[tests] add test for #9388

tests/optimization/src/issues/Issue9388.hx

@@ -0,0 +1,13 @@
+package issues;
+
+class Issue9388 {
+	var x(default,set):Int;
+	function set_x(v) return v;
+
+	@:js('
+		this.set_x(this.x + 1);
+	')
+	function f() {
+		x++;
+	}
+}