Improve handling of __qualname__, __module__, and __class__ (#4512

)

crates/ruff/src/checkers/ast/mod.rs

@@ -4841,13 +4841,6 @@ impl<'a> Checker<'a> {
                         return;
                     }
 
-                    // Allow "__module__" and "__qualname__" in class scopes.
-                    if (id == "__module__" || id == "__qualname__")
-                        && matches!(self.ctx.scope().kind, ScopeKind::Class(..))
-                    {
-                        return;
-                    }
-
                     // Avoid flagging if `NameError` is handled.
                     if self
                         .ctx

crates/ruff/src/rules/pyflakes/mod.rs

@@ -473,6 +473,16 @@ mod tests {
         "#,
             &[Rule::UndefinedName],
         );
+        flakes(
+            r#"
+        def f():
+            __qualname__ = 1
+
+            class Foo:
+                __qualname__
+        "#,
+            &[Rule::UnusedVariable],
+        );
     }
 
     #[test]
@@ -1151,6 +1161,40 @@ mod tests {
         "#,
             &[],
         );
+        flakes(
+            r#"
+        class Test(object):
+            print(__class__.__name__)
+
+            def __init__(self):
+                self.x = 1
+
+        t = Test()
+        "#,
+            &[Rule::UndefinedName],
+        );
+        flakes(
+            r#"
+        class Test(object):
+            X = [__class__ for _ in range(10)]
+
+            def __init__(self):
+                self.x = 1
+
+        t = Test()
+        "#,
+            &[Rule::UndefinedName],
+        );
+        flakes(
+            r#"
+        def f(self):
+            print(__class__.__name__)
+            self.x = 1
+
+        f()
+        "#,
+            &[Rule::UndefinedName],
+        );
     }
 
     /// See: <https://github.com/PyCQA/pyflakes/blob/04ecb0c324ef3b61124e2f80f9e1af6c3a4c7b26/pyflakes/test/test_imports.py>

crates/ruff_python_semantic/src/context.rs

@@ -126,11 +126,19 @@ impl<'a> Context<'a> {
             }
         }
 
+        let mut seen_function = false;
         let mut import_starred = false;
         for (index, scope_id) in self.scopes.ancestor_ids(self.scope_id).enumerate() {
             let scope = &self.scopes[scope_id];
             if scope.kind.is_class() {
-                if symbol == "__class__" {
+                // Allow usages of `__class__` within methods, e.g.:
+                //
+                // ```python
+                // class Foo:
+                //     def __init__(self):
+                //         print(__class__)
+                // ```
+                if seen_function && matches!(symbol, "__class__") {
                     return ResolvedReference::ImplicitGlobal;
                 }
                 if index > 0 {
@@ -162,6 +170,28 @@ impl<'a> Context<'a> {
                 return ResolvedReference::Resolved(scope_id, *binding_id);
             }
 
+            // Allow usages of `__module__` and `__qualname__` within class scopes, e.g.:
+            //
+            // ```python
+            // class Foo:
+            //     print(__qualname__)
+            // ```
+            //
+            // Intentionally defer this check to _after_ the standard `scope.get` logic, so that
+            // we properly attribute reads to overridden class members, e.g.:
+            //
+            // ```python
+            // class Foo:
+            //     __qualname__ = "Bar"
+            //     print(__qualname__)
+            // ```
+            if index == 0 && scope.kind.is_class() {
+                if matches!(symbol, "__module__" | "__qualname__") {
+                    return ResolvedReference::ImplicitGlobal;
+                }
+            }
+
+            seen_function |= scope.kind.is_function();
             import_starred = import_starred || scope.uses_star_imports();
         }