Add tracking bug comment.

src/Workspaces/Core/Portable/EmbeddedLanguages/RegularExpressions/RegexParser.cs

@@ -1250,8 +1250,8 @@ private void ParseCharacterClassComponents(ArrayBuilder<RegexExpressionNode> com
                 {
                     var right = ParseRightSideOfCharacterClassRange();
 
-                    if (TryGetRangeComponentValue(left, isRight: false, out var leftCh) &&
-                        TryGetRangeComponentValue(right, isRight: true, out var rightCh) &&
+                    if (TryGetRangeComponentValue(left, out var leftCh) &&
+                        TryGetRangeComponentValue(right, out var rightCh) &&
                         leftCh > rightCh)
                     {
                         minusToken = minusToken.AddDiagnosticIfNone(new EmbeddedDiagnostic(
@@ -1271,7 +1271,7 @@ private void ParseCharacterClassComponents(ArrayBuilder<RegexExpressionNode> com
         private bool IsEscapedMinus(RegexNode node)
             => node is RegexSimpleEscapeNode simple && IsTextChar(simple.TypeToken, '-');
 
-        private bool TryGetRangeComponentValue(RegexExpressionNode component, bool isRight, out char ch)
+        private bool TryGetRangeComponentValue(RegexExpressionNode component, out char ch)
         {
             // Don't bother examining the component if it has any errors already.  This also means
             // we don't have to worry about running into invalid escape sequences and the like.
@@ -1437,6 +1437,8 @@ private RegexExpressionNode ParseRightSideOfCharacterClassRange()
             // is legal [a-\-] (even though \- is less than 'a'). Similarly, the following are
             // *illegal* [b-\-a] and [b-\-\-a].  That's because the range that is checked is
             // actually "b-a", even though it has all the \- escapes in the middle.
+            //
+            // This is tracked with: https://github.com/dotnet/corefx/issues/31786
 
             var first = ParseSingleCharacterClassComponent(isFirst: false, afterRangeMinus: true);
             if (!IsEscapedMinus(first))