C#: Add extractor support for using different expression kinds for NOT expressions.

Author: michaelnebel

csharp/extractor/Semmle.Extraction.CSharp/Entities/Expressions/Factory.cs

@@ -146,7 +146,7 @@ internal static Expression Create(ExpressionNodeInfo info)
                         return Name.Create(info);
 
                     case SyntaxKind.LogicalNotExpression:
-                        return PrefixUnary.Create(info.SetKind(ExprKind.LOG_NOT));
+                        return Not.Create(info);
 
                     case SyntaxKind.BitwiseNotExpression:
                         return PrefixUnary.Create(info.SetKind(ExprKind.BIT_NOT));

csharp/extractor/Semmle.Extraction.CSharp/Entities/Expressions/Not.cs

@@ -0,0 +1,19 @@
+using Microsoft.CodeAnalysis;
+using Semmle.Extraction.Kinds;
+
+namespace Semmle.Extraction.CSharp.Entities.Expressions
+{
+    internal static class Not
+    {
+        public static Expression Create(ExpressionNodeInfo info)
+        {
+            var cx = info.Context;
+            if (cx.GetSymbolInfo(info.Node).Symbol is IMethodSymbol @operator &&
+               @operator.MethodKind == MethodKind.BuiltinOperator)
+            {
+                return PrefixUnary.Create(info.SetKind(ExprKind.LOG_NOT));
+            }
+            return PrefixUnary.Create(info.SetKind(ExprKind.NOT));
+        }
+    }
+}

csharp/extractor/Semmle.Extraction.CSharp/Entities/Expressions/PrefixUnary.cs

@@ -11,7 +11,6 @@ private PrefixUnary(ExpressionNodeInfo info)
         {
         }
 
-
         public static Expression Create(ExpressionNodeInfo info) => new PrefixUnary(info).TryPopulate();
 
         protected override void PopulateExpression(TextWriter trapFile)