Add VariableScope and rework AssignVariableNames step to support renaming parameters of nested ILFunctions in the future.

Author: siegfriedpammer

ICSharpCode.Decompiler.Tests/TestCases/Pretty/DelegateConstruction.cs

@@ -377,10 +377,10 @@ public static void NameConflict()
 		public static void NameConflict2(int j)
 		{
 			List<Action<int>> list = new List<Action<int>>();
-			for (int k = 0; k < 10; k++)
+			for (int i = 0; i < 10; i++)
 			{
-				list.Add(delegate (int i) {
-					Console.WriteLine(i);
+				list.Add(delegate (int k) {
+					Console.WriteLine(k);
 				});
 			}
 		}

ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs

@@ -2547,15 +2547,18 @@ IEnumerable<ParameterDeclaration> MakeParameters(IReadOnlyList<IParameter> param
 			foreach (var parameter in parameters)
 			{
 				var pd = astBuilder.ConvertParameter(parameter);
+				if (variables.TryGetValue(i, out var v))
+				{
+					pd.AddAnnotation(new ILVariableResolveResult(v, parameters[i].Type));
+					pd.Name = v.Name;
+				}
 				if (string.IsNullOrEmpty(pd.Name) && !pd.Type.IsArgList())
 				{
 					// needs to be consistent with logic in ILReader.CreateILVarable(ParameterDefinition)
 					pd.Name = "P_" + i;
 				}
 				if (settings.AnonymousTypes && parameter.Type.ContainsAnonymousType())
 					pd.Type = null;
-				if (variables.TryGetValue(i, out var v))
-					pd.AddAnnotation(new ILVariableResolveResult(v, parameters[i].Type));
 				yield return pd;
 				i++;
 			}

ICSharpCode.Decompiler/CSharp/StatementBuilder.cs

@@ -1389,6 +1389,16 @@ LocalFunctionDeclarationStatement TranslateFunction(ILFunction function)
 				var astBuilder = exprBuilder.astBuilder;
 				var method = (MethodDeclaration)astBuilder.ConvertEntity(function.ReducedMethod);
 
+				var variables = function.Variables.Where(v => v.Kind == VariableKind.Parameter).ToDictionary(v => v.Index);
+
+				foreach (var (i, p) in method.Parameters.WithIndex())
+				{
+					if (variables.TryGetValue(i, out var v))
+					{
+						p.Name = v.Name;
+					}
+				}
+
 				if (function.Method.HasBody)
 				{
 					var nestedBuilder = new StatementBuilder(

ICSharpCode.Decompiler/IL/ControlFlow/AsyncAwaitDecompiler.cs

@@ -1165,6 +1165,7 @@ void InlineBodyOfMoveNext(ILFunction function)
 			function.MoveNextMethod = moveNextFunction.Method;
 			function.SequencePointCandidates = moveNextFunction.SequencePointCandidates;
 			function.CodeSize = moveNextFunction.CodeSize;
+			function.LocalVariableSignatureLength = moveNextFunction.LocalVariableSignatureLength;
 			function.IsIterator = IsAsyncEnumerator;
 			moveNextFunction.Variables.Clear();
 			moveNextFunction.ReleaseRef();

ICSharpCode.Decompiler/IL/ControlFlow/YieldReturnDecompiler.cs

@@ -656,6 +656,7 @@ BlockContainer AnalyzeMoveNext(ILFunction function)
 			function.MoveNextMethod = moveNextFunction.Method;
 			function.SequencePointCandidates = moveNextFunction.SequencePointCandidates;
 			function.CodeSize = moveNextFunction.CodeSize;
+			function.LocalVariableSignatureLength = moveNextFunction.LocalVariableSignatureLength;
 
 			// Copy-propagate temporaries holding a copy of 'this'.
 			// This is necessary because the old (pre-Roslyn) C# compiler likes to store 'this' in temporary variables.

ICSharpCode.Decompiler/IL/ILReader.cs

@@ -342,7 +342,10 @@ ILVariable CreateILVariable(int index, IType parameterType, string name)
 			if (index < 0)
 				ilVar.Name = "this";
 			else if (string.IsNullOrWhiteSpace(name))
+			{
 				ilVar.Name = "P_" + index;
+				ilVar.HasGeneratedName = true;
+			}
 			else
 				ilVar.Name = name;
 			return ilVar;
@@ -706,6 +709,7 @@ public ILFunction ReadIL(MethodDefinitionHandle method, MethodBodyBlock body, Ge
 			var function = new ILFunction(this.method, body.GetCodeSize(), this.genericContext, mainContainer, kind);
 			function.Variables.AddRange(parameterVariables);
 			function.Variables.AddRange(localVariables);
+			function.LocalVariableSignatureLength = localVariables.Length;
 			Debug.Assert(stackVariables != null);
 			function.Variables.AddRange(stackVariables);
 			function.Variables.AddRange(variableByExceptionHandler.Values);

ICSharpCode.Decompiler/IL/Instructions/ILFunction.cs

@@ -67,6 +67,11 @@ partial class ILFunction
 		/// </summary>
 		public readonly ILVariableCollection Variables;
 
+		/// <summary>
+		/// Gets 
+		/// </summary>
+		public int LocalVariableSignatureLength;
+
 		/// <summary>
 		/// Gets the scope in which the local function is declared.
 		/// Returns null, if this is not a local function.