Extend CompoundAssignment-transformation to ldelema patterns

ICSharpCode.Decompiler/IL/Transforms/ExpressionTransforms.cs

@@ -202,9 +202,13 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 		bool IsSameTarget(ILInstruction target, ILInstruction left)
 		{
 			IField f, f2;
-			ILInstruction t, t2;
+			ILInstruction t, t2, a, a2;
+			IType type, type2;
 			if (target.MatchLdFlda(out t, out f) && left.MatchLdFlda(out t2, out f2) && f.Equals(f2))
 				return true;
+			// match ldelmena(ldobj(...))
+			if (target.MatchLdElema(out type, out a) && left.MatchLdElema(out type2, out a2) && type.Equals(type2))
+				return a.MatchLdObj(out target, out type) && a2.MatchLdObj(out left, out type2) && IsSameTarget(target, left);
 			return false;
 		}