Add HasGeneratedName flag

ICSharpCode.Decompiler/IL/ILReader.cs

@@ -128,10 +128,15 @@ namespace ICSharpCode.Decompiler.IL
 		{
 			VariableKind kind = v.IsPinned ? VariableKind.PinnedLocal : VariableKind.Local;
 			ILVariable ilVar = new ILVariable(kind, typeSystem.Resolve(v.VariableType), v.Index);
-			if (!UseDebugSymbols || debugInfo == null || !debugInfo.TryGetName(v, out string name))
+			if (!UseDebugSymbols || debugInfo == null || !debugInfo.TryGetName(v, out string name)) {
 				ilVar.Name = "V_" + v.Index;
-			else
-				ilVar.Name = !string.IsNullOrWhiteSpace(name) ? name : "V_" + v.Index;
+				ilVar.HasGeneratedName = true;
+			} else if (string.IsNullOrWhiteSpace(name)) {
+				ilVar.Name = "V_" + v.Index;
+				ilVar.HasGeneratedName = true;
+			} else {
+				ilVar.Name = name;
+			}
 			return ilVar;
 		}
 

ICSharpCode.Decompiler/IL/ILVariable.cs

@@ -91,6 +91,8 @@ namespace ICSharpCode.Decompiler.IL
 		
 		public string Name { get; set; }
 
+		public bool HasGeneratedName { get; set; }
+
 		/// <summary>
 		/// Gets the function in which this variable is declared.
 		/// </summary>

ICSharpCode.Decompiler/IL/Instructions/ILFunction.cs

@@ -127,6 +127,7 @@ namespace ICSharpCode.Decompiler.IL
 		public ILVariable RegisterVariable(VariableKind kind, IType type, string name = null)
 		{
 			int index = Variables.Where(v => v.Kind == kind).MaxOrDefault(v => v.Index, -1) + 1;
+			var variable = new ILVariable(kind, type, index);
 			if (string.IsNullOrWhiteSpace(name)) {
 				switch (kind) {
 					case VariableKind.Local:
@@ -145,8 +146,8 @@ namespace ICSharpCode.Decompiler.IL
 						throw new NotSupportedException();
 				}
 				name += index;
+				variable.HasGeneratedName = true;
 			}
-			var variable = new ILVariable(kind, type, index);
 			variable.Name = name;
 			Variables.Add(variable);
 			return variable;

ICSharpCode.Decompiler/IL/Transforms/AssignVariableNames.cs

@@ -59,6 +59,8 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			this.context = context;
 			currentFieldNames = function.Method.DeclaringType.Fields.Select(f => f.Name).ToArray();
 			reservedVariableNames = new Dictionary<string, int>();
+			foreach (var p in function.Descendants.OfType<ILFunction>().Select(f => f.Method).SelectMany(m => m.Parameters))
+				AddExistingName(p.Name);
 			foreach (ILFunction f in function.Descendants.OfType<ILFunction>().Reverse()) {
 				PerformAssignment(f);
 			}
@@ -66,27 +68,21 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 
 		void PerformAssignment(ILFunction function)
 		{
-			foreach (var p in function.Method.Parameters)
-				AddExistingName(p.Name);
 			foreach (var v in function.Variables) {
 				switch (v.Kind) {
-					case VariableKind.Parameter:
+					case VariableKind.Parameter: // ignore
+						break;
 					case VariableKind.StackSlot: // keep generated names
 						AddExistingName(v.Name);
 						break;
 					default:
-						string varName = v.Name;
-						if (context.Settings.UseDebugSymbols) {
-							if (string.IsNullOrEmpty(varName) || varName.StartsWith("V_", StringComparison.Ordinal) || !IsValidName(varName)) {
+						if (v.HasGeneratedName || !IsValidName(v.Name)) {
 							// don't use the name from the debug symbols if it looks like a generated name
 							v.Name = null;
 						} else {
 							// use the name from the debug symbols
 							// (but ensure we don't use the same name for two variables)
-								v.Name = GetAlternativeName(varName);
-							}
-						} else {
-							v.Name = null;
+							v.Name = GetAlternativeName(v.Name);
 						}
 						break;
 				}

ICSharpCode.Decompiler/IL/Transforms/SplitVariables.cs

@@ -97,6 +97,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 				if (!newVariables.TryGetValue(representative, out v)) {
 					v = new ILVariable(inst.Variable.Kind, inst.Variable.Type, inst.Variable.StackType, inst.Variable.Index);
 					v.Name = inst.Variable.Name;
+					v.HasGeneratedName = inst.Variable.HasGeneratedName;
 					v.StateMachineField = inst.Variable.StateMachineField;
 					v.HasInitialValue = false; // we'll set HasInitialValue when we encounter an uninit load
 					newVariables.Add(representative, v);