C#: Handle op_Checked* operators in the extractor

Author: hvitved

csharp/extractor/Semmle.Extraction.CSharp/Entities/UserOperator.cs

@@ -2,6 +2,7 @@
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using System.IO;
 using System.Linq;
+using System.Text.RegularExpressions;
 
 namespace Semmle.Extraction.CSharp.Entities
 {
@@ -161,6 +162,9 @@ public static bool OperatorSymbol(string methodName, out string operatorName)
                 case "op_False":
                     operatorName = "false";
                     break;
+                case var @checked when Regex.IsMatch(@checked, "^op_Checked.*"):
+                    operatorName = @checked;
+                    break;
                 default:
                     operatorName = methodName;
                     success = false;