Fix bug when decompiling lambdas that are nested 3 or more levels (and have a closure on each level).

ICSharpCode.Decompiler/Ast/Transforms/DelegateConstruction.cs

@@ -330,12 +330,30 @@ namespace ICSharpCode.Decompiler.Ast.Transforms
 						if (right is ThisReferenceExpression) {
 							isParameter = true;
 						} else if (right is IdentifierExpression) {
-							// handle parameters only if the whole method contains no other occurrance except for 'right'
+							// handle parameters only if the whole method contains no other occurrence except for 'right'
 							ILVariable v = right.Annotation<ILVariable>();
 							isParameter = v.IsParameter && parameterOccurrances.Count(c => c == v) == 1;
-							if (!isParameter && TypeAnalysis.IsSameType(v.Type, fieldDef.FieldType) && IsPotentialClosure(context, v.Type.ResolveWithinSameModule())) {
+							if (!isParameter && IsPotentialClosure(context, v.Type.ResolveWithinSameModule())) {
+								// parent display class within the same method
+								// (closure2.localsX = closure1;)
 								isDisplayClassParentPointerAssignment = true;
 							}
+						} else if (right is MemberReferenceExpression) {
+							// copy of parent display class reference from an outer lambda
+							// closure2.localsX = this.localsY
+							MemberReferenceExpression mre = m.Get<MemberReferenceExpression>("right").Single();
+							do {
+								// descend into the targets of the mre as long as the field types are closures
+								FieldDefinition fieldDef2 = mre.Annotation<FieldReference>().ResolveWithinSameModule();
+								if (fieldDef2 == null || !IsPotentialClosure(context, fieldDef2.FieldType.ResolveWithinSameModule())) {
+									break;
+								}
+								// if we finally get to a this reference, it's copying a display class parent pointer
+								if (mre.Target is ThisReferenceExpression) {
+									isDisplayClassParentPointerAssignment = true;
+								}
+								mre = mre.Target as MemberReferenceExpression;
+							} while (mre != null);
 						}
 						if (isParameter || isDisplayClassParentPointerAssignment) {
 							dict[fieldDef] = right;

ICSharpCode.Decompiler/Tests/DelegateConstruction.cs

@@ -25,22 +25,26 @@ public static class DelegateConstruction
 		
 		public Action CaptureOfThisAndParameterInForEach(int a)
 		{
-			foreach (var item in Enumerable.Empty<int>()) {
+			foreach (int item in Enumerable.Empty<int>()) {
+				if (item > 0) {
 					return delegate {
 						CaptureOfThisAndParameter(item + a);
 					};
 				}
+			}
 			return null;
 		}
 		
 		public Action CaptureOfThisAndParameterInForEachWithItemCopy(int a)
 		{
-			foreach (var item in Enumerable.Empty<int>()) {
+			foreach (int item in Enumerable.Empty<int>()) {
 				int copyOfItem = item;
+				if (item > 0) {
 					return delegate {
 						CaptureOfThisAndParameter(item + a + copyOfItem);
 					};
 				}
+			}
 			return null;
 		}
 	}
@@ -162,4 +166,9 @@ public static class DelegateConstruction
 	{
 		return b => c => a + b + c;
 	}
+	
+	public static Func<int, Func<int, Func<int, int>>> CurriedAddition2(int a)
+	{
+		return b => c => d => a + b + c + d;
+	}
 }