code generations for unary operators

Compiler/Generator/NotSpecifiedException.cs

@@ -0,0 +1,21 @@
+using System;
+using Compiler.Lexer;
+using Compiler.Parser.Nodes;
+
+namespace Compiler.Generator
+{
+    public class NotSpecifiedException : Exception
+    {
+        public override string Message { get; }
+
+        public NotSpecifiedException(NodeType nodeType)
+        {
+            Message = $"No code generation for {nodeType} specified.";
+        }
+
+        public NotSpecifiedException(NodeType nodeType, OperatorType operatorType)
+        {
+            Message = $"No code generation for {nodeType}:{operatorType} specified.";
+        }
+    }
+}