Provide optimized code generation for for-in-withIndex for arrays

#KT-5177 In Progress

compiler/testData/codegen/box/controlStructures/forInArrayWithIndex/forInArrrayWithIndexNoElementVar.kt

@@ -0,0 +1,14 @@
+// WITH_RUNTIME
+
+val arr = arrayOf("a", "b", "c", "d")
+
+fun box(): String {
+    val s = StringBuilder()
+
+    for ((i, _) in arr.withIndex()) {
+        s.append("$i;")
+    }
+
+    val ss = s.toString()
+    return if (ss == "0;1;2;3;") "OK" else "fail: '$ss'"
+}

compiler/testData/codegen/box/controlStructures/forInArrayWithIndex/forInArrrayWithIndexNoIndexVar.kt

@@ -0,0 +1,14 @@
+// WITH_RUNTIME
+
+val arr = arrayOf("a", "b", "c", "d")
+
+fun box(): String {
+    val s = StringBuilder()
+
+    for ((_, x) in arr.withIndex()) {
+        s.append("$x;")
+    }
+
+    val ss = s.toString()
+    return if (ss == "a;b;c;d;") "OK" else "fail: '$ss'"
+}

compiler/testData/codegen/box/controlStructures/forInArrayWithIndex/forInArrrayWithIndexWithExplicitlyTypedIndexVariable.kt

@@ -0,0 +1,17 @@
+// WITH_RUNTIME
+
+val arr = arrayOf("a", "b", "c", "d")
+
+fun useAny(x: Any) {}
+
+fun box(): String {
+    val s = StringBuilder()
+
+    for ((index: Any, x) in arr.withIndex()) {
+        useAny(index)
+        s.append("$index:$x;")
+    }
+
+    val ss = s.toString()
+    return if (ss == "0:a;1:b;2:c;3:d;") "OK" else "fail: '$ss'"
+}

compiler/testData/codegen/box/controlStructures/forInArrayWithIndex/forInEmptyArrrayWithIndex.kt

@@ -0,0 +1,11 @@
+// WITH_RUNTIME
+
+val arr = intArrayOf()
+
+fun box(): String {
+    val s = StringBuilder()
+    for ((index, x) in arr.withIndex()) {
+        return "Loop over empty array should not be executed"
+    }
+    return "OK"
+}

compiler/testData/codegen/box/controlStructures/forInArrayWithIndex/forInIntArrrayWithIndex.kt

@@ -0,0 +1,12 @@
+// WITH_RUNTIME
+
+val arr = intArrayOf(10, 20, 30, 40)
+
+fun box(): String {
+    val s = StringBuilder()
+    for ((index, x) in arr.withIndex()) {
+        s.append("$index:$x;")
+    }
+    val ss = s.toString()
+    return if (ss == "0:10;1:20;2:30;3:40;") "OK" else "fail: '$ss'"
+}

compiler/testData/codegen/box/controlStructures/forInArrayWithIndex/forInObjectArrrayWithIndex.kt

@@ -0,0 +1,14 @@
+// WITH_RUNTIME
+
+val arr = arrayOf("a", "b", "c", "d")
+
+fun box(): String {
+    val s = StringBuilder()
+
+    for ((index, x) in arr.withIndex()) {
+        s.append("$index:$x;")
+    }
+
+    val ss = s.toString()
+    return if (ss == "0:a;1:b;2:c;3:d;") "OK" else "fail: '$ss'"
+}