Supported other patterns for mapNotNull

idea/src/org/jetbrains/kotlin/idea/intentions/loopToCallChain/sequence/FilterTransformation.kt

@@ -163,6 +163,13 @@ class FilterIsInstanceTransformation(
 }
 
 class FilterNotNullTransformation(override val loop: KtForExpression) : SequenceTransformation {
+    override fun mergeWithPrevious(previousTransformation: SequenceTransformation): SequenceTransformation? {
+        return when (previousTransformation) {
+            is MapTransformation -> MapNotNullTransformation(loop, previousTransformation.inputVariable, previousTransformation.mapping)
+            is MapIndexedTransformation -> MapIndexedNotNullTransformation(loop, previousTransformation.inputVariable, previousTransformation.indexVariable, previousTransformation.mapping)
+            else -> null
+        }
+    }
 
     override val affectsIndex: Boolean
         get() = true

idea/testData/intentions/loopToCallChain/mapIndexedNotNull.kt

@@ -0,0 +1,9 @@
+// WITH_RUNTIME
+// INTENTION_TEXT: "Replace with 'mapIndexedNotNull{}.mapTo(){}'"
+fun foo(list: List<String?>, target: MutableList<String>) {
+    <caret>for ((index, s) in list.withIndex()) {
+        val length = s?.substring(index)?.length
+        if (length == null) continue
+        target.add(length.toString())
+    }
+}

idea/testData/intentions/loopToCallChain/mapIndexedNotNull.kt.after

@@ -0,0 +1,7 @@
+// WITH_RUNTIME
+// INTENTION_TEXT: "Replace with 'mapIndexedNotNull{}.mapTo(){}'"
+fun foo(list: List<String?>, target: MutableList<String>) {
+    <caret>list
+            .mapIndexedNotNull { index, s -> s?.substring(index)?.length }
+            .mapTo(target) { it.toString() }
+}

idea/testData/intentions/loopToCallChain/mapNotNull.kt

@@ -0,0 +1,9 @@
+// WITH_RUNTIME
+// INTENTION_TEXT: "Replace with 'mapNotNull{}.mapTo(){}'"
+fun foo(list: List<String?>, target: MutableList<String>) {
+    <caret>for (s in list) {
+        val length = s?.length
+        if (length == null) continue
+        target.add(length.toString())
+    }
+}

idea/testData/intentions/loopToCallChain/mapNotNull.kt.after

@@ -0,0 +1,7 @@
+// WITH_RUNTIME
+// INTENTION_TEXT: "Replace with 'mapNotNull{}.mapTo(){}'"
+fun foo(list: List<String?>, target: MutableList<String>) {
+    <caret>list
+            .mapNotNull { it?.length }
+            .mapTo(target) { it.toString() }
+}