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

#KT-5177 In Progress

compiler/testData/codegen/box/controlStructures/forInIterableWithIndex/forInEmptyListWithIndex.kt

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

compiler/testData/codegen/box/controlStructures/forInIterableWithIndex/forInListWithIndex.kt

@@ -0,0 +1,14 @@
+// WITH_RUNTIME
+
+val xs = listOf("a", "b", "c", "d")
+
+fun box(): String {
+    val s = StringBuilder()
+
+    for ((index, x) in xs.withIndex()) {
+        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/forInIterableWithIndex/forInListWithIndexNoElementVar.kt

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

compiler/testData/codegen/box/controlStructures/forInIterableWithIndex/forInListWithIndexNoIndexVar.kt

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

compiler/testData/codegen/box/controlStructures/forInIterableWithIndex/forInListWithIndexThrowsCME.kt

@@ -0,0 +1,24 @@
+// IGNORE_BACKEND: JS, NATIVE
+// FULL_JDK
+// WITH_RUNTIME
+
+val xs = arrayListOf("a", "b", "c", "d")
+
+fun box(): String {
+    val s = StringBuilder()
+
+    var cmeThrown = false
+    try {
+        for ((index, x) in xs.withIndex()) {
+            s.append("$index:$x;")
+            xs.clear()
+        }
+    } catch (e: java.util.ConcurrentModificationException) {
+        cmeThrown = true
+    }
+
+    if (!cmeThrown) return "Fail: CME should be thrown"
+
+    val ss = s.toString()
+    return if (ss == "0:a;") "OK" else "fail: '$ss'"
+}

compiler/testData/codegen/box/controlStructures/forInIterableWithIndex/forInListWithIndexWithExplicitlyTypedIndexVariable.kt

@@ -0,0 +1,17 @@
+// WITH_RUNTIME
+
+val xs = listOf("a", "b", "c", "d")
+
+fun useAny(x: Any) {}
+
+fun box(): String {
+    val s = StringBuilder()
+
+    for ((index: Any, x) in xs.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'"
+}