Add steps for transforms.

ICSharpCode.Decompiler/IL/Instructions/ILFunction.cs

@@ -82,7 +82,9 @@ namespace ICSharpCode.Decompiler.IL
 			this.CheckInvariant(ILPhase.Normal);
 			foreach (var transform in transforms) {
 				context.CancellationToken.ThrowIfCancellationRequested();
+				context.Stepper.StartGroup(transform.GetType().Name);
 				transform.Run(this, context);
+				context.Stepper.EndGroup(keepIfEmpty: true);
 				this.CheckInvariant(ILPhase.Normal);
 			}
 		}

ICSharpCode.Decompiler/IL/Transforms/Stepper.cs

@@ -18,6 +18,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
@@ -60,7 +61,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			public ILInstruction Position { get; set; }
 			public int Step { get; set; }
 
-			public ICollection<Node> Children { get; } = new List<Node>();
+			public IList<Node> Children { get; } = new List<Node>();
 		}
 
 		readonly Stack<Node> groups;
@@ -79,7 +80,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 		/// 
 		/// May throw <see cref="StepLimitReachedException"/> in debug mode.
 		/// </summary>
-		public void Step(string description, ILInstruction near)
+		public void Step(string description, ILInstruction near = null)
 		{
 			StepInternal(description, near);
 		}
@@ -88,7 +89,11 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 		{
 			if (step >= StepLimit)
 				throw new StepLimitReachedException();
-			var stepNode = new Node { Description = $"{description} ({step})", Position = near, Step = step };
+			var stepNode = new Node {
+				Description = $"{step}: {description}",
+				Position = near,
+				Step = step
+			};
 			var p = groups.PeekOrDefault();
 			if (p != null)
 				p.Children.Add(stepNode);
@@ -98,14 +103,19 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			return stepNode;
 		}
 
-		public void StartGroup(string description, ILInstruction near)
+		public void StartGroup(string description, ILInstruction near = null)
 		{
 			groups.Push(StepInternal(description, near));
 		}
 
-		public void EndGroup()
+		public void EndGroup(bool keepIfEmpty = false)
 		{
-			groups.Pop();
+			var node = groups.Pop();
+			if (!keepIfEmpty && node.Children.Count == 0) {
+				var col = groups.PeekOrDefault()?.Children ?? steps;
+				Debug.Assert(col.Last() == node);
+				col.RemoveAt(col.Count - 1);
+			}
 		}
 	}
 }

ILSpy/Languages/ILAstLanguage.cs

@@ -99,20 +99,7 @@ namespace ICSharpCode.ILSpy
 		{
 			yield return new TypedIL();
 			CSharpDecompiler decompiler = new CSharpDecompiler(ModuleDefinition.CreateModule("Dummy", ModuleKind.Dll), new DecompilerSettings());
-			for (int i = 0; i <= decompiler.ILTransforms.Count; i++) {
-				yield return MakeDebugLanguage(decompiler.ILTransforms.Take(i));
-				var loop = decompiler.ILTransforms.ElementAtOrDefault(i) as LoopingTransform;
-				if (loop != null) {
-					for (int j = 1; j <= loop.Transforms.Count; j++) {
-						yield return MakeDebugLanguage(decompiler.ILTransforms.Take(i).Concat(loop.Transforms.Take(j)));
-					}
-				}
-			}
-		}
-
-		static ILAstLanguage MakeDebugLanguage(IEnumerable<IILTransform> transforms)
-		{
-			return new BlockIL(transforms.ToList());
+			yield return new BlockIL(decompiler.ILTransforms.ToList());
 		}
 		
 		public override string FileExtension {
@@ -155,7 +142,7 @@ namespace ICSharpCode.ILSpy
 		{
 			readonly IReadOnlyList<IILTransform> transforms;
 			
-			public BlockIL(IReadOnlyList<IILTransform> transforms) : base(transforms.Count == 0 ? "ILAst (blocks)" :  "ILAst (" + transforms.Last().GetType().Name + ")")
+			public BlockIL(IReadOnlyList<IILTransform> transforms) : base("ILAst")
 			{
 				this.transforms = transforms;
 			}
@@ -170,6 +157,8 @@ namespace ICSharpCode.ILSpy
 				ILFunction il = reader.ReadIL(method.Body, options.CancellationToken);
 				ILTransformContext context = new ILTransformContext { Settings = options.DecompilerSettings, TypeSystem = typeSystem };
 				context.Stepper.StepLimit = options.StepLimit;
+				// Because the UI only allows viewing the result of a step, add a dummy initial step.
+				context.Stepper.Step("Initial");
 				try {
 					il.RunTransforms(transforms, context);
 				} catch (StepLimitReachedException) {