C#: Adjust the extractor to correctly handle names for user defined increment and decrement operators.

Author: michaelnebel

csharp/extractor/Semmle.Extraction.CSharp.Util/SymbolExtensions.cs

@@ -52,6 +52,13 @@ public static string GetName(this ISymbol symbol, bool useMetadataName = false)
             { "op_False", "false" }
         });
 
+        /// <summary>
+        /// The operatorname for user-defined increment and decrement operators are "op_IncrementAssignment" and
+        /// "op_DecrementAssignment" respectively.
+        /// Thus we need to handle this explicitly to avoid postfixing them with an "=".
+        /// </summary>
+        private static bool isIncrementOrDecrement(string operatorName) => operatorName == "++" || operatorName == "--";
+
         /// <summary>
         /// Convert an operator method name in to a symbolic name.
         /// A return value indicates whether the conversion succeeded.
@@ -72,7 +79,7 @@ public static bool TryGetOperatorSymbol(this ISymbol symbol, out string operator
             if (match.Success && methodToOperator.TryGetValue($"op_{match.Groups[2]}", out var rawOperatorName))
             {
                 var prefix = match.Groups[1].Success ? "checked " : "";
-                var postfix = match.Groups[3].Success ? "=" : "";
+                var postfix = match.Groups[3].Success && !isIncrementOrDecrement(rawOperatorName) ? "=" : "";
                 operatorName = $"{prefix}{rawOperatorName}{postfix}";
                 return true;
             }