Fix interaction of C# 11 nint==IntPtr with overload resolution.

In C# 11+.NET 7 mode, we now always use type nint, never IntPtr, so that overload resolution works as expected.

ICSharpCode.Decompiler.Tests/PrettyTestRunner.cs

@@ -321,13 +321,11 @@ namespace ICSharpCode.Decompiler.Tests
 		[Test]
 		public async Task Loops([ValueSource(nameof(defaultOptionsWithMcs))] CompilerOptions cscOptions)
 		{
-			await RunForLibrary(cscOptions: cscOptions, decompilerSettings: new DecompilerSettings {
+			DecompilerSettings settings = Tester.GetSettings(cscOptions);
-				// legacy csc generates a dead store in debug builds
+			// legacy csc generates a dead store in debug builds
-				RemoveDeadStores = (cscOptions == CompilerOptions.None),
+			settings.RemoveDeadStores = (cscOptions == CompilerOptions.None);
-				UseExpressionBodyForCalculatedGetterOnlyProperties = false,
+			settings.UseExpressionBodyForCalculatedGetterOnlyProperties = false;
-				FileScopedNamespaces = false,
+			await RunForLibrary(cscOptions: cscOptions, decompilerSettings: settings);
-				NumericIntPtr = false,
-			});
 		}
 
 		[Test]

ICSharpCode.Decompiler.Tests/TestCases/Correctness/OverloadResolution.cs

@@ -36,6 +36,9 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Correctness
 			Issue1747();
 			CallAmbiguousOutParam();
 			CallWithInParam();
+#if CS90
+			NativeIntTests(new IntPtr(1), 2);
+#endif
 			Issue2444.M2();
 			Issue2741.B.Test(new Issue2741.C());
 		}
@@ -337,6 +340,34 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Correctness
 #endif
 		#endregion
 
+#if CS90
+		static void NativeIntTests(IntPtr i1, nint i2)
+		{
+			Console.WriteLine("NativeIntTests(i1):");
+			ObjectOrLong((object)i1);
+			ObjectOrLong((long)i1);
+			Console.WriteLine("NativeIntTests(i2):");
+			ObjectOrLong((object)i2);
+			ObjectOrLong((long)i2);
+			Console.WriteLine("NativeIntTests(new IntPtr):");
+			ObjectOrLong((object)new IntPtr(3));
+			ObjectOrLong((long)new IntPtr(3));
+			Console.WriteLine("NativeIntTests(IntPtr.Zero):");
+			ObjectOrLong((object)IntPtr.Zero);
+			ObjectOrLong((long)IntPtr.Zero);
+		}
+
+		static void ObjectOrLong(object o)
+		{
+			Console.WriteLine("object " + o);
+		}
+
+		static void ObjectOrLong(long l)
+		{
+			Console.WriteLine("long " + l);
+		}
+#endif
+
 		#region #2444
 		public struct Issue2444
 		{

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

@@ -93,20 +93,14 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 		[DllImport("ws2_32.dll", SetLastError = true)]
 		internal static extern nint ioctlsocket([In] nint socketHandle, [In] int cmd, [In][Out] ref int argp);
 
-		public void CallMethodWithInOutParameter()
-		{
-			int argp = 0;
-			ioctlsocket(nint.Zero, 0, ref argp);
-		}
 #else
 		[DllImport("ws2_32.dll", SetLastError = true)]
 		internal static extern IntPtr ioctlsocket([In] IntPtr socketHandle, [In] int cmd, [In][Out] ref int argp);
-
+#endif
 		public void CallMethodWithInOutParameter()
 		{
 			int argp = 0;
 			ioctlsocket(IntPtr.Zero, 0, ref argp);
 		}
-#endif
 	}
 }

ICSharpCode.Decompiler/CSharp/CallBuilder.cs

@@ -1553,12 +1553,25 @@ namespace ICSharpCode.Decompiler.CSharp
 					CastArguments(argumentList.Arguments, argumentList.ExpectedParameters);
 					break; // make sure that we don't not end up in an infinite loop
 				}
+				IType returnTypeOverride = null;
+				if (typeSystem.MainModule.TypeSystemOptions.HasFlag(TypeSystemOptions.NativeIntegersWithoutAttribute))
+				{
+					// For DeclaringType, we don't use nint/nuint (so that DeclaringType.GetConstructors etc. works),
+					// but in NativeIntegersWithoutAttribute mode we must use nint/nuint for expression types,
+					// so that the appropriate set of conversions is used for further overload resolution.
+					if (method.DeclaringType.IsKnownType(KnownTypeCode.IntPtr))
+						returnTypeOverride = SpecialType.NInt;
+					else if (method.DeclaringType.IsKnownType(KnownTypeCode.UIntPtr))
+						returnTypeOverride = SpecialType.NUInt;
+				}
 				return new ObjectCreateExpression(
 					expressionBuilder.ConvertType(method.DeclaringType),
 					argumentList.GetArgumentExpressions()
 				).WithRR(new CSharpInvocationResolveResult(
 					target, method, argumentList.GetArgumentResolveResults().ToArray(),
-					isExpandedForm: argumentList.IsExpandedForm, argumentToParameterMap: argumentList.ArgumentToParameterMap
+					isExpandedForm: argumentList.IsExpandedForm,
+					argumentToParameterMap: argumentList.ArgumentToParameterMap,
+					returnTypeOverride: returnTypeOverride
 				));
 			}
 		}

ICSharpCode.Decompiler/TypeSystem/MetadataModule.cs

@@ -402,8 +402,9 @@ namespace ICSharpCode.Decompiler.TypeSystem
 		IType ResolveDeclaringType(EntityHandle declaringTypeReference, GenericContext context)
 		{
 			// resolve without substituting dynamic/tuple types
-			var ty = ResolveType(declaringTypeReference, context,
+			const TypeSystemOptions removedOptions = TypeSystemOptions.Dynamic | TypeSystemOptions.Tuple
-				options & ~(TypeSystemOptions.Dynamic | TypeSystemOptions.Tuple | TypeSystemOptions.NullabilityAnnotations));
+				| TypeSystemOptions.NullabilityAnnotations | TypeSystemOptions.NativeIntegers | TypeSystemOptions.NativeIntegersWithoutAttribute;
+			var ty = ResolveType(declaringTypeReference, context, options & ~removedOptions);
 			// but substitute tuple types in type arguments:
 			ty = ApplyAttributeTypeVisitor.ApplyAttributesToType(ty, Compilation, null, metadata, options, Nullability.Oblivious, typeChildrenOnly: true);
 			return ty;

ICSharpCode.Decompiler/TypeSystem/TypeSystemExtensions.cs

@@ -239,7 +239,7 @@ namespace ICSharpCode.Decompiler.TypeSystem
 
 			bool IsUnmanagedTypeInternal(IType type)
 			{
-				if (type.Kind is TypeKind.Enum or TypeKind.Pointer or TypeKind.FunctionPointer)
+				if (type.Kind is TypeKind.Enum or TypeKind.Pointer or TypeKind.FunctionPointer or TypeKind.NInt or TypeKind.NUInt)
 				{
 					return true;
 				}