Added extension methods

IDEHelper/Tests/src/ExtensionMethods.bf

@@ -0,0 +1,59 @@
+using System;
+using System.Collections;
+
+using static Tests.ExtensionMethods.ClassB;
+
+namespace Tests
+{
+	class ExtensionMethods
+	{
+		public static int Remove(this String str, float val, float val2)
+		{
+			return 123;
+		}
+
+		class ClassA
+		{
+			public static void Test()
+			{
+				Test.Assert("Abc".Remove(1.2f, 2.3f) == 123);
+			}
+		}
+		
+		public class ClassB
+		{
+			public static int Flop(this String str, int a)
+			{
+				return a + 1000;
+			}
+
+		}
+
+		[Test]
+		public static void TestBasics()
+		{
+			ClassA.Test();
+
+			Test.Assert("Test".Flop(234) == 1234);
+
+			List<int> iList = scope .();
+			iList.Add(3);
+			iList.Add(20);
+			iList.Add(100);
+
+			Test.Assert(iList.Total() == 123);
+		}
+	}
+
+	static
+	{
+		public static T Total<T>(this List<T> list) where T : IOpAddable
+		{
+			T total = default;
+			for (let val in list)
+				total += val;
+			return total;
+		}
+	}
+}
+