"Replace if with when": do not add empty else block #KT-18681 Fixed

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

@@ -63,7 +63,7 @@ class IfToWhenIntention : SelfTargetingRangeIntention<KtIfExpression>(KtIfExpres
                     builder.append(nextSibling.text)
                     nextSibling = nextSibling.nextSibling ?: break
                 }
-                KtPsiFactory(ifExpression).createBlock(builder.toString())
+                KtPsiFactory(ifExpression).createBlock(builder.toString()).takeIf { it.statements.isNotEmpty() }
             }
         }
     }

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

@@ -0,0 +1,8 @@
+fun test(a: Any, b: Boolean): Int  {
+    when (a) {
+        is Int -> {
+            <caret>if (b) return 1
+        }
+    }
+    return 0
+}

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

@@ -0,0 +1,10 @@
+fun test(a: Any, b: Boolean): Int  {
+    when (a) {
+        is Int -> {
+            when {
+                b -> return 1
+            }
+        }
+    }
+    return 0
+}

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

@@ -2514,6 +2514,11 @@ public class IntentionTestGenerated extends AbstractIntentionTest {
                     runTest("idea/testData/intentions/branched/ifWhen/ifToWhen/ifElseSwallowTail.kt");
                 }
 
+                @TestMetadata("ifThenReturn.kt")
+                public void testIfThenReturn() throws Exception {
+                    runTest("idea/testData/intentions/branched/ifWhen/ifToWhen/ifThenReturn.kt");
+                }
+
                 @TestMetadata("ifWithEqualityTests.kt")
                 public void testIfWithEqualityTests() throws Exception {
                     runTest("idea/testData/intentions/branched/ifWhen/ifToWhen/ifWithEqualityTests.kt");