If to when conversion preserves comments too

idea/src/org/jetbrains/kotlin/idea/intentions/branchedTransformations/intentions/IfToWhenIntention.kt

@@ -21,6 +21,7 @@ import com.intellij.openapi.util.TextRange
 import org.jetbrains.kotlin.idea.intentions.SelfTargetingRangeIntention
 import org.jetbrains.kotlin.idea.intentions.branchedTransformations.getSubjectToIntroduce
 import org.jetbrains.kotlin.idea.intentions.branchedTransformations.introduceSubject
+import org.jetbrains.kotlin.idea.util.CommentSaver
 import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.psi.*
 import java.util.*
@@ -32,6 +33,8 @@ class IfToWhenIntention : SelfTargetingRangeIntention<KtIfExpression>(KtIfExpres
     }
 
     override fun applyTo(element: KtIfExpression, editor: Editor?) {
+        val commentSaver = CommentSaver(element)
+
         var whenExpression = KtPsiFactory(element).buildExpression {
             appendFixedText("when {\n")
 
@@ -71,7 +74,8 @@ class IfToWhenIntention : SelfTargetingRangeIntention<KtIfExpression>(KtIfExpres
             whenExpression = whenExpression.introduceSubject()
         }
 
-        element.replace(whenExpression)
+        val result = element.replace(whenExpression)
+        commentSaver.restore(result)
     }
 
     private fun MutableList<KtExpression>.addOrBranches(expression: KtExpression): List<KtExpression> {

idea/testData/intentions/branched/ifWhen/ifToWhen/comment.kt

@@ -0,0 +1,4 @@
+fun foo(b: Boolean) {
+    <caret>if (b) 1 // 1
+    else 2
+}

idea/testData/intentions/branched/ifWhen/ifToWhen/comment.kt.after

@@ -0,0 +1,6 @@
+fun foo(b: Boolean) {
+    when {
+        b -> 1 // 1
+        else -> 2
+    }
+}

idea/tests/org/jetbrains/kotlin/idea/intentions/IntentionTestGenerated.java

@@ -1495,6 +1495,12 @@ public class IntentionTestGenerated extends AbstractIntentionTest {
                     KotlinTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("idea/testData/intentions/branched/ifWhen/ifToWhen"), Pattern.compile("^([\\w\\-_]+)\\.kt$"), true);
                 }
 
+                @TestMetadata("comment.kt")
+                public void testComment() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("idea/testData/intentions/branched/ifWhen/ifToWhen/comment.kt");
+                    doTest(fileName);
+                }
+
                 @TestMetadata("ifWithEqualityTests.kt")
                 public void testIfWithEqualityTests() throws Exception {
                     String fileName = KotlinTestUtils.navigationMetadata("idea/testData/intentions/branched/ifWhen/ifToWhen/ifWithEqualityTests.kt");