Add support for arithmetic using C# 9 native integer types.

ICSharpCode.Decompiler.Tests/TestCases/ILPretty/Unsafe.cs

@@ -186,7 +186,7 @@ namespace System.Runtime.CompilerServices
 		[MethodImpl(MethodImplOptions.AggressiveInlining)]
 		public unsafe static void* Add<T>(void* source, int elementOffset)
 		{
-			return (byte*)source + (long)elementOffset * (long)sizeof(T);
+			return (byte*)source + (nint)elementOffset * (nint)sizeof(T);
 		}
 
 		[MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -210,7 +210,7 @@ namespace System.Runtime.CompilerServices
 		[MethodImpl(MethodImplOptions.AggressiveInlining)]
 		public unsafe static void* Subtract<T>(void* source, int elementOffset)
 		{
-			return (byte*)source - (long)elementOffset * (long)sizeof(T);
+			return (byte*)source - (nint)elementOffset * (nint)sizeof(T);
 		}
 
 		[MethodImpl(MethodImplOptions.AggressiveInlining)]

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

@@ -73,5 +73,30 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 			u64 = (uint)i;
 			i = (nint)u64;
 		}
+
+		public void Arithmetic()
+		{
+			Console.WriteLine((nint)intptr * 2);
+			Console.WriteLine(i * 2);
+
+			Console.WriteLine(i + (nint)u);
+			Console.WriteLine((nuint)i + u);
+		}
+
+		public object[] Boxing()
+		{
+			return new object[10] {
+				1,
+				(nint)2,
+				3L,
+				4u,
+				(nuint)5u,
+				6uL,
+				int.MaxValue,
+				(nint)int.MaxValue,
+				i64,
+				(nint)i64
+			};
+		}
 	}
 }

ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs

@@ -109,15 +109,10 @@ namespace ICSharpCode.Decompiler.CSharp
 			if (!allowImplicitConversion) {
 				if (expr is NullReferenceExpression && rr.Type.Kind != TypeKind.Null) {
 					expr = new CastExpression(ConvertType(rr.Type), expr);
-				} else {
+				} else if (rr.Type.IsCSharpSmallIntegerType()) {
-					switch (rr.Type.GetDefinition()?.KnownTypeCode) {
-						case KnownTypeCode.SByte:
-						case KnownTypeCode.Byte:
-						case KnownTypeCode.Int16:
-						case KnownTypeCode.UInt16:
 					expr = new CastExpression(new PrimitiveType(KnownTypeReference.GetCSharpNameByTypeCode(rr.Type.GetDefinition().KnownTypeCode)), expr);
-							break;
+				} else if (rr.Type.IsCSharpNativeIntegerType()) {
-					}
+					expr = new CastExpression(new PrimitiveType(rr.Type.Name), expr);
 				}
 			}
 			var exprRR = expr.Annotation<ResolveResult>();
@@ -900,24 +895,14 @@ namespace ICSharpCode.Decompiler.CSharp
 				}
 			}
 
+			if (inst.InputType.IsIntegerType()) {
 				// Ensure the inputs have the correct sign:
-			KnownTypeCode inputType = KnownTypeCode.None;
+				IType inputType = FindArithmeticType(inst.InputType, inst.Sign);
-			switch (inst.InputType) {
-				case StackType.I: // In order to generate valid C# we need to treat (U)IntPtr as (U)Int64 in comparisons.
-				case StackType.I8:
-					inputType = inst.Sign == Sign.Unsigned ? KnownTypeCode.UInt64 : KnownTypeCode.Int64;
-					break;
-				case StackType.I4:
-					inputType = inst.Sign == Sign.Unsigned ? KnownTypeCode.UInt32 : KnownTypeCode.Int32;
-					break;
-			}
-			if (inputType != KnownTypeCode.None) {
-				IType targetType = compilation.FindType(inputType);
 				if (inst.IsLifted) {
-					targetType = NullableType.Create(compilation, targetType);
+					inputType = NullableType.Create(compilation, inputType);
 				}
-				left = left.ConvertTo(targetType, this);
+				left = left.ConvertTo(inputType, this);
-				right = right.ConvertTo(targetType, this);
+				right = right.ConvertTo(inputType, this);
 			}
 			return new BinaryOperatorExpression(left.Expression, op, right.Expression)
 				.WithILInstruction(inst)
@@ -993,22 +978,22 @@ namespace ICSharpCode.Decompiler.CSharp
 		{
 			switch (inst.Operator) {
 				case BinaryNumericOperator.Add:
-					return HandleBinaryNumeric(inst, BinaryOperatorType.Add);
+					return HandleBinaryNumeric(inst, BinaryOperatorType.Add, context);
 				case BinaryNumericOperator.Sub:
-					return HandleBinaryNumeric(inst, BinaryOperatorType.Subtract);
+					return HandleBinaryNumeric(inst, BinaryOperatorType.Subtract, context);
 				case BinaryNumericOperator.Mul:
-					return HandleBinaryNumeric(inst, BinaryOperatorType.Multiply);
+					return HandleBinaryNumeric(inst, BinaryOperatorType.Multiply, context);
 				case BinaryNumericOperator.Div:
 					return HandlePointerSubtraction(inst)
-						?? HandleBinaryNumeric(inst, BinaryOperatorType.Divide);
+						?? HandleBinaryNumeric(inst, BinaryOperatorType.Divide, context);
 				case BinaryNumericOperator.Rem:
-					return HandleBinaryNumeric(inst, BinaryOperatorType.Modulus);
+					return HandleBinaryNumeric(inst, BinaryOperatorType.Modulus, context);
 				case BinaryNumericOperator.BitAnd:
-					return HandleBinaryNumeric(inst, BinaryOperatorType.BitwiseAnd);
+					return HandleBinaryNumeric(inst, BinaryOperatorType.BitwiseAnd, context);
 				case BinaryNumericOperator.BitOr:
-					return HandleBinaryNumeric(inst, BinaryOperatorType.BitwiseOr);
+					return HandleBinaryNumeric(inst, BinaryOperatorType.BitwiseOr, context);
 				case BinaryNumericOperator.BitXor:
-					return HandleBinaryNumeric(inst, BinaryOperatorType.ExclusiveOr);
+					return HandleBinaryNumeric(inst, BinaryOperatorType.ExclusiveOr, context);
 				case BinaryNumericOperator.ShiftLeft:
 					return HandleShift(inst, BinaryOperatorType.ShiftLeft);
 				case BinaryNumericOperator.ShiftRight:
@@ -1158,7 +1143,7 @@ namespace ICSharpCode.Decompiler.CSharp
 
 		TranslatedExpression EnsureIntegerType(TranslatedExpression expr)
 		{
-			if (!expr.Type.IsCSharpPrimitiveIntegerType()) {
+			if (!expr.Type.IsCSharpPrimitiveIntegerType() && !expr.Type.IsCSharpNativeIntegerType()) {
 				// pointer arithmetic accepts all primitive integer types, but no enums etc.
 				StackType targetType = expr.Type.GetStackType() == StackType.I4 ? StackType.I4 : StackType.I8;
 				expr = expr.ConvertTo(
@@ -1254,7 +1239,7 @@ namespace ICSharpCode.Decompiler.CSharp
 			}
 		}
 		
-		TranslatedExpression HandleBinaryNumeric(BinaryNumericInstruction inst, BinaryOperatorType op)
+		TranslatedExpression HandleBinaryNumeric(BinaryNumericInstruction inst, BinaryOperatorType op, TranslationContext context)
 		{
 			var resolverWithOverflowCheck = resolver.WithCheckForOverflow(inst.CheckForOverflow);
 			var left = Translate(inst.Left);
@@ -1312,8 +1297,12 @@ namespace ICSharpCode.Decompiler.CSharp
 			    || !IsCompatibleWithSign(left.Type, inst.Sign) || !IsCompatibleWithSign(right.Type, inst.Sign))
 			{
 				// Left and right operands are incompatible, so convert them to a common type
-				StackType targetStackType = inst.UnderlyingResultType == StackType.I ? StackType.I8 : inst.UnderlyingResultType;
+				Sign sign = inst.Sign;
-				IType targetType = compilation.FindType(targetStackType.ToKnownTypeCode(inst.Sign));
+				if (sign == Sign.None) {
+					// If the sign doesn't matter, try to use the same sign as expected by the context
+					sign = context.TypeHint.GetSign();
+				}
+				IType targetType = FindArithmeticType(inst.UnderlyingResultType, sign);
 				left = left.ConvertTo(NullableType.IsNullable(left.Type) ? NullableType.Create(compilation, targetType) : targetType, this);
 				right = right.ConvertTo(NullableType.IsNullable(right.Type) ? NullableType.Create(compilation, targetType) : targetType, this);
 				rr = resolverWithOverflowCheck.ResolveBinaryOperator(op, left.ResolveResult, right.ResolveResult);
@@ -1327,6 +1316,28 @@ namespace ICSharpCode.Decompiler.CSharp
 			return resultExpr;
 		}
 
+		IType FindType(StackType stackType, Sign sign)
+		{
+			if (stackType == StackType.I && settings.NativeIntegers) {
+				return sign == Sign.Unsigned ? SpecialType.NUInt : SpecialType.NInt;
+			} else {
+				return compilation.FindType(stackType.ToKnownTypeCode(sign));
+			}
+		}
+
+		IType FindArithmeticType(StackType stackType, Sign sign)
+		{
+			if (stackType == StackType.I) {
+				if (settings.NativeIntegers) {
+					return sign == Sign.Unsigned ? SpecialType.NUInt : SpecialType.NInt;
+				} else {
+					// If native integers are not available, use 64-bit arithmetic instead
+					stackType = StackType.I8;
+				}
+			} 
+			return compilation.FindType(stackType.ToKnownTypeCode(sign));
+		}
+
 		/// <summary>
 		/// Handle oversized arguments needing truncation; and avoid IntPtr/pointers in arguments.
 		/// </summary>
@@ -1339,17 +1350,17 @@ namespace ICSharpCode.Decompiler.CSharp
 			if (argStackType.IsIntegerType() && argStackType.GetSize() < argUType.GetSize()) {
 				// If the argument is oversized (needs truncation to match stack size of its ILInstruction),
 				// perform the truncation now.
-				IType targetType = compilation.FindType(argStackType.ToKnownTypeCode(sign));
+				IType targetType = FindType(argStackType, sign);
 				argUType = targetType;
 				if (isLifted)
 					targetType = NullableType.Create(compilation, targetType);
 				arg = arg.ConvertTo(targetType, this);
 			}
-			if (argUType.GetStackType() == StackType.I) {
+			if (argUType.IsKnownType(KnownTypeCode.IntPtr) || argUType.IsKnownType(KnownTypeCode.UIntPtr)) {
 				// None of the operators we might want to apply are supported by IntPtr/UIntPtr.
 				// Also, pointer arithmetic has different semantics (works in number of elements, not bytes).
 				// So any inputs of size StackType.I must be converted to long/ulong.
-				IType targetType = compilation.FindType(StackType.I8.ToKnownTypeCode(sign));
+				IType targetType = FindArithmeticType(StackType.I, sign);
 				if (isLifted)
 					targetType = NullableType.Create(compilation, targetType);
 				arg = arg.ConvertTo(targetType, this);
@@ -1631,7 +1642,11 @@ namespace ICSharpCode.Decompiler.CSharp
 		
 		protected internal override TranslatedExpression VisitConv(Conv inst, TranslationContext context)
 		{
-			var arg = Translate(inst.Argument);
+			Sign hintSign = inst.InputSign;
+			if (hintSign == Sign.None) {
+				hintSign = context.TypeHint.GetSign();
+			}
+			var arg = Translate(inst.Argument, typeHint: FindArithmeticType(inst.InputType, hintSign));
 			IType inputType = NullableType.GetUnderlyingType(arg.Type);
 			StackType inputStackType = inst.InputType;
 			// Note: we're dealing with two conversions here:
@@ -2344,8 +2359,17 @@ namespace ICSharpCode.Decompiler.CSharp
 
 		protected internal override TranslatedExpression VisitBox(Box inst, TranslationContext context)
 		{
+			IType targetType = inst.Type;
+			var arg = Translate(inst.Argument, typeHint: targetType);
+			if (settings.NativeIntegers && !arg.Type.Equals(targetType)) {
+				if (targetType.IsKnownType(KnownTypeCode.IntPtr)) {
+					targetType = SpecialType.NInt;
+				} else if (targetType.IsKnownType(KnownTypeCode.UIntPtr)) {
+					targetType = SpecialType.NUInt;
+				}
+			}
+			arg = arg.ConvertTo(targetType, this);
 			var obj = compilation.FindType(KnownTypeCode.Object);
-			var arg = Translate(inst.Argument, typeHint: inst.Type).ConvertTo(inst.Type, this);
 			return new CastExpression(ConvertType(obj), arg.Expression)
 				.WithILInstruction(inst)
 				.WithRR(new ConversionResolveResult(obj, arg.ResolveResult, Conversion.BoxingConversion));

ICSharpCode.Decompiler/CSharp/Resolver/CSharpResolver.cs

@@ -774,6 +774,11 @@ namespace ICSharpCode.Decompiler.CSharp.Resolver
 							return HandleEnumComparison(op, rhsType, isNullable, lhs, rhs);
 						} else if (lhsType is PointerType && rhsType is PointerType) {
 							return BinaryOperatorResolveResult(compilation.FindType(KnownTypeCode.Boolean), lhs, op, rhs);
+						} else if (lhsType.IsCSharpNativeIntegerType() || rhsType.IsCSharpNativeIntegerType()) {
+							if (lhsType.Equals(rhsType))
+								return BinaryOperatorResolveResult(compilation.FindType(KnownTypeCode.Boolean), lhs, op, rhs, isLifted: isNullable);
+							else
+								return new ErrorResolveResult(compilation.FindType(KnownTypeCode.Boolean));
 						}
 						if (op == BinaryOperatorType.Equality || op == BinaryOperatorType.InEquality) {
 							if (lhsType.IsReferenceType == true && rhsType.IsReferenceType == true) {
@@ -855,6 +860,15 @@ namespace ICSharpCode.Decompiler.CSharp.Resolver
 				default:
 					throw new InvalidOperationException();
 			}
+			if (lhsType.IsCSharpNativeIntegerType() || rhsType.IsCSharpNativeIntegerType()) {
+				if (lhsType.Equals(rhsType)) {
+					return BinaryOperatorResolveResult(
+						isNullable ? NullableType.Create(compilation, lhsType) : lhsType,
+						lhs, op, rhs, isLifted: isNullable);
+				}
+				// mixing nint/nuint is not allowed
+				return new ErrorResolveResult(lhsType);
+			}
 			OverloadResolution builtinOperatorOR = CreateOverloadResolution(new[] { lhs, rhs });
 			foreach (var candidate in methodGroup) {
 				builtinOperatorOR.AddCandidate(candidate);
@@ -1000,8 +1014,22 @@ namespace ICSharpCode.Decompiler.CSharp.Resolver
 		bool BinaryNumericPromotion(bool isNullable, ref ResolveResult lhs, ref ResolveResult rhs, bool allowNullableConstants)
 		{
 			// C# 4.0 spec: §7.3.6.2
-			TypeCode lhsCode = ReflectionHelper.GetTypeCode(NullableType.GetUnderlyingType(lhs.Type));
+			var lhsUType = NullableType.GetUnderlyingType(lhs.Type);
-			TypeCode rhsCode = ReflectionHelper.GetTypeCode(NullableType.GetUnderlyingType(rhs.Type));
+			var rhsUType = NullableType.GetUnderlyingType(rhs.Type);
+			TypeCode lhsCode = ReflectionHelper.GetTypeCode(lhsUType);
+			TypeCode rhsCode = ReflectionHelper.GetTypeCode(rhsUType);
+			// Treat C# 9 native integers as falling between int and long.
+			// However they don't have a TypeCode, so we hack around that here:
+			if (lhsUType.Kind == TypeKind.NInt) {
+				lhsCode = TypeCode.Int32;
+			} else if (lhsUType.Kind == TypeKind.NUInt) {
+				lhsCode = TypeCode.UInt32;
+			}
+			if (rhsUType.Kind == TypeKind.NInt) {
+				rhsCode = TypeCode.Int32;
+			} else if (rhsUType.Kind == TypeKind.NUInt) {
+				rhsCode = TypeCode.UInt32;
+			}
 			// if one of the inputs is the null literal, promote that to the type of the other operand
 			if (isNullable && lhs.Type.Kind == TypeKind.Null && rhsCode >= TypeCode.Boolean && rhsCode <= TypeCode.Decimal) {
 				lhs = CastTo(rhsCode, isNullable, lhs, allowNullableConstants);
@@ -1026,10 +1054,19 @@ namespace ICSharpCode.Decompiler.CSharp.Resolver
 				} else if (lhsCode == TypeCode.UInt64 || rhsCode == TypeCode.UInt64) {
 					targetType = TypeCode.UInt64;
 					bindingError = IsSigned(lhsCode, lhs) || IsSigned(rhsCode, rhs);
-				} else if (lhsCode == TypeCode.Int64 || rhsCode == TypeCode.Int64) {
+				} else if (lhsUType.Kind == TypeKind.NUInt || rhsUType.Kind == TypeKind.NUInt) {
-					targetType = TypeCode.Int64;
+					bindingError = IsSigned(lhsCode, lhs) || IsSigned(rhsCode, rhs);
+					lhs = CastTo(SpecialType.NUInt, isNullable, lhs, allowNullableConstants);
+					rhs = CastTo(SpecialType.NUInt, isNullable, rhs, allowNullableConstants);
+					return !bindingError;
 				} else if (lhsCode == TypeCode.UInt32 || rhsCode == TypeCode.UInt32) {
 					targetType = (IsSigned(lhsCode, lhs) || IsSigned(rhsCode, rhs)) ? TypeCode.Int64 : TypeCode.UInt32;
+				} else if (lhsCode == TypeCode.Int64 || rhsCode == TypeCode.Int64) {
+					targetType = TypeCode.Int64;
+				} else if (lhsUType.Kind == TypeKind.NInt || rhsUType.Kind == TypeKind.NInt) {
+					lhs = CastTo(SpecialType.NInt, isNullable, lhs, allowNullableConstants);
+					rhs = CastTo(SpecialType.NInt, isNullable, rhs, allowNullableConstants);
+					return !bindingError;
 				} else {
 					targetType = TypeCode.Int32;
 				}
@@ -1066,14 +1103,18 @@ namespace ICSharpCode.Decompiler.CSharp.Resolver
 
 		ResolveResult CastTo(TypeCode targetType, bool isNullable, ResolveResult expression, bool allowNullableConstants)
 		{
-			IType elementType = compilation.FindType(targetType);
+			return CastTo(compilation.FindType(targetType), isNullable, expression, allowNullableConstants);
-			IType nullableType = MakeNullable(elementType, isNullable);
+		}
+
+		ResolveResult CastTo(IType targetType, bool isNullable, ResolveResult expression, bool allowNullableConstants)
+		{
+			IType nullableType = MakeNullable(targetType, isNullable);
 			if (nullableType.Equals(expression.Type))
 				return expression;
 			if (allowNullableConstants && expression.IsCompileTimeConstant) {
 				if (expression.ConstantValue == null)
 					return new ConstantResolveResult(nullableType, null);
-				ResolveResult rr = ResolveCast(elementType, expression);
+				ResolveResult rr = ResolveCast(targetType, expression);
 				if (rr.IsError)
 					return rr;
 				Debug.Assert(rr.IsCompileTimeConstant);
@@ -1262,7 +1303,8 @@ namespace ICSharpCode.Decompiler.CSharp.Resolver
 			// C# 4.0 spec: §7.7.6 Cast expressions
 			Conversion c = conversions.ExplicitConversion(expression, targetType);
 			if (expression.IsCompileTimeConstant && !c.IsUserDefined) {
-				TypeCode code = ReflectionHelper.GetTypeCode(targetType);
+				IType underlyingType = targetType.GetEnumUnderlyingType();
+				TypeCode code = ReflectionHelper.GetTypeCode(underlyingType);
 				if (code >= TypeCode.Boolean && code <= TypeCode.Decimal && expression.ConstantValue != null) {
 					try {
 						return new ConstantResolveResult(targetType, CSharpPrimitiveCast(code, expression.ConstantValue));
@@ -1276,19 +1318,18 @@ namespace ICSharpCode.Decompiler.CSharp.Resolver
 						return new ConstantResolveResult(targetType, expression.ConstantValue);
 					else
 						return new ErrorResolveResult(targetType);
-				} else if (targetType.Kind == TypeKind.Enum) {
+				} else if ((underlyingType.Kind == TypeKind.NInt || underlyingType.Kind == TypeKind.NUInt) && expression.ConstantValue != null) {
-					code = ReflectionHelper.GetTypeCode(GetEnumUnderlyingType(targetType));
+					code = (underlyingType.Kind == TypeKind.NInt ? TypeCode.Int32 : TypeCode.UInt32);
-					if (code >= TypeCode.SByte && code <= TypeCode.UInt64 && expression.ConstantValue != null) {
 					try {
-							return new ConstantResolveResult(targetType, CSharpPrimitiveCast(code, expression.ConstantValue));
+						return new ConstantResolveResult(targetType, Util.CSharpPrimitiveCast.Cast(code, expression.ConstantValue, checkForOverflow: true));
 					} catch (OverflowException) {
-							return new ErrorResolveResult(targetType);
+						// If constant value doesn't fit into 32-bits, the conversion is not a compile-time constant
+						return new ConversionResolveResult(targetType, expression, c, checkForOverflow);
 					} catch (InvalidCastException) {
 						return new ErrorResolveResult(targetType);
 					}
 				}
 			}
-			}
 			return new ConversionResolveResult(targetType, expression, c, checkForOverflow);
 		}
 		

ICSharpCode.Decompiler/CSharp/Syntax/TypeSystemAstBuilder.cs

@@ -722,7 +722,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 				return ace;
 			} else if (rr.IsCompileTimeConstant) {
 				var expr = ConvertConstantValue(rr.Type, rr.ConstantValue);
-				if (isBoxing && rr.Type.IsCSharpSmallIntegerType()) {
+				if (isBoxing && (rr.Type.IsCSharpSmallIntegerType() || rr.Type.IsCSharpNativeIntegerType())) {
 					// C# does not have small integer literal types.
 					// We need to add a cast so that the integer literal gets boxed as the correct type.
 					expr = new CastExpression(ConvertType(rr.Type), expr);
@@ -793,21 +793,24 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 				if (type.IsKnownType(KnownTypeCode.Double) || type.IsKnownType(KnownTypeCode.Single))
 					return ConvertFloatingPointLiteral(type, constantValue);
 				IType literalType = type;
-				bool smallInteger = type.IsCSharpSmallIntegerType();
+				bool integerTypeMismatch = type.IsCSharpSmallIntegerType() || type.IsCSharpNativeIntegerType();
-				if (smallInteger) { 
+				if (integerTypeMismatch) {
 					// C# does not have integer literals of small integer types,
 					// use `int` literal instead.
-					constantValue = CSharpPrimitiveCast.Cast(TypeCode.Int32, constantValue, false);
+					// It also doesn't have native integer literals, those also use `int` (or `uint` for `nuint`).
-					literalType = type.GetDefinition().Compilation.FindType(KnownTypeCode.Int32);
+					bool unsigned = type.Kind == TypeKind.NUInt;
+					constantValue = CSharpPrimitiveCast.Cast(unsigned ? TypeCode.UInt32 : TypeCode.Int32, constantValue, false);
+					var compilation = resolver?.Compilation ?? expectedType.GetDefinition()?.Compilation;
+					literalType = compilation?.FindType(unsigned ? KnownTypeCode.UInt32 : KnownTypeCode.Int32);
 				}
 				LiteralFormat format = LiteralFormat.None;
 				if (PrintIntegralValuesAsHex) {
 					format = LiteralFormat.HexadecimalNumber;
 				}
 				expr = new PrimitiveExpression(constantValue, format);
-				if (AddResolveResultAnnotations)
+				if (AddResolveResultAnnotations && literalType != null)
 					expr.AddAnnotation(new ConstantResolveResult(literalType, constantValue));
-				if (smallInteger && !type.Equals(expectedType)) {
+				if (integerTypeMismatch && !type.Equals(expectedType)) {
 					expr = new CastExpression(ConvertType(type), expr);
 				}
 				return expr;
@@ -822,7 +825,9 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 			// find IType of constant in compilation.
 			var constantType = expectedType;
 			if (!expectedType.IsKnownType(info.Type)) {
-				var compilation = expectedType.GetDefinition().Compilation;
+				var compilation = resolver?.Compilation ?? expectedType.GetDefinition()?.Compilation;
+				if (compilation == null)
+					return false;
 				constantType = compilation.FindType(info.Type);
 			}
 			// if the field definition cannot be found, do not generate a reference to the field.

ICSharpCode.Decompiler/IL/ILTypeExtensions.cs

@@ -202,7 +202,7 @@ namespace ICSharpCode.Decompiler.IL
 						case BinaryNumericOperator.BitXor:
 							var left = bni.Left.InferType(compilation);
 							var right = bni.Right.InferType(compilation);
-							if (left.Equals(right) && (left.IsCSharpPrimitiveIntegerType() || left.IsKnownType(KnownTypeCode.Boolean)))
+							if (left.Equals(right) && (left.IsCSharpPrimitiveIntegerType() || left.IsCSharpNativeIntegerType() || left.IsKnownType(KnownTypeCode.Boolean)))
 								return left;
 							else
 								return SpecialType.UnknownType;

ICSharpCode.Decompiler/TypeSystem/TypeUtils.cs

@@ -133,6 +133,22 @@ namespace ICSharpCode.Decompiler.TypeSystem
 			}
 		}
 
+		/// <summary>
+		/// Gets whether the type is a C# 9 native integer type: nint or nuint.
+		/// 
+		/// Returns false for (U)IntPtr.
+		/// </summary>
+		public static bool IsCSharpNativeIntegerType(this IType type)
+		{
+			switch (type.Kind) {
+				case TypeKind.NInt:
+				case TypeKind.NUInt:
+					return true;
+				default:
+					return false;
+			}
+		}
+
 		/// <summary>
 		/// Gets whether the type is a C# primitive integer type: byte, sbyte, short, ushort, int, uint, long and ulong.
 		///