fix(es/minifier): Track if a var is used with in (#9508)

**Related issue:**

 - Closes #9499

.changeset/sour-pumpkins-rescue.md

@@ -0,0 +1,6 @@
+---
+swc_ecma_usage_analyzer: patch
+swc_core: patch
+---
+
+fix(es/minifier): Track if a var is used with `in`

crates/swc_ecma_minifier/tests/exec.rs

@@ -11347,6 +11347,19 @@ fn issue_9184_2() {
     );
 }
 
+#[test]
+fn issue_9499() {
+    run_default_exec_test(
+        "
+        const o = {'a': 1, 'b': 2};
+        function fn() {
+            return 'a' in o;
+        }
+        console.log(fn());
+",
+    )
+}
+
 #[test]
 fn issue_9356() {
     run_default_exec_test("console.log((function ({ } = 42) { }).length)");

crates/swc_ecma_usage_analyzer/src/analyzer/mod.rs

@@ -340,6 +340,7 @@ where
             if e.op == op!("in") {
                 for_each_id_ref_in_expr(&e.right, &mut |obj| {
                     let var = self.data.var_or_default(obj.to_id());
+                    var.mark_used_as_ref();
 
                     match &*e.left {
                         Expr::Lit(Lit::Str(prop)) if prop.value.parse::<f64>().is_err() => {