From 0498719d5422843967a4d31bd686f9717dcc290e Mon Sep 17 00:00:00 2001
From: Bas Leijdekkers <bas.leijdekkers@jetbrains.com>
Date: Tue, 24 Jun 2025 15:42:39 +0200
Subject: [PATCH] RegExp: warn about duplicate char in character class with
 intersection (IJPL-193556)

for "Duplicate character in character class" inspection

GitOrigin-RevId: 455aff90e2c52c735df582fced65225b5ecbb2f0
---
 .../inspection/DuplicateCharacterInClassInspection.java   | 8 +++++++-
 .../DuplicateCharacterInClassInspectionTest.java          | 7 ++++++-
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/RegExpSupport/src/org/intellij/lang/regexp/inspection/DuplicateCharacterInClassInspection.java b/RegExpSupport/src/org/intellij/lang/regexp/inspection/DuplicateCharacterInClassInspection.java
index fed9dad0ad45..c34387d2697d 100644
--- a/RegExpSupport/src/org/intellij/lang/regexp/inspection/DuplicateCharacterInClassInspection.java
+++ b/RegExpSupport/src/org/intellij/lang/regexp/inspection/DuplicateCharacterInClassInspection.java
@@ -1,4 +1,4 @@
-// Copyright 2000-2020 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+// Copyright 2000-2025 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
 package org.intellij.lang.regexp.inspection;
 
 import com.intellij.codeInspection.LocalInspectionTool;
@@ -63,6 +63,12 @@ public class DuplicateCharacterInClassInspection extends LocalInspectionTool {
                                    new DuplicateCharacterInClassFix(regExpSimpleClass));
         }
       }
+      else if (element instanceof RegExpIntersection intersection) {
+        final HashSet<Object> visited = new HashSet<>();
+        for (RegExpClassElement operand : intersection.getOperands()) {
+          checkForDuplicates(operand, visited);
+        }
+      }
     }
   }
 
diff --git a/RegExpSupport/test/org/intellij/lang/regexp/inspection/DuplicateCharacterInClassInspectionTest.java b/RegExpSupport/test/org/intellij/lang/regexp/inspection/DuplicateCharacterInClassInspectionTest.java
index 0e4042b96e2a..c0be4607e6f4 100644
--- a/RegExpSupport/test/org/intellij/lang/regexp/inspection/DuplicateCharacterInClassInspectionTest.java
+++ b/RegExpSupport/test/org/intellij/lang/regexp/inspection/DuplicateCharacterInClassInspectionTest.java
@@ -1,4 +1,4 @@
-// Copyright 2000-2020 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+// Copyright 2000-2025 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
 package org.intellij.lang.regexp.inspection;
 
 import com.intellij.codeInspection.LocalInspectionTool;
@@ -8,6 +8,7 @@ import org.jetbrains.annotations.NotNull;
 /**
  * @author Bas Leijdekkers
  */
+@SuppressWarnings("RegExpDuplicateCharacterInClass")
 public class DuplicateCharacterInClassInspectionTest extends RegExpInspectionTestCase {
 
   public void testPredefinedCharacterClass() {
@@ -34,6 +35,10 @@ public class DuplicateCharacterInClassInspectionTest extends RegExpInspectionTes
   public void testNestedClass() {
     highlightTest("[<[^<>]*>]*<[^<>]*");
   }
+  
+  public void testIntersection() {
+    highlightTest("[\\w<warning descr=\"Duplicate predefined character class '\\w' inside character class\">\\w</warning>&&[^_]]");
+  }
 
   @Override
   protected @NotNull LocalInspectionTool getInspection() {