Replace return with 'if'/'when': don't drop return label

#KT-30414 Fixed

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

@@ -50,16 +50,23 @@ class UnfoldReturnToIfIntention : LowPriorityAction, SelfTargetingRangeIntention
         val psiFactory = KtPsiFactory(element)
         val context = element.analyze()
 
-        newThenExpr.replace(createReturnExpression(thenExpr, psiFactory, context))
+        val labelName = element.getLabelName()
-        newElseExpr.replace(createReturnExpression(elseExpr, psiFactory, context))
+        newThenExpr.replace(createReturnExpression(thenExpr, labelName, psiFactory, context))
+        newElseExpr.replace(createReturnExpression(elseExpr, labelName, psiFactory, context))
         element.replace(newIfExpression)
     }
 
     companion object {
-        fun createReturnExpression(expr: KtExpression, psiFactory: KtPsiFactory, context: BindingContext): KtExpression {
+        fun createReturnExpression(
+            expr: KtExpression,
+            labelName: String?,
+            psiFactory: KtPsiFactory,
+            context: BindingContext
+        ): KtExpression {
+            val label = labelName?.let { "@$it" } ?: ""
             val returnText = when (expr) {
                 is KtBreakExpression, is KtContinueExpression, is KtReturnExpression, is KtThrowExpression -> ""
-                else -> if (expr.getResolvedCall(context)?.resultingDescriptor?.returnType?.isNothing() == true) "" else "return "
+                else -> if (expr.getResolvedCall(context)?.resultingDescriptor?.returnType?.isNothing() == true) "" else "return$label "
             }
             return psiFactory.createExpressionByPattern("$returnText$0", expr)
         }

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

@@ -44,10 +44,11 @@ class UnfoldReturnToWhenIntention : LowPriorityAction, SelfTargetingRangeIntenti
         val whenExpression = element.returnedExpression as KtWhenExpression
         val newWhenExpression = whenExpression.copied()
 
+        val labelName = element.getLabelName()
         whenExpression.entries.zip(newWhenExpression.entries).forEach { (entry, newEntry) ->
             val expr = entry.expression!!.lastBlockStatementOrThis()
             val newExpr = newEntry.expression!!.lastBlockStatementOrThis()
-            newExpr.replace(UnfoldReturnToIfIntention.createReturnExpression(expr, psiFactory, context))
+            newExpr.replace(UnfoldReturnToIfIntention.createReturnExpression(expr, labelName, psiFactory, context))
         }
         element.replace(newWhenExpression)
     }

idea/testData/intentions/branched/unfolding/returnToIf/labeledReturn.kt

@@ -0,0 +1,10 @@
+// WITH_RUNTIME
+fun main() {
+    run label@{
+        <caret>return@label if (true) {
+            42
+        } else {
+            42
+        }
+    }
+}

idea/testData/intentions/branched/unfolding/returnToIf/labeledReturn.kt.after

@@ -0,0 +1,10 @@
+// WITH_RUNTIME
+fun main() {
+    run label@{
+        <caret>if (true) {
+            return@label 42
+        } else {
+            return@label 42
+        }
+    }
+}

idea/testData/intentions/branched/unfolding/returnToWhen/labeledReturn.kt

@@ -0,0 +1,10 @@
+// WITH_RUNTIME
+fun main() {
+    run label@{
+        <caret>return@label when {
+            true ->
+                42
+            else -> 42
+        }
+    }
+}

idea/testData/intentions/branched/unfolding/returnToWhen/labeledReturn.kt.after

@@ -0,0 +1,10 @@
+// WITH_RUNTIME
+fun main() {
+    run label@{
+        <caret>when {
+            true ->
+                return@label 42
+            else -> return@label 42
+        }
+    }
+}

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

@@ -3416,6 +3416,11 @@ public class IntentionTestGenerated extends AbstractIntentionTest {
                     runTest("idea/testData/intentions/branched/unfolding/returnToIf/innerIfTransformed.kt");
                 }
 
+                @TestMetadata("labeledReturn.kt")
+                public void testLabeledReturn() throws Exception {
+                    runTest("idea/testData/intentions/branched/unfolding/returnToIf/labeledReturn.kt");
+                }
+
                 @TestMetadata("simpleIf.kt")
                 public void testSimpleIf() throws Exception {
                     runTest("idea/testData/intentions/branched/unfolding/returnToIf/simpleIf.kt");
@@ -3444,6 +3449,11 @@ public class IntentionTestGenerated extends AbstractIntentionTest {
                     runTest("idea/testData/intentions/branched/unfolding/returnToWhen/innerWhenTransformed.kt");
                 }
 
+                @TestMetadata("labeledReturn.kt")
+                public void testLabeledReturn() throws Exception {
+                    runTest("idea/testData/intentions/branched/unfolding/returnToWhen/labeledReturn.kt");
+                }
+
                 @TestMetadata("simpleWhen.kt")
                 public void testSimpleWhen() throws Exception {
                     runTest("idea/testData/intentions/branched/unfolding/returnToWhen/simpleWhen.kt");