C#: Add a QL class for UnaryNotOperation.

Author: michaelnebel

csharp/ql/lib/semmle/code/csharp/exprs/Expr.qll

@@ -243,6 +243,24 @@ class UnaryCallOperation extends OperatorCall, UnaryOperation, @un_op_call_expr
   override string toString() { result = UnaryOperation.super.toString() }
 }
 
+/**
+ * A logical 'not', for example `!String.IsNullOrEmpty(s)` or a call to a user-defined
+ * not operator such as `!x` in:
+ * ```csharp
+ * class Negatable {
+ *   public static Negatable operator !(Negatable n) => { ...};
+ * }
+ *
+ * var x = new Negatable();
+ * var y = !x;
+ * ```
+ */
+class UnaryNotOperation extends UnaryCallOperation, @un_not_op_expr {
+  override string getOperator() { result = "!" }
+
+  override string getAPrimaryQlClass() { result = "UnaryNotOperation" }
+}
+
 /**
  * A binary operation. Either a binary arithmetic operation
  * (`BinaryArithmeticOperation`), a binary bitwise operation

csharp/ql/lib/semmle/code/csharp/exprs/LogicalOperation.qll

@@ -23,8 +23,8 @@ class UnaryLogicalOperation extends LogicalOperation, UnaryCallOperation, @un_lo
 /**
  * A logical 'not', for example `!String.IsNullOrEmpty(s)`.
  */
-class LogicalNotExpr extends UnaryLogicalOperation, @log_not_expr {
-  override string getOperator() { result = "!" }
+class LogicalNotExpr extends UnaryLogicalOperation, UnaryNotOperation, @log_not_expr {
+  override string getOperator() { result = UnaryNotOperation.super.getOperator() }
 
   override string getAPrimaryQlClass() { result = "LogicalNotExpr" }
 }