Add index based method to ILProcessor

This makes it simpler to work with it when the instruction positions
are known in advance.

Mono.Cecil.Cil/ILProcessor.cs

@@ -229,6 +229,16 @@ public void InsertAfter (Instruction target, Instruction instruction)
 			instructions.Insert (index + 1, instruction);
 		}
 
+		public void InsertAfter (int index, Instruction instruction)
+		{
+			if (index < 0 || index >= instructions.Count)
+				throw new ArgumentOutOfRangeException ("index");
+			if (instruction == null)
+				throw new ArgumentNullException ("instruction");
+
+			instructions.Insert (index + 1, instruction);
+		}
+
 		public void Append (Instruction instruction)
 		{
 			if (instruction == null)
@@ -248,6 +258,15 @@ public void Replace (Instruction target, Instruction instruction)
 			Remove (target);
 		}
 
+		public void Replace (int index, Instruction instruction)
+		{
+			if (instruction == null)
+				throw new ArgumentNullException ("instruction");
+
+			InsertAfter (index, instruction);
+			RemoveAt (index);
+		}
+
 		public void Remove (Instruction instruction)
 		{
 			if (instruction == null)
@@ -256,5 +275,13 @@ public void Remove (Instruction instruction)
 			if (!instructions.Remove (instruction))
 				throw new ArgumentOutOfRangeException ("instruction");
 		}
+
+		public void RemoveAt (int index)
+		{
+			if (index < 0 || index >= instructions.Count)
+				throw new ArgumentOutOfRangeException ("index");
+
+			instructions.RemoveAt (index);
+		}
 	}
 }

Test/Mono.Cecil.Tests/ILProcessorTests.cs

@@ -53,6 +53,30 @@ public void InsertAfter ()
 			AssertOpCodeSequence (new [] { OpCodes.Ldloc_0, OpCodes.Ldloc_1, OpCodes.Ldloc_2, OpCodes.Ldloc_3 }, method);
 		}
 
+		[Test]
+		public void InsertAfterUsingIndex ()
+		{
+			var method = CreateTestMethod (OpCodes.Ldloc_0, OpCodes.Ldloc_2, OpCodes.Ldloc_3);
+			var il = method.GetILProcessor ();
+
+			il.InsertAfter (
+				0,
+				il.Create (OpCodes.Ldloc_1));
+
+			AssertOpCodeSequence (new [] { OpCodes.Ldloc_0, OpCodes.Ldloc_1, OpCodes.Ldloc_2, OpCodes.Ldloc_3 }, method);
+		}
+
+		[Test]
+		public void ReplaceUsingIndex ()
+		{
+			var method = CreateTestMethod (OpCodes.Ldloc_0, OpCodes.Ldloc_2, OpCodes.Ldloc_3);
+			var il = method.GetILProcessor ();
+
+			il.Replace (1, il.Create (OpCodes.Nop));
+
+			AssertOpCodeSequence (new [] { OpCodes.Ldloc_0, OpCodes.Nop, OpCodes.Ldloc_3 }, method);
+		}
+
 		static void AssertOpCodeSequence (OpCode [] expected, MethodBody body)
 		{
 			var opcodes = body.Instructions.Select (i => i.OpCode).ToArray ();