RegExp: Escape ] correctly if it was unnecessarily escaped before (IDEA-195762)

RegExpSupport/src/org/intellij/lang/regexp/inspection/SingleCharAlternationInspection.java

@@ -105,7 +105,13 @@ public class SingleCharAlternationInspection extends LocalInspectionTool {
         final RegExpChar ch = (RegExpChar)child;
         final IElementType type = ch.getNode().getFirstChildNode().getElementType();
         if (type == RegExpTT.REDUNDANT_ESCAPE) {
-          text.append((char)ch.getValue());
+          final int value = ch.getValue();
+          if (value == ']') {
+            text.append(ch.getUnescapedText());
+          }
+          else {
+            text.append((char)value);
+          }
         }
         else if (type == RegExpTT.ESC_CHARACTER) {
           final int value = ch.getValue();

RegExpSupport/test/org/intellij/lang/regexp/inspection/SingleCharAlternationInspectionTest.java

@@ -39,6 +39,10 @@ public class SingleCharAlternationInspectionTest extends RegExpInspectionTestCas
                  "([.\\[\\](){}^?*|+\\-$])ab", "Replace with '[.\\[\\](){}^?*|+\\-$]'");
   }
 
+  public void testRedundantEscapeReplacement() {
+    quickfixTest("(<warning descr=\"Single character alternation in RegExp\">\\[<caret>|\\]</warning>)", "([\\[\\]])", "Replace with '[\\[\\]]");
+  }
+
   @NotNull
   @Override
   protected LocalInspectionTool getInspection() {