Use Nop instead of InvalidExpression to hold the "goto from catch-block to try-block" comment

ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs

@@ -4408,7 +4408,7 @@ namespace ICSharpCode.Decompiler.CSharp
 
 		protected internal override TranslatedExpression VisitInvalidExpression(InvalidExpression inst, TranslationContext context)
 		{
-			string message = inst.Severity;
+			string message = "Error";
 			if (inst.StartILOffset != 0)
 			{
 				message += $" near IL_{inst.StartILOffset:x4}";

ICSharpCode.Decompiler/IL/BlockBuilder.cs

@@ -385,7 +385,7 @@ namespace ICSharpCode.Decompiler.IL
 				}
 				var usedLabels = new LongSet(dispatch.TargetILOffsets.Select(offset => LongInterval.Inclusive(offset, offset)));
 				switchInst.Sections.Add(new SwitchSection { Labels = usedLabels.Invert(), Body = new Branch(tryBody.EntryPoint) });
-				dispatchBlock.Instructions.Add(new InvalidExpression("ILSpy has introduced the following switch to emulate a goto from catch-block to try-block") { Severity = "Note" });
+				dispatchBlock.Instructions.Add(new Nop { Comment = "ILSpy has introduced the following switch to emulate a goto from catch-block to try-block" });
 				dispatchBlock.Instructions.Add(switchInst);
 
 				tryBody.Blocks.Insert(0, dispatchBlock);

ICSharpCode.Decompiler/IL/ControlFlow/ControlFlowSimplification.cs

@@ -15,7 +15,6 @@
 // FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
 // OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 // DEALINGS IN THE SOFTWARE.
-using System;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
@@ -71,7 +70,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 			}
 
 			// Remove 'nop' instructions
-			block.Instructions.RemoveAll(inst => inst.OpCode == OpCode.Nop);
+			block.Instructions.RemoveAll(inst => inst is Nop { Comment: null });
 		}
 
 		private static void RemoveDeadStackStores(Block block, ILTransformContext context)

ICSharpCode.Decompiler/IL/Instructions/SimpleInstruction.cs

@@ -89,7 +89,6 @@ namespace ICSharpCode.Decompiler.IL
 
 	partial class InvalidExpression : SimpleInstruction
 	{
-		public string Severity = "Error";
 		public string? Message;
 		public StackType ExpectedResultType = StackType.Unknown;