#nullable enable for Instructions.tt

ICSharpCode.Decompiler/IL/Instructions.tt

@@ -16,6 +16,8 @@
 // OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 // DEALINGS IN THE SOFTWARE.
 
+#nullable enable
+
 <#@ template debug="false" hostspecific="false" language="C#" #>
 <#@ assembly name="System.Core" #>
 <#@ import namespace="System.Linq" #>
@@ -32,7 +34,7 @@
 			AbstractBaseClass, CustomArguments(("left", null), ("right", null)), HasFlag("InstructionFlags.None")),
 		new OpCode("CallInstruction", "Instruction with a list of arguments.",
 			AbstractBaseClass, CustomChildren(new []{ new ArgumentInfo("arguments") { IsCollection = true }}),
-			CustomWriteTo, MayThrow, SideEffect),
+			CustomConstructor, CustomWriteTo, MayThrow, SideEffect),
 		new OpCode("PatternInstruction", "Base class for pattern matching in ILAst.", AbstractBaseClass, ResultType("Unknown")) { Namespace = "ICSharpCode.Decompiler.IL.Patterns" },
 		new OpCode("CompoundAssignmentInstruction", "Common instruction for compound assignments.",
 			AbstractBaseClass, CustomConstructor, CustomArguments(("target", null), ("value", null))),
@@ -68,7 +70,7 @@
 				new ChildInfo("init") { CanInlineInto = true },
 				new ChildInfo("body")
 			}),
-			CustomInvariant("Debug.Assert(Variable.Kind == VariableKind.PinnedRegionLocal);")),
+			CustomInvariant("DebugAssert(Variable.Kind == VariableKind.PinnedRegionLocal);")),
 		new OpCode("binary", "Common instruction for add, sub, mul, div, rem, bit.and, bit.or, bit.xor, shl and shr.",
 			CustomClassName("BinaryNumericInstruction"), Binary, CustomWriteTo, CustomConstructor, CustomComputeFlags,
 			MatchCondition("CheckForOverflow == o.CheckForOverflow && Sign == o.Sign && Operator == o.Operator && IsLifted == o.IsLifted")),
@@ -215,11 +217,11 @@
 		new OpCode("ldnull", "Loads the null reference.",
 			CustomClassName("LdNull"), NoArguments, ResultType("O")),
 		new OpCode("ldftn", "Load method pointer",
-			CustomClassName("LdFtn"), NoArguments, HasMethodOperand, ResultType("I")),
+			CustomClassName("LdFtn"), NoArguments, HasMethodOperand(), ResultType("I")),
 		new OpCode("ldvirtftn", "Load method pointer",
-			CustomClassName("LdVirtFtn"), Unary, HasMethodOperand, MayThrow, ResultType("I")),
+			CustomClassName("LdVirtFtn"), Unary, HasMethodOperand(), MayThrow, ResultType("I")),
 		new OpCode("ldvirtdelegate", "Virtual delegate construction",
-			CustomClassName("LdVirtDelegate"), Unary, HasTypeOperand, HasMethodOperand,
+			CustomClassName("LdVirtDelegate"), Unary, HasTypeOperand, HasMethodOperand(),
 			MayThrow, ResultType("O")),
 		new OpCode("ldtypetoken", "Loads runtime representation of metadata token",
 			CustomClassName("LdTypeToken"), NoArguments, HasTypeOperand, ResultType("O")),
@@ -287,7 +289,7 @@
 				+ "The input must be an object reference (O)." + Environment.NewLine
 				+ "If the input is an array/string, evaluates to a reference to the first element/character, or to a null reference if the array is null or empty." + Environment.NewLine
 				+ "Otherwise, uses the GetPinnableReference method to get the reference, or evaluates to a null reference if the input is null." + Environment.NewLine,
-			CustomArguments(("argument", new[] { "O" })), ResultType("Ref"), HasMethodOperand),
+			CustomArguments(("argument", new[] { "O" })), ResultType("Ref"), HasMethodOperand(nullable: true)),
 		new OpCode("string.to.int", "Maps a string value to an integer. This is used in switch(string).",
 			CustomArguments(("argument", new[] { "O" })), CustomConstructor, CustomWriteTo, ResultType("I4")),
 
@@ -297,7 +299,7 @@
 
 		new OpCode("user.logic.operator", "Use of user-defined &amp;&amp; or || operator.",
 			CustomClassName("UserDefinedLogicOperator"),
-			HasMethodOperand, ResultType("O"),
+			HasMethodOperand(), ResultType("O"),
 			CustomChildren(new []{
 				new ChildInfo("left") { CanInlineInto = true },
 				new ChildInfo("right") { CanInlineInto = false } // only executed depending on value of left
@@ -337,7 +339,7 @@
 			CustomClassName("DynamicIsEventInstruction"), Dynamic, CustomArguments(("argument", new[] { "O" })), CustomWriteTo),
 
 		new OpCode("match", "ILAst representation of C# patterns",
-			CustomClassName("MatchInstruction"), HasVariableOperand("Store"), HasMethodOperand,
+			CustomClassName("MatchInstruction"), HasVariableOperand("Store"), HasMethodOperand(nullable: true),
 			BoolFlag("IsDeconstructCall"), BoolFlag("IsDeconstructTuple"), BoolFlag("CheckType"), BoolFlag("CheckNotNull"),
 			CustomChildren(new []{
 				new ChildInfo("testedOperand") { CanInlineInto = true },
@@ -371,8 +373,8 @@
 	};
 #>
 using System;
-using System.Collections.Generic;
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using ICSharpCode.Decompiler.TypeSystem;
 
@@ -437,7 +439,7 @@ namespace <#=opCode.Namespace#>
 		}
 <#	} #>
 <#		if (opCode.GeneratePerformMatch) { #>
-		protected internal override bool PerformMatch(ILInstruction other, ref Patterns.Match match)
+		protected internal override bool PerformMatch(ILInstruction? other, ref Patterns.Match match)
 		{
 			var o = other as <#=opCode.Name#>;
 			return <#=string.Join(" && ", opCode.PerformMatchConditions)#>;
@@ -637,10 +639,15 @@ namespace ICSharpCode.Decompiler.IL
 		public string TypeName;
 		public string Name;
 		public string FieldName;
+		public bool IsReferenceType = true;
 		
 		public override string ToString()
 		{
-			return "out " + TypeName + " " + Name;
+			if (IsReferenceType) {
+				return "[NotNullWhen(true)] out " + TypeName + "? " + Name;
+			} else {
+				return "out " + TypeName + " " + Name;
+			}
 		}
 	}
 	
@@ -866,7 +873,7 @@ namespace ICSharpCode.Decompiler.IL
 						opCode.WriteArguments.Add("output.Write(\", \");");
 					opCode.WriteArguments.Add("this." + arg + ".WriteTo(output, options);");
 					opCode.Members.Add("public static readonly SlotInfo " + children[i].SlotName + " = " + children[i].GetSlotInit() + ";");
-					opCode.Members.Add("ILInstruction " + arg + ";");
+					opCode.Members.Add("ILInstruction " + arg + " = null!;");
 					opCode.Members.Add("public ILInstruction " + argProp + " {" + Environment.NewLine
 						+ "\tget { return this." + arg + "; }" + Environment.NewLine
 						+ "\tset {" + Environment.NewLine
@@ -885,7 +892,7 @@ namespace ICSharpCode.Decompiler.IL
 							checkString += " || ";
 						checkString += arg + ".ResultType == " + expectedTypeCode;
 					}
-					opCode.Invariants.Add("Debug.Assert(" + checkString + ");");
+					opCode.Invariants.Add("DebugAssert(" + checkString + ");");
 				}
 			}
 			opCode.WriteArguments.Add("output.Write(')');");
@@ -1008,8 +1015,7 @@ namespace ICSharpCode.Decompiler.IL
 		Action<OpCode> action = opCode => {
 			opCode.ConstructorParameters.Add("ILVariable variable");
 			opCode.Members.Add("ILVariable variable;");
-			opCode.ConstructorBody.Add("Debug.Assert(variable != null);");
-			opCode.ConstructorBody.Add("this.variable = variable;");
+			opCode.ConstructorBody.Add("this.variable = variable ?? throw new ArgumentNullException(nameof(variable));");
 			opCode.MatchParameters.Add(new MatchParamInfo { TypeName = "ILVariable", Name = "variable", FieldName = "Variable" });
 			opCode.PerformMatchConditions.Add("variable == o.variable");
 			opCode.GenerateWriteTo = true;
@@ -1019,7 +1025,7 @@ namespace ICSharpCode.Decompiler.IL
 			opCode.Members.Add(@"public ILVariable Variable {
 	get { return variable; }
 	set {
-		Debug.Assert(value != null);
+		DebugAssert(value != null);
 		if (IsConnected)
 			variable.RemoveAccessInstruction(this);
 		variable = value;
@@ -1048,8 +1054,8 @@ protected override void Disconnected()
 }
 ".Replace("Access", accessType));
 			if (generateCheckInvariant) {
-				opCode.Invariants.Add("Debug.Assert(phase <= ILPhase.InILReader || this.IsDescendantOf(variable.Function));");
-				opCode.Invariants.Add("Debug.Assert(phase <= ILPhase.InILReader || variable.Function.Variables[variable.IndexInFunction] == variable);");
+				opCode.Invariants.Add("DebugAssert(phase <= ILPhase.InILReader || this.IsDescendantOf(variable.Function!));");
+				opCode.Invariants.Add("DebugAssert(phase <= ILPhase.InILReader || variable.Function!.Variables[variable.IndexInFunction] == variable);");
 			}
 		};
 		if (accessType == "Load") {
@@ -1093,22 +1099,26 @@ protected override void Disconnected()
 		opCode.WriteOperand.Add("type.WriteTo(output);");
 	};
 
-	static Action<OpCode> HasMethodOperand = opCode => {
-		opCode.ConstructorParameters.Add("IMethod method");
-		opCode.Members.Add("readonly IMethod method;");
-		opCode.ConstructorBody.Add("this.method = method;");
-		opCode.MatchParameters.Add(new MatchParamInfo { TypeName = "IMethod", Name = "method", FieldName = "Method" });
-		opCode.PerformMatchConditions.Add("object.Equals(method, o.method)");
-		opCode.Members.Add("/// <summary>Returns the method operand.</summary>" + Environment.NewLine
-						+ "public IMethod Method { get { return method; } }");
-		opCode.GenerateWriteTo = true;
-		opCode.WriteOperand.Add("if (method != null) {");
-		opCode.WriteOperand.Add("\toutput.Write(' ');");
-		opCode.WriteOperand.Add("\tmethod.WriteTo(output);");
-		opCode.WriteOperand.Add("}");
-		opCode.Interfaces.Add("IInstructionWithMethodOperand");
-	};
-	
+	static Action<OpCode> HasMethodOperand(bool nullable = false)
+	{
+		return opCode => {
+			string n = nullable ? "?" : "";
+			opCode.ConstructorParameters.Add($"IMethod{n} method");
+			opCode.Members.Add($"readonly IMethod{n} method;");
+			opCode.ConstructorBody.Add("this.method = method;");
+			opCode.MatchParameters.Add(new MatchParamInfo { TypeName = $"IMethod{n}", Name = "method", FieldName = "Method", IsReferenceType = !nullable });
+			opCode.PerformMatchConditions.Add("object.Equals(method, o.method)");
+			opCode.Members.Add("/// <summary>Returns the method operand.</summary>" + Environment.NewLine
+							+ $"public IMethod{n} Method => method;");
+			opCode.GenerateWriteTo = true;
+			opCode.WriteOperand.Add("if (method != null) {");
+			opCode.WriteOperand.Add("\toutput.Write(' ');");
+			opCode.WriteOperand.Add("\tmethod.WriteTo(output);");
+			opCode.WriteOperand.Add("}");
+			opCode.Interfaces.Add("IInstructionWithMethodOperand");
+		};
+	}
+
 	static Action<OpCode> HasMemberOperand = opCode => {
 		opCode.ConstructorParameters.Add("IMember member");
 		opCode.Members.Add("readonly IMember member;");
@@ -1139,7 +1149,12 @@ protected override void Disconnected()
 		return opCode => {
 			NoArguments(opCode);
 			opCode.ConstructorParameters.Add(operandType + " value");
-			opCode.MatchParameters.Add(new MatchParamInfo { TypeName = operandType, Name = "value", FieldName = "Value" });
+			opCode.MatchParameters.Add(new MatchParamInfo {
+				TypeName = operandType,
+				Name = "value",
+				FieldName = "Value",
+				IsReferenceType = operandType == "string"
+			});
 			opCode.PerformMatchConditions.Add("this.Value == o.Value");
 			opCode.Members.Add("public readonly " + operandType + " Value;");
 			opCode.ConstructorBody.Add("this.Value = value;");

ICSharpCode.Decompiler/IL/Instructions/Block.cs

@@ -124,10 +124,10 @@ namespace ICSharpCode.Decompiler.IL
 					foreach (var inst in Instructions)
 					{
 						var stloc = inst as StLoc;
-						Debug.Assert(stloc != null, "Instructions in CallWithNamedArgs must be assignments");
-						Debug.Assert(stloc!.Variable.Kind == VariableKind.NamedArgument);
-						Debug.Assert(stloc.Variable.IsSingleDefinition && stloc.Variable.LoadCount == 1);
-						Debug.Assert(stloc.Variable.LoadInstructions.Single().Parent == finalInstruction);
+						DebugAssert(stloc != null, "Instructions in CallWithNamedArgs must be assignments");
+						DebugAssert(stloc.Variable.Kind == VariableKind.NamedArgument);
+						DebugAssert(stloc.Variable.IsSingleDefinition && stloc.Variable.LoadCount == 1);
+						DebugAssert(stloc.Variable.LoadInstructions.Single().Parent == finalInstruction);
 					}
 					var call = (CallInstruction)finalInstruction;
 					if (call.IsInstanceCall)
@@ -144,9 +144,9 @@ namespace ICSharpCode.Decompiler.IL
 					Debug.Assert(Instructions[0].MatchStLoc(final!.Variable, out var init) && init.MatchNewArr(out type));
 					for (int i = 1; i < Instructions.Count; i++)
 					{
-						Debug.Assert(Instructions[i].MatchStObj(out ILInstruction? target, out _, out var t) && type != null && type.Equals(t));
-						Debug.Assert(target.MatchLdElema(out t, out ILInstruction? array) && type!.Equals(t));
-						Debug.Assert(array.MatchLdLoc(out ILVariable? v) && v == final.Variable);
+						DebugAssert(Instructions[i].MatchStObj(out ILInstruction? target, out _, out var t) && type != null && type.Equals(t));
+						DebugAssert(target.MatchLdElema(out t, out ILInstruction? array) && type.Equals(t));
+						DebugAssert(array.MatchLdLoc(out ILVariable? v) && v == final.Variable);
 					}
 					break;
 				case BlockKind.CollectionInitializer:

ICSharpCode.Decompiler/IL/Instructions/DeconstructResultInstruction.cs

@@ -61,10 +61,10 @@ namespace ICSharpCode.Decompiler.IL
 		void AdditionalInvariants()
 		{
 			var matchInst = FindMatch();
-			Debug.Assert(matchInst != null && (matchInst.IsDeconstructCall || matchInst.IsDeconstructTuple));
-			Debug.Assert(Argument.MatchLdLoc(matchInst!.Variable));
+			DebugAssert(matchInst != null && (matchInst.IsDeconstructCall || matchInst.IsDeconstructTuple));
+			DebugAssert(Argument.MatchLdLoc(matchInst.Variable));
 			var outParamType = matchInst.GetDeconstructResultType(this.Index);
-			Debug.Assert(outParamType.GetStackType() == ResultType);
+			DebugAssert(outParamType.GetStackType() == ResultType);
 		}
 	}
 }

ICSharpCode.Decompiler/IL/Instructions/DynamicInstructions.cs

@@ -145,7 +145,7 @@ namespace ICSharpCode.Decompiler.IL
 		public DynamicConvertInstruction(CSharpBinderFlags binderFlags, IType type, IType? context, ILInstruction argument)
 			: base(OpCode.DynamicConvertInstruction, binderFlags, context)
 		{
-			Type = type;
+			this.type = type;
 			Argument = argument;
 		}
 

ICSharpCode.Decompiler/IL/Instructions/ExpressionTreeCast.cs

@@ -1,8 +1,4 @@
 #nullable enable
-using System;
-using System.Collections.Generic;
-using System.Text;
-
 using ICSharpCode.Decompiler.TypeSystem;
 
 namespace ICSharpCode.Decompiler.IL
@@ -14,7 +10,7 @@ namespace ICSharpCode.Decompiler.IL
 		public ExpressionTreeCast(IType type, ILInstruction argument, bool isChecked)
 			: base(OpCode.ExpressionTreeCast, argument)
 		{
-			this.Type = type;
+			this.type = type;
 			this.IsChecked = isChecked;
 		}
 

ICSharpCode.Decompiler/IL/Instructions/ILInstruction.cs

@@ -21,6 +21,7 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using System.Threading;
 
 using ICSharpCode.Decompiler.IL.Patterns;
@@ -70,6 +71,16 @@ namespace ICSharpCode.Decompiler.IL
 			// make sure to read the remarks on the ReplaceWith() method.
 		}
 
+		internal static void DebugAssert([DoesNotReturnIf(false)] bool b)
+		{
+			Debug.Assert(b);
+		}
+
+		internal static void DebugAssert([DoesNotReturnIf(false)] bool b, string msg)
+		{
+			Debug.Assert(b, msg);
+		}
+
 		[Conditional("DEBUG")]
 		internal virtual void CheckInvariant(ILPhase phase)
 		{
@@ -494,7 +505,7 @@ namespace ICSharpCode.Decompiler.IL
 
 			internal ChildrenEnumerator(ILInstruction inst)
 			{
-				Debug.Assert(inst != null);
+				DebugAssert(inst != null);
 				this.inst = inst;
 				this.pos = -1;
 				this.end = inst!.GetChildCount();
@@ -951,7 +962,7 @@ namespace ICSharpCode.Decompiler.IL
 
 	public interface IInstructionWithMethodOperand
 	{
-		IMethod Method { get; }
+		IMethod? Method { get; }
 	}
 
 	public interface ILiftableInstruction

ICSharpCode.Decompiler/IL/Instructions/MatchInstruction.cs

@@ -96,7 +96,7 @@ namespace ICSharpCode.Decompiler.IL
 		public int NumPositionalPatterns {
 			get {
 				if (IsDeconstructCall)
-					return method.Parameters.Count - (method.IsStatic ? 1 : 0);
+					return method!.Parameters.Count - (method.IsStatic ? 1 : 0);
 				else if (IsDeconstructTuple)
 					return TupleType.GetTupleElementTypes(variable.Type).Length;
 				else
@@ -104,7 +104,7 @@ namespace ICSharpCode.Decompiler.IL
 			}
 		}
 
-		public MatchInstruction(ILVariable variable, ILInstruction? testedOperand)
+		public MatchInstruction(ILVariable variable, ILInstruction testedOperand)
 			: this(variable, method: null, testedOperand)
 		{
 		}
@@ -153,9 +153,9 @@ namespace ICSharpCode.Decompiler.IL
 		{
 			if (this.IsDeconstructCall)
 			{
-				int firstOutParam = (method.IsStatic ? 1 : 0);
-				var outParamType = this.Method.Parameters[firstOutParam + index].Type;
-				if (!(outParamType is ByReferenceType brt))
+				int firstOutParam = (method!.IsStatic ? 1 : 0);
+				var outParamType = method.Parameters[firstOutParam + index].Type;
+				if (outParamType is not ByReferenceType brt)
 					throw new InvalidOperationException("deconstruct out param must be by reference");
 				return brt.ElementType;
 			}
@@ -210,8 +210,11 @@ namespace ICSharpCode.Decompiler.IL
 			}
 		}
 
-		internal static bool IsDeconstructMethod(IMethod method)
+		internal static bool IsDeconstructMethod(IMethod? method)
 		{
+			if (method == null
+				)
+				return false;
 			if (method.Name != "Deconstruct")
 				return false;
 			if (method.ReturnType.Kind != TypeKind.Void)
@@ -260,7 +263,10 @@ namespace ICSharpCode.Decompiler.IL
 			if (IsDeconstructCall)
 			{
 				output.Write(".deconstruct[");
-				method.WriteTo(output);
+				if (method == null)
+					output.Write("<null>");
+				else
+					method.WriteTo(output);
 				output.Write(']');
 			}
 			if (IsDeconstructTuple)

ICSharpCode.Decompiler/IL/Instructions/StringToInt.cs

@@ -26,14 +26,14 @@ namespace ICSharpCode.Decompiler.IL
 	{
 		public List<(string? Key, int Value)> Map { get; }
 
-		public StringToInt(ILInstruction? argument, List<(string? Key, int Value)> map)
+		public StringToInt(ILInstruction argument, List<(string? Key, int Value)> map)
 			: base(OpCode.StringToInt)
 		{
 			this.Argument = argument;
 			this.Map = map;
 		}
 
-		public StringToInt(ILInstruction? argument, string?[] map)
+		public StringToInt(ILInstruction argument, string?[] map)
 			: this(argument, ArrayToDictionary(map))
 		{
 		}

ICSharpCode.Decompiler/Util/NullAttributes.cs

@@ -25,5 +25,13 @@ namespace System.Diagnostics.CodeAnalysis
 
 		public bool ReturnValue { get; }
 	}
+
+	[AttributeUsage(AttributeTargets.Parameter, Inherited = false)]
+	internal sealed class DoesNotReturnIfAttribute : Attribute
+	{
+		public DoesNotReturnIfAttribute(bool parameterValue) => ParameterValue = parameterValue;
+
+		public bool ParameterValue { get; }
+	}
 }
 #endif