From 8323eb79b876ce106ce831d6d7da60b40cf9a22e Mon Sep 17 00:00:00 2001
From: Siegfried Pammer <siegfriedpammer@gmail.com>
Date: Sun, 22 Jun 2025 08:23:47 +0200
Subject: [PATCH] Add support for newobj ROS(in arg) to
 TransformParamsArgument.

---
 ICSharpCode.Decompiler/CSharp/CallBuilder.cs | 79 +++++++++++---------
 1 file changed, 42 insertions(+), 37 deletions(-)

diff --git a/ICSharpCode.Decompiler/CSharp/CallBuilder.cs b/ICSharpCode.Decompiler/CSharp/CallBuilder.cs
index 058eff4e3..5efb802ee 100644
--- a/ICSharpCode.Decompiler/CSharp/CallBuilder.cs
+++ b/ICSharpCode.Decompiler/CSharp/CallBuilder.cs
@@ -1026,25 +1026,14 @@ namespace ICSharpCode.Decompiler.CSharp
 		}
 
 		private bool TransformParamsArgument(ExpectedTargetDetails expectedTargetDetails, ResolveResult targetResolveResult,
-			IMethod method, IParameter parameter, TranslatedExpression arg, ref List<IParameter> expectedParameters,
+			IMethod method, IParameter parameter, TranslatedExpression paramsArgument, ref List<IParameter> expectedParameters,
 			ref List<TranslatedExpression> arguments)
 		{
-			if (CheckArgument(out int length, out IType elementType))
+			var expressionBuilder = this.expressionBuilder;
+			if (ExtractArguments(out IType elementType, out var expandedParameters, out var expandedArguments))
 			{
-				var expandedParameters = new List<IParameter>(expectedParameters);
-				var expandedArguments = new List<TranslatedExpression>(arguments);
-				if (length > 0)
-				{
-					var arrayElements = ((ArrayCreateExpression)arg.Expression).Initializer.Elements.ToArray();
-					for (int j = 0; j < length; j++)
-					{
-						expandedParameters.Add(new DefaultParameter(elementType, parameter.Name + j));
-						if (j < arrayElements.Length)
-							expandedArguments.Add(new TranslatedExpression(arrayElements[j]));
-						else
-							expandedArguments.Add(expressionBuilder.GetDefaultValueExpression(elementType).WithoutILInstruction());
-					}
-				}
+				expandedParameters.InsertRange(0, expectedParameters);
+				expandedArguments.InsertRange(0, arguments);
 				if (IsUnambiguousCall(expectedTargetDetails, method, targetResolveResult, Empty<IType>.Array,
 					expandedArguments.SelectArray(a => a.ResolveResult), argumentNames: null,
 					firstOptionalArgumentIndex: -1, out _,
@@ -1057,30 +1046,46 @@ namespace ICSharpCode.Decompiler.CSharp
 			}
 			return false;
 
-			bool CheckArgument(out int len, out IType t)
+			bool ExtractArguments(out IType elementType, out List<IParameter> parameters, out List<TranslatedExpression> arguments)
 			{
-				len = 0;
-				t = null;
-				if (arg.ResolveResult is CSharpInvocationResolveResult csirr &&
-					csirr.Arguments.Count == 0 && csirr.Member is IMethod emptyMethod &&
-					emptyMethod.IsStatic &&
-					"System.Array.Empty" == emptyMethod.FullName &&
-					emptyMethod.TypeArguments.Count == 1)
+				elementType = null;
+				parameters = null;
+				arguments = null;
+				switch (paramsArgument.ResolveResult)
 				{
-					t = emptyMethod.TypeArguments[0];
-					return true;
-				}
-
-				if (arg.ResolveResult is ArrayCreateResolveResult acrr &&
-					acrr.SizeArguments.Count == 1 &&
-					acrr.SizeArguments[0].IsCompileTimeConstant &&
-					acrr.SizeArguments[0].ConstantValue is int l)
-				{
-					len = l;
-					t = ((ArrayType)acrr.Type).ElementType;
-					return true;
+					case CSharpInvocationResolveResult { Member: IMethod method, Arguments: var args }:
+						// match System.Array.Empty<T>()
+						if (args is [] && method is { IsStatic: true, FullName: "System.Array.Empty", TypeArguments: [var type] })
+						{
+							elementType = type;
+							arguments = new();
+							parameters = new();
+							return true;
+						}
+						if (paramsArgument.Expression is ObjectCreateExpression oce
+							&& method is { IsConstructor: true, DeclaringType: { TypeArguments: [var type2] } declaringType }
+							&& declaringType.IsKnownType(KnownTypeCode.ReadOnlySpanOfT))
+						{
+							elementType = type2;
+							arguments = new() { new TranslatedExpression(oce.Arguments.Single()) };
+							parameters = new() { new DefaultParameter(type2, string.Empty) };
+							return true;
+						}
+						return false;
+					case ArrayCreateResolveResult { Type: ArrayType { ElementType: var type3 }, SizeArguments: [{ ConstantValue: int arrayLength }] }:
+						elementType = type3;
+						arguments = new(((ArrayCreateExpression)paramsArgument.Expression).Initializer.Elements.Select(e => new TranslatedExpression(e)));
+						parameters = new List<IParameter>(arrayLength);
+						for (int i = 0; i < arrayLength; i++)
+						{
+							parameters.Add(new DefaultParameter(type3, string.Empty));
+							if (arguments.Count <= i)
+								arguments.Add(new TranslatedExpression(expressionBuilder.GetDefaultValueExpression(type3).WithoutILInstruction()));
+						}
+						return true;
+					default:
+						return false;
 				}
-				return false;
 			}
 		}