JS: prove that KT-8315 is no more reproducible

js/js.tests/test/org/jetbrains/kotlin/js/test/semantics/BoxJsTestGenerated.java

@@ -6644,6 +6644,12 @@ public class BoxJsTestGenerated extends AbstractBoxJsTest {
             doTest(fileName);
         }
 
+        @TestMetadata("incDecOptimization.kt")
+        public void testIncDecOptimization() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("js/js.translator/testData/box/number/incDecOptimization.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("intConversions.kt")
         public void testIntConversions() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("js/js.translator/testData/box/number/intConversions.kt");

js/js.translator/testData/box/number/incDecOptimization.kt

+// EXPECTED_REACHABLE_NODES: 1029
+// CHECK_VARS_COUNT: function=test count=1
+
+class A {
+    var i = 23
+}
+
+fun test(a: A): String {
+    var x = ++a.i
+    if (x != 24) return "fail1: $x"
+
+    a.i++
+    if (a.i != 25) return "fail2: $a.i"
+
+    // a.i++, used as expression, requires temporary variable
+
+    return "OK"
+}
+
+fun box(): String = test(A())
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