[java] Preserve comments in ReturnReplacementContext#stripUnnecessaryBlocks

#IDEA-369976 Fixed

GitOrigin-RevId: d20a4a7d92ffb5fc7bda36c879868a2d3e2e8413

java/java-impl/src/com/intellij/codeInsight/intention/impl/singlereturn/ReturnReplacementContext.java

@@ -1,4 +1,4 @@
-// Copyright 2000-2024 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
+// Copyright 2000-2025 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
 package com.intellij.codeInsight.intention.impl.singlereturn;
 
 import com.intellij.codeInsight.BlockUtils;
@@ -21,7 +21,7 @@ import static com.intellij.util.ObjectUtils.tryCast;
 import static java.util.Objects.requireNonNull;
 
 /**
- * Performs replacement of single return statement as the part of {@link ConvertToSingleReturnAction}.
+ * Performs replacement of a single return statement as the part of {@link ConvertToSingleReturnAction}.
  */
 final class ReturnReplacementContext {
   private final Project myProject;
@@ -296,7 +296,7 @@ final class ReturnReplacementContext {
         if (parentIf != null && parentIf.getElseBranch() == place) {
           PsiIfStatement childIf = tryCast(ControlFlowUtils.stripBraces((PsiStatement)place), PsiIfStatement.class);
           if (childIf != null) {
-            place = place.replace(childIf);
+            place = new CommentTracker().replaceAndRestoreComments(place, childIf);
           }
         }
       }

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/convertToSingleReturn/afterPreserveComments.java

@@ -0,0 +1,20 @@
+// "Transform body to single exit-point form" "true-preview"
+class Test {
+    int foo(int i) {
+        int result = -1;
+        // comment 1
+        // comment 5
+        // comment 6
+        if (i == 0) { // comment 2
+          // comment 3
+            result = 1;// comment 4
+        } else if (i == 1) { // comment 7
+          // comment 8
+            result = 0;// comment 9
+        } // comment 10
+        // comment 11
+
+
+        return result;
+    }
+}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/convertToSingleReturn/beforePreserveComments.java

@@ -0,0 +1,20 @@
+// "Transform body to single exit-point form" "true-preview"
+class Test {
+    int fo<caret>o(int i) {
+        // comment 1
+        if (i == 0) { // comment 2
+          // comment 3
+          return 1; // comment 4
+        }
+        // comment 5
+
+        // comment 6
+        if (i == 1) { // comment 7
+          // comment 8
+          return 0; // comment 9
+        }
+
+        // comment 10
+        return -1; // comment 11
+    }
+}