Make unpacked assignment a flag rather than a BindingKind (#8595)

## Summary

An assignment can be _both_ (e.g.) a loop variable _and_ assigned via
unpacking. In other words, unpacking is a quality of an assignment, not
a _kind_.

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

@@ -1615,38 +1615,23 @@ impl<'a> Checker<'a> {
     fn handle_node_store(&mut self, id: &'a str, expr: &Expr) {
         let parent = self.semantic.current_statement();
 
+        let mut flags = BindingFlags::empty();
+        if helpers::is_unpacking_assignment(parent, expr) {
+            flags.insert(BindingFlags::UNPACKED_ASSIGNMENT);
+        }
+
         // Match the left-hand side of an annotated assignment, like `x` in `x: int`.
         if matches!(
             parent,
             Stmt::AnnAssign(ast::StmtAnnAssign { value: None, .. })
         ) && !self.semantic.in_annotation()
         {
-            self.add_binding(
-                id,
-                expr.range(),
-                BindingKind::Annotation,
-                BindingFlags::empty(),
-            );
+            self.add_binding(id, expr.range(), BindingKind::Annotation, flags);
             return;
         }
 
         if parent.is_for_stmt() {
-            self.add_binding(
-                id,
-                expr.range(),
-                BindingKind::LoopVar,
-                BindingFlags::empty(),
-            );
-            return;
-        }
-
-        if helpers::is_unpacking_assignment(parent, expr) {
-            self.add_binding(
-                id,
-                expr.range(),
-                BindingKind::UnpackedAssignment,
-                BindingFlags::empty(),
-            );
+            self.add_binding(id, expr.range(), BindingKind::LoopVar, flags);
             return;
         }
 
@@ -1681,7 +1666,6 @@ impl<'a> Checker<'a> {
             let (all_names, all_flags) =
                 extract_all_names(parent, |name| self.semantic.is_builtin(name));
 
-            let mut flags = BindingFlags::empty();
             if all_flags.intersects(DunderAllFlags::INVALID_OBJECT) {
                 flags |= BindingFlags::INVALID_ALL_OBJECT;
             }
@@ -1705,21 +1689,11 @@ impl<'a> Checker<'a> {
             .current_expressions()
             .any(Expr::is_named_expr_expr)
         {
-            self.add_binding(
-                id,
-                expr.range(),
-                BindingKind::NamedExprAssignment,
-                BindingFlags::empty(),
-            );
+            self.add_binding(id, expr.range(), BindingKind::NamedExprAssignment, flags);
             return;
         }
 
-        self.add_binding(
-            id,
-            expr.range(),
-            BindingKind::Assignment,
-            BindingFlags::empty(),
-        );
+        self.add_binding(id, expr.range(), BindingKind::Assignment, flags);
     }
 
     fn handle_node_delete(&mut self, expr: &'a Expr) {

crates/ruff_linter/src/renamer.rs

@@ -245,7 +245,6 @@ impl Renamer {
             | BindingKind::Argument
             | BindingKind::TypeParam
             | BindingKind::NamedExprAssignment
-            | BindingKind::UnpackedAssignment
             | BindingKind::Assignment
             | BindingKind::BoundException
             | BindingKind::LoopVar

crates/ruff_linter/src/rules/pandas_vet/helpers.rs

@@ -46,7 +46,6 @@ pub(super) fn test_expression(expr: &Expr, semantic: &SemanticModel) -> Resoluti
                         BindingKind::Annotation
                         | BindingKind::Assignment
                         | BindingKind::NamedExprAssignment
-                        | BindingKind::UnpackedAssignment
                         | BindingKind::LoopVar
                         | BindingKind::Global
                         | BindingKind::Nonlocal(_) => Resolution::RelevantLocal,

crates/ruff_linter/src/rules/pyflakes/rules/unused_variable.rs

@@ -322,10 +322,9 @@ pub(crate) fn unused_variable(checker: &Checker, scope: &Scope, diagnostics: &mu
         .bindings()
         .map(|(name, binding_id)| (name, checker.semantic().binding(binding_id)))
         .filter_map(|(name, binding)| {
-            if (binding.kind.is_assignment()
-                || binding.kind.is_named_expr_assignment()
-                || (matches!(checker.settings.preview, PreviewMode::Enabled)
-                    && binding.kind.is_unpacked_assignment()))
+            if (binding.kind.is_assignment() || binding.kind.is_named_expr_assignment())
+                && (!binding.is_unpacked_assignment()
+                    || matches!(checker.settings.preview, PreviewMode::Enabled))
                 && !binding.is_nonlocal()
                 && !binding.is_global()
                 && !binding.is_used()

crates/ruff_linter/src/rules/pylint/rules/non_ascii_name.rs

@@ -49,7 +49,6 @@ pub(crate) fn non_ascii_name(binding: &Binding, locator: &Locator) -> Option<Dia
         BindingKind::Annotation => Kind::Annotation,
         BindingKind::Argument => Kind::Argument,
         BindingKind::NamedExprAssignment => Kind::NamedExprAssignment,
-        BindingKind::UnpackedAssignment => Kind::UnpackedAssignment,
         BindingKind::Assignment => Kind::Assignment,
         BindingKind::TypeParam => Kind::TypeParam,
         BindingKind::LoopVar => Kind::LoopVar,
@@ -85,7 +84,6 @@ enum Kind {
     Annotation,
     Argument,
     NamedExprAssignment,
-    UnpackedAssignment,
     Assignment,
     TypeParam,
     LoopVar,
@@ -102,7 +100,6 @@ impl fmt::Display for Kind {
             Kind::Annotation => f.write_str("Annotation"),
             Kind::Argument => f.write_str("Argument"),
             Kind::NamedExprAssignment => f.write_str("Variable"),
-            Kind::UnpackedAssignment => f.write_str("Variable"),
             Kind::Assignment => f.write_str("Variable"),
             Kind::TypeParam => f.write_str("Type parameter"),
             Kind::LoopVar => f.write_str("Variable"),

crates/ruff_python_semantic/src/binding.rs

@@ -87,6 +87,12 @@ impl<'a> Binding<'a> {
         self.flags.intersects(BindingFlags::INVALID_ALL_OBJECT)
     }
 
+    /// Return `true` if this [`Binding`] represents an unpacked assignment (e.g., `x` in
+    /// `(x, y) = 1, 2`).
+    pub const fn is_unpacked_assignment(&self) -> bool {
+        self.flags.intersects(BindingFlags::UNPACKED_ASSIGNMENT)
+    }
+
     /// Return `true` if this [`Binding`] represents an unbound variable
     /// (e.g., `x` in `x = 1; del x`).
     pub const fn is_unbound(&self) -> bool {
@@ -212,7 +218,7 @@ impl<'a> Binding<'a> {
 bitflags! {
     /// Flags on a [`Binding`].
     #[derive(Debug, Default, Copy, Clone, Eq, PartialEq)]
-    pub struct BindingFlags: u8 {
+    pub struct BindingFlags: u16 {
         /// The binding represents an explicit re-export.
         ///
         /// For example, the binding could be `FastAPI` in:
@@ -284,6 +290,14 @@ bitflags! {
         /// _T = "This is a private variable"
         /// ```
         const PRIVATE_DECLARATION = 1 << 7;
+
+        /// The binding represents an unpacked assignment.
+        ///
+        /// For example, the binding could be `x` in:
+        /// ```python
+        /// (x, y) = 1, 2
+        /// ```
+        const UNPACKED_ASSIGNMENT = 1 << 8;
     }
 }
 
@@ -393,12 +407,6 @@ pub enum BindingKind<'a> {
     /// ```
     NamedExprAssignment,
 
-    /// A binding for a unpacking-based assignment, like `x` in:
-    /// ```python
-    /// x, y = (1, 2)
-    /// ```
-    UnpackedAssignment,
-
     /// A binding for a "standard" assignment, like `x` in:
     /// ```python
     /// x = 1