From 1f888e277b6fdb2e755828d7ea3167a0f1bf26bd Mon Sep 17 00:00:00 2001
From: David Peter <mail@david-peter.de>
Date: Mon, 18 Nov 2024 13:38:40 +0100
Subject: [PATCH] Try to fix perf regression

---
 crates/red_knot_python_semantic/src/types/narrow.rs | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/crates/red_knot_python_semantic/src/types/narrow.rs b/crates/red_knot_python_semantic/src/types/narrow.rs
index e62f566d260acd..fb56a9e2c0b55e 100644
--- a/crates/red_knot_python_semantic/src/types/narrow.rs
+++ b/crates/red_knot_python_semantic/src/types/narrow.rs
@@ -278,8 +278,6 @@ impl<'db> NarrowingConstraintsBuilder<'db> {
             .tuple_windows::<(&ruff_python_ast::Expr, &ruff_python_ast::Expr)>();
         let mut constraints = NarrowingConstraints::default();
         for (op, (left, right)) in std::iter::zip(&**ops, comparator_tuples) {
-            let rhs_ty = inference.expression_ty(right.scoped_expression_id(self.db, scope));
-
             match left {
                 ast::Expr::Name(ast::ExprName {
                     range: _,
@@ -288,6 +286,8 @@ impl<'db> NarrowingConstraintsBuilder<'db> {
                 }) => {
                     // SAFETY: we should always have a symbol for every Name node.
                     let symbol = self.symbols().symbol_id_by_name(id).unwrap();
+                    let rhs_ty =
+                        inference.expression_ty(right.scoped_expression_id(self.db, scope));
 
                     match if is_positive { *op } else { op.negate() } {
                         ast::CmpOp::IsNot => {
@@ -333,6 +333,8 @@ impl<'db> NarrowingConstraintsBuilder<'db> {
                         if let Some(id) = arguments.args[0].as_name_expr().map(|name| &name.id) {
                             let symbol = self.symbols().symbol_id_by_name(id).unwrap();
                             if ast::CmpOp::Is == if is_positive { *op } else { op.negate() } {
+                                let rhs_ty = inference
+                                    .expression_ty(right.scoped_expression_id(self.db, scope));
                                 if rhs_ty.is_class_literal() {
                                     constraints.insert(symbol, rhs_ty.to_instance(self.db));
                                 }