From f7dfd48eef453c0b2127b93ab3a55579445622c0 Mon Sep 17 00:00:00 2001
From: Bas Leijdekkers <bas.leijdekkers@jetbrains.com>
Date: Tue, 17 Mar 2026 17:53:42 +0100
Subject: [PATCH] IDEA-204102 [java]: use diamonds in initializer when
 replacing 'var' with explicit type

GitOrigin-RevId: fb9b55071bcfbc19fea0f56c3ec15dda52fd48ee
---
 .../quickfix/ReplaceVarWithExplicitTypeFix.java   | 15 ++++++++++-----
 .../quickFix/var2explicit/afterDiamonds.java      |  9 +++++++++
 .../quickFix/var2explicit/beforeDiamonds.java     |  9 +++++++++
 3 files changed, 28 insertions(+), 5 deletions(-)
 create mode 100644 java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/var2explicit/afterDiamonds.java
 create mode 100644 java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/var2explicit/beforeDiamonds.java

diff --git a/java/java-analysis-impl/src/com/intellij/codeInsight/daemon/impl/quickfix/ReplaceVarWithExplicitTypeFix.java b/java/java-analysis-impl/src/com/intellij/codeInsight/daemon/impl/quickfix/ReplaceVarWithExplicitTypeFix.java
index 94454f92bdcf..d1b8a9ac4b57 100644
--- a/java/java-analysis-impl/src/com/intellij/codeInsight/daemon/impl/quickfix/ReplaceVarWithExplicitTypeFix.java
+++ b/java/java-analysis-impl/src/com/intellij/codeInsight/daemon/impl/quickfix/ReplaceVarWithExplicitTypeFix.java
@@ -1,6 +1,7 @@
-// Copyright 2000-2024 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
+// Copyright 2000-2026 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.codeInspection.RemoveRedundantTypeArgumentsUtil;
 import com.intellij.codeInspection.VariableTypeCanBeExplicitInspection;
 import com.intellij.java.analysis.JavaAnalysisBundle;
 import com.intellij.modcommand.ActionContext;
@@ -9,6 +10,7 @@ import com.intellij.modcommand.Presentation;
 import com.intellij.modcommand.PsiUpdateModCommandAction;
 import com.intellij.psi.PsiElement;
 import com.intellij.psi.PsiLambdaExpression;
+import com.intellij.psi.PsiLocalVariable;
 import com.intellij.psi.PsiParameter;
 import com.intellij.psi.PsiTypeElement;
 import com.intellij.psi.PsiVariable;
@@ -30,17 +32,20 @@ public class ReplaceVarWithExplicitTypeFix extends PsiUpdateModCommandAction<Psi
 
   @Override
   protected void invoke(@NotNull ActionContext context, @NotNull PsiTypeElement startElement, @NotNull ModPsiUpdater updater) {
-    if (startElement.getParent() instanceof PsiParameter psiParameter &&
-        psiParameter.getDeclarationScope() instanceof PsiLambdaExpression lambda) {
+    if (startElement.getParent() instanceof PsiParameter p && p.getDeclarationScope() instanceof PsiLambdaExpression lambda) {
       for (PsiParameter parameter : lambda.getParameterList().getParameters()) {
         PsiTypeElement typeElement = parameter.getTypeElement();
         if (typeElement != null) {
           PsiTypesUtil.replaceWithExplicitType(typeElement);
         }
       }
-      return;
     }
-    PsiTypesUtil.replaceWithExplicitType(startElement);
+    else {
+      PsiTypeElement result = PsiTypesUtil.replaceWithExplicitType(startElement);
+      if (result != null && result.getParent() instanceof PsiLocalVariable var) {
+        RemoveRedundantTypeArgumentsUtil.removeRedundantTypeArguments(var.getInitializer());
+      }
+    }
   }
 
   @Override
diff --git a/java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/var2explicit/afterDiamonds.java b/java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/var2explicit/afterDiamonds.java
new file mode 100644
index 000000000000..d533fbf42ea5
--- /dev/null
+++ b/java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/var2explicit/afterDiamonds.java
@@ -0,0 +1,9 @@
+// "Replace 'var' with explicit type" "true-preview"
+import java.util.*;
+
+class X {
+  
+  void x() {
+      ArrayList<String> x = new ArrayList<>();
+  }
+}
\ No newline at end of file
diff --git a/java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/var2explicit/beforeDiamonds.java b/java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/var2explicit/beforeDiamonds.java
new file mode 100644
index 000000000000..4594bacb5b2d
--- /dev/null
+++ b/java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/var2explicit/beforeDiamonds.java
@@ -0,0 +1,9 @@
+// "Replace 'var' with explicit type" "true-preview"
+import java.util.*;
+
+class X {
+  
+  void x() {
+    var<caret> x = new ArrayList<String>();
+  }
+}
\ No newline at end of file