Java: keep final if possible when reusing previous variable (IDEA-312181)

GitOrigin-RevId: 73e54a9e8850f2fa04ac2b642e712c285f5b24f6

java/java-impl/src/com/intellij/codeInsight/daemon/impl/quickfix/ReuseVariableDeclarationFix.java

@@ -1,21 +1,8 @@
-/*
- * Copyright 2000-2016 JetBrains s.r.o.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
+// Copyright 2000-2023 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
 package com.intellij.codeInsight.daemon.impl.quickfix;
 
 import com.intellij.codeInsight.daemon.QuickFixBundle;
+import com.intellij.codeInsight.daemon.impl.analysis.HighlightControlFlowUtil;
 import com.intellij.codeInsight.intention.FileModifier;
 import com.intellij.codeInsight.intention.IntentionAction;
 import com.intellij.codeInsight.intention.impl.BaseIntentionAction;
@@ -79,12 +66,18 @@ public class ReuseVariableDeclarationFix implements IntentionAction {
       return;
     }
 
+    boolean wasFinal = refVariable.hasModifierProperty(PsiModifier.FINAL);
     PsiUtil.setModifierProperty(refVariable, PsiModifier.FINAL, false);
     final PsiElementFactory factory = JavaPsiFacade.getElementFactory(myVariable.getProject());
     final PsiElement statement = factory.createStatementFromText(
       myVariable.getName() + " = " +
       ExpressionUtils.convertInitializerToExpression(initializer, factory, myVariable.getType()).getText() + ";", null);
     myVariable.getParent().replace(statement);
+    if (wasFinal &&
+        refVariable instanceof PsiLocalVariable &&
+        HighlightControlFlowUtil.isEffectivelyFinal(refVariable, initializer, null)) {
+      PsiUtil.setModifierProperty(refVariable, PsiModifier.FINAL, true);
+    }
   }
 
   @Nullable

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/reuseVariableDeclaration/afterFinal.java

@@ -0,0 +1,14 @@
+// "Reuse previous variable 'x' declaration" "true-preview"
+import java.io.*;
+
+class X {
+  public void demo() {
+    final boolean x;
+    if (true) {
+      x = false;
+    } else {
+        x = true;
+    }
+  }
+}
+

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/reuseVariableDeclaration/beforeFinal.java

@@ -0,0 +1,14 @@
+// "Reuse previous variable 'x' declaration" "true-preview"
+import java.io.*;
+
+class X {
+  public void demo() {
+    final boolean x;
+    if (true) {
+      x = false;
+    } else {
+      boolean <caret>x = true;
+    }
+  }
+}
+