KT-13160: when decomposing assignment with lhs like array[index], extract array instead of supporting only qualifier.name`

js/js.inliner/src/org/jetbrains/kotlin/js/inline/ExpressionDecomposer.kt

@@ -183,10 +183,18 @@ internal class ExpressionDecomposer private constructor(
         }
 
         if (operator.isAssignment) {
-            // Must be (someThingWithSideEffect).x = arg2, because arg1 can have side effect
-            assert(arg1 is JsNameRef) { "Valid JavaScript left-hand side must be JsNameRef, got: $this" }
-            val arg1AsRef = arg1 as JsNameRef
-            arg1AsRef.qualifier = arg1AsRef.qualifier?.extractToTemporary()
+            val lhs = arg1
+            when (lhs) {
+                is JsNameRef -> {
+                    lhs.qualifier = lhs.qualifier?.extractToTemporary()
+                }
+                is JsArrayAccess -> {
+                    lhs.array = lhs.array.extractToTemporary()
+                }
+                else -> {
+                    error("Valid JavaScript left-hand side must be either JsNameRef or JsArrayAccess, got: $this")
+                }
+            }
         }
         else {
             arg1 = arg1.extractToTemporary()

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

@@ -77,6 +77,12 @@ public class InlineEvaluationOrderTestGenerated extends AbstractInlineEvaluation
         doTest(fileName);
     }
 
+    @TestMetadata("arrayAccessLhsDecomposed.kt")
+    public void testArrayAccessLhsDecomposed() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("js/js.translator/testData/inlineEvaluationOrder/cases/arrayAccessLhsDecomposed.kt");
+        doTest(fileName);
+    }
+
     @TestMetadata("arrayLiteral.kt")
     public void testArrayLiteral() throws Exception {
         String fileName = KotlinTestUtils.navigationMetadata("js/js.translator/testData/inlineEvaluationOrder/cases/arrayLiteral.kt");

js/js.translator/testData/inlineEvaluationOrder/cases/arrayAccessLhsDecomposed.kt

@@ -0,0 +1,16 @@
+package foo
+
+var global = ""
+
+class A(val data: Array<Int>)
+
+fun box(): String {
+    val a = A(arrayOf(1, 2, 3))
+    a.data[0] = listOf(1, 2, 3).fold(0) { a, b ->
+        global += "$b;"
+        a + b
+    }
+    assertEquals(6, a.data[0])
+    assertEquals("1;2;3;", global)
+    return "OK"
+}