRow,
 }
 
 impl Violation for BuiltinAttributeShadowing {
     #[derive_message_formats]
     fn message(&self) -> String {
-        let BuiltinAttributeShadowing { name } = self;
+        let BuiltinAttributeShadowing { kind, name, row } = self;
-        format!("Class attribute `{name}` is shadowing a Python builtin")
+        match kind {
+            Kind::Attribute => {
+                format!("Python builtin is shadowed by class attribute `{name}` from {row}")
+            }
+            Kind::Method => {
+                format!("Python builtin is shadowed by method `{name}` from {row}")
+            }
+        }
     }
 }
 
 /// A003
 pub(crate) fn builtin_attribute_shadowing(
-    checker: &mut Checker,
+    checker: &Checker,
+    scope_id: ScopeId,
+    scope: &Scope,
     class_def: &ast::StmtClassDef,
-    name: &str,
+    diagnostics: &mut Vec<Diagnostic>,
-    range: TextRange,
 ) {
-    if shadows_builtin(
+    for (name, binding_id) in scope.all_bindings() {
-        name,
+        let binding = checker.semantic().binding(binding_id);
-        &checker.settings.flake8_builtins.builtins_ignorelist,
-        checker.source_type,
-    ) {
-        // Ignore shadowing within `TypedDict` definitions, since these are only accessible through
-        // subscripting and not through attribute access.
-        if class_def
-            .bases()
-            .iter()
-            .any(|base| checker.semantic().match_typing_expr(base, "TypedDict"))
-        {
-            return;
-        }
 
-        checker.diagnostics.push(Diagnostic::new(
+        // We only care about methods and attributes.
-            BuiltinAttributeShadowing {
+        let kind = match binding.kind {
-                name: name.to_string(),
+            BindingKind::Assignment | BindingKind::Annotation => Kind::Attribute,
-            },
+            BindingKind::FunctionDefinition(_) => Kind::Method,
-            range,
+            _ => continue,
-        ));
+        };
+
+        if shadows_builtin(
+            name,
+            &checker.settings.flake8_builtins.builtins_ignorelist,
+            checker.source_type,
+        ) {
+            // Ignore explicit overrides.
+            if class_def.decorator_list.iter().any(|decorator| {
+                checker
+                    .semantic()
+                    .match_typing_expr(&decorator.expression, "override")
+            }) {
+                return;
+            }
+
+            // Class scopes are special, in that you can only reference a binding defined in a
+            // class scope from within the class scope itself. As such, we can safely ignore
+            // methods that weren't referenced from within the class scope. In other words, we're
+            // only trying to identify shadowing as in:
+            // ```python
+            // class Class:
+            //     @staticmethod
+            //     def list() -> None:
+            //         pass
+            //
+            //     @staticmethod
+            //     def repeat(value: int, times: int) -> list[int]:
+            //         return [value] * times
+            // ```
+            for reference in binding
+                .references
+                .iter()
+                .map(|reference_id| checker.semantic().reference(*reference_id))
+                .filter(|reference| {
+                    checker
+                        .semantic()
+                        .first_non_type_parent_scope_id(reference.scope_id())
+                        == Some(scope_id)
+                })
+            {
+                diagnostics.push(Diagnostic::new(
+                    BuiltinAttributeShadowing {
+                        kind,
+                        name: name.to_string(),
+                        row: checker.compute_source_row(binding.start()),
+                    },
+                    reference.range(),
+                ));
+            }
+        }
     }
 }
 
-/// A003
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
-pub(crate) fn builtin_method_shadowing(
+enum Kind {
-    checker: &mut Checker,
+    Attribute,
-    class_def: &ast::StmtClassDef,
+    Method,
-    name: &str,
-    decorator_list: &[Decorator],
-    range: TextRange,
-) {
-    if shadows_builtin(
-        name,
-        &checker.settings.flake8_builtins.builtins_ignorelist,
-        checker.source_type,
-    ) {
-        // Ignore some standard-library methods. Ideally, we'd ignore all overridden methods, since
-        // those should be flagged on the superclass, but that's more difficult.
-        if is_standard_library_override(name, class_def, checker.semantic()) {
-            return;
-        }
-
-        // Ignore explicit overrides.
-        if decorator_list.iter().any(|decorator| {
-            checker
-                .semantic()
-                .match_typing_expr(&decorator.expression, "override")
-        }) {
-            return;
-        }
-
-        checker.diagnostics.push(Diagnostic::new(
-            BuiltinAttributeShadowing {
-                name: name.to_string(),
-            },
-            range,
-        ));
-    }
-}
-
-/// Return `true` if an attribute appears to be an override of a standard-library method.
-fn is_standard_library_override(
-    name: &str,
-    class_def: &ast::StmtClassDef,
-    semantic: &SemanticModel,
-) -> bool {
-    let Some(Arguments { args: bases, .. }) = class_def.arguments.as_deref() else {
-        return false;
-    };
-    match name {
-        // Ex) `Event.set`
-        "set" => bases.iter().any(|base| {
-            semantic
-                .resolve_call_path(base)
-                .is_some_and(|call_path| matches!(call_path.as_slice(), ["threading", "Event"]))
-        }),
-        // Ex) `Filter.filter`
-        "filter" => bases.iter().any(|base| {
-            semantic
-                .resolve_call_path(base)
-                .is_some_and(|call_path| matches!(call_path.as_slice(), ["logging", "Filter"]))
-        }),
-        _ => false,
-    }
 }

crates/ruff_linter/src/rules/flake8_builtins/snapshots/ruff_linter__rules__flake8_builtins__tests__A003_A003.py.snap

@@ -1,68 +1,22 @@
 ---
 source: crates/ruff_linter/src/rules/flake8_builtins/mod.rs
 ---
-A003.py:2:5: A003 Class attribute `ImportError` is shadowing a Python builtin
+A003.py:17:31: A003 Python builtin is shadowed by method `str` from line 14
-  |
-1 | class MyClass:
-2 |     ImportError = 4
-  |     ^^^^^^^^^^^ A003
-3 |     id: int
-4 |     dir = "/"
-  |
-
-A003.py:3:5: A003 Class attribute `id` is shadowing a Python builtin
-  |
-1 | class MyClass:
-2 |     ImportError = 4
-3 |     id: int
-  |     ^^ A003
-4 |     dir = "/"
-  |
-
-A003.py:4:5: A003 Class attribute `dir` is shadowing a Python builtin
-  |
-2 |     ImportError = 4
-3 |     id: int
-4 |     dir = "/"
-  |     ^^^ A003
-5 | 
-6 |     def __init__(self):
-  |
-
-A003.py:11:9: A003 Class attribute `str` is shadowing a Python builtin
    |
- 9 |         self.dir = "."
+15 |         pass
-10 | 
+16 | 
-11 |     def str(self):
+17 |     def method_usage(self) -> str:
-   |         ^^^ A003
+   |                               ^^^ A003
-12 |         pass
+18 |         pass
    |
 
-A003.py:29:9: A003 Class attribute `str` is shadowing a Python builtin
+A003.py:20:34: A003 Python builtin is shadowed by class attribute `id` from line 3
    |
-27 |         ...
+18 |         pass
-28 | 
+19 | 
-29 |     def str(self) -> None:
+20 |     def attribute_usage(self) -> id:
-   |         ^^^ A003
+   |                                  ^^ A003
-30 |         ...
+21 |         pass
-   |
-
-A003.py:40:9: A003 Class attribute `str` is shadowing a Python builtin
-   |
-38 |         ...
-39 | 
-40 |     def str(self) -> None:
-   |         ^^^ A003
-41 |         ...
-   |
-
-A003.py:52:9: A003 Class attribute `int` is shadowing a Python builtin
-   |
-50 |         pass
-51 | 
-52 |     def int(self):
-   |         ^^^ A003
-53 |         pass
    |
 
 

crates/ruff_linter/src/rules/flake8_builtins/snapshots/ruff_linter__rules__flake8_builtins__tests__A003_A003.py_builtins_ignorelist.snap

@@ -1,49 +1,13 @@
 ---
 source: crates/ruff_linter/src/rules/flake8_builtins/mod.rs
 ---
-A003.py:2:5: A003 Class attribute `ImportError` is shadowing a Python builtin
+A003.py:17:31: A003 Python builtin is shadowed by method `str` from line 14
-  |
-1 | class MyClass:
-2 |     ImportError = 4
-  |     ^^^^^^^^^^^ A003
-3 |     id: int
-4 |     dir = "/"
-  |
-
-A003.py:11:9: A003 Class attribute `str` is shadowing a Python builtin
    |
- 9 |         self.dir = "."
+15 |         pass
-10 | 
+16 | 
-11 |     def str(self):
+17 |     def method_usage(self) -> str:
-   |         ^^^ A003
+   |                               ^^^ A003
-12 |         pass
+18 |         pass
-   |
-
-A003.py:29:9: A003 Class attribute `str` is shadowing a Python builtin
-   |
-27 |         ...
-28 | 
-29 |     def str(self) -> None:
-   |         ^^^ A003
-30 |         ...
-   |
-
-A003.py:40:9: A003 Class attribute `str` is shadowing a Python builtin
-   |
-38 |         ...
-39 | 
-40 |     def str(self) -> None:
-   |         ^^^ A003
-41 |         ...
-   |
-
-A003.py:52:9: A003 Class attribute `int` is shadowing a Python builtin
-   |
-50 |         pass
-51 | 
-52 |     def int(self):
-   |         ^^^ A003
-53 |         pass
    |
 
 

crates/ruff_python_semantic/src/model.rs

@@ -984,6 +984,11 @@ impl<'a> SemanticModel<'a> {
         scope.parent.map(|scope_id| &self.scopes[scope_id])
     }
 
+    /// Returns the ID of the parent of the given [`ScopeId`], if any.
+    pub fn parent_scope_id(&self, scope_id: ScopeId) -> Option<ScopeId> {
+        self.scopes[scope_id].parent
+    }
+
     /// Returns the first parent of the given [`Scope`] that is not of [`ScopeKind::Type`], if any.
     pub fn first_non_type_parent_scope(&self, scope: &Scope) -> Option<&Scope<'a>> {
         let mut current_scope = scope;
@@ -997,6 +1002,19 @@ impl<'a> SemanticModel<'a> {
         None
     }
 
+    /// Returns the first parent of the given [`ScopeId`] that is not of [`ScopeKind::Type`], if any.
+    pub fn first_non_type_parent_scope_id(&self, scope_id: ScopeId) -> Option<ScopeId> {
+        let mut current_scope_id = scope_id;
+        while let Some(parent_id) = self.parent_scope_id(current_scope_id) {
+            if self.scopes[parent_id].kind.is_type() {
+                current_scope_id = parent_id;
+            } else {
+                return Some(parent_id);
+            }
+        }
+        None
+    }
+
     /// Return the [`Stmt`] corresponding to the given [`NodeId`].
     #[inline]
     pub fn node(&self, node_id: NodeId) -> &NodeRef<'a> {