Work for throw expressions.

ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs

@@ -746,6 +746,13 @@ namespace ICSharpCode.Decompiler.CSharp
 			return HandleThreeValuedLogic(inst, BinaryOperatorType.BitwiseOr, ExpressionType.Or);
 		}
 
+		protected internal override TranslatedExpression VisitThrow(Throw inst, TranslationContext context)
+		{
+			return new ThrowExpression(Translate(inst.Argument))
+				.WithILInstruction(inst)
+				.WithRR(new ResolveResult(SpecialType.NoType));
+		}
+
 		TranslatedExpression HandleThreeValuedLogic(BinaryInstruction inst, BinaryOperatorType op, ExpressionType eop)
 		{
 			var left = Translate(inst.Left);
@@ -2181,7 +2188,9 @@ namespace ICSharpCode.Decompiler.CSharp
 			var rr = resolver.ResolveBinaryOperator(BinaryOperatorType.NullCoalescing, value.ResolveResult, fallback.ResolveResult);
 			if (rr.IsError) {
 				IType targetType;
-				if (!value.Type.Equals(SpecialType.NullType) && !fallback.Type.Equals(SpecialType.NullType) && !value.Type.Equals(fallback.Type)) {
+				if (fallback.Expression is ThrowExpression && fallback.Type.Equals(SpecialType.NoType)) {
+					targetType = value.Type;
+				} else if (!value.Type.Equals(SpecialType.NullType) && !fallback.Type.Equals(SpecialType.NullType) && !value.Type.Equals(fallback.Type)) {
 					targetType = compilation.FindType(inst.UnderlyingResultType.ToKnownTypeCode());
 				} else {
 					targetType = value.Type.Equals(SpecialType.NullType) ? fallback.Type : value.Type;

ICSharpCode.Decompiler/CSharp/TranslatedExpression.cs

@@ -203,6 +203,9 @@ namespace ICSharpCode.Decompiler.CSharp
 			if (targetType.Kind == TypeKind.Unknown || targetType.Kind == TypeKind.Void || targetType.Kind == TypeKind.None) {
 				return this; // don't attempt to insert cast to '?' or 'void' as these are not valid.
 			}
+			if (Expression is ThrowExpression) {
+				return this; // Throw expressions have no type and are implicitly convertible to any type
+			}
 			if (Expression is TupleExpression tupleExpr && targetType is TupleType targetTupleType
 				&& tupleExpr.Elements.Count == targetTupleType.ElementTypes.Length)
 			{

ICSharpCode.Decompiler/IL/Instructions.cs

@@ -4225,7 +4225,7 @@ namespace ICSharpCode.Decompiler.IL
 		public Throw(ILInstruction argument) : base(OpCode.Throw, argument)
 		{
 		}
-		public override StackType ResultType { get { return StackType.Void; } }
+		public override StackType ResultType { get { return this.resultType; } }
 		protected override InstructionFlags ComputeFlags()
 		{
 			return base.ComputeFlags() | InstructionFlags.MayThrow | InstructionFlags.EndPointUnreachable;

ICSharpCode.Decompiler/IL/Instructions.tt

@@ -250,7 +250,7 @@
 		new OpCode("default.value", "Returns the default value for a type.",
 			NoArguments, HasTypeOperand, ResultType("type.GetStackType()")),
 		new OpCode("throw", "Throws an exception.",
-			Unary, MayThrow, UnconditionalBranch),
+			Unary, MayThrow, HasFlag("InstructionFlags.EndPointUnreachable"), ResultType("this.resultType")),
 		new OpCode("rethrow", "Rethrows the current exception.",
 			NoArguments, MayThrow, UnconditionalBranch),
 		new OpCode("sizeof", "Gets the size of a type in bytes.",

ICSharpCode.Decompiler/IL/Instructions/TryInstruction.cs

@@ -366,4 +366,9 @@ namespace ICSharpCode.Decompiler.IL
 			}
 		}
 	}
+
+	public partial class Throw
+	{
+		internal StackType resultType = StackType.Void;
+	}
 }

ICSharpCode.Decompiler/IL/Transforms/NullCoalescingTransform.cs

@@ -46,6 +46,15 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 		/// }
 		/// =>
 		/// stloc s(if.notnull(valueInst, fallbackInst))
+		/// 
+		/// -------------------
+		/// 
+		/// stloc obj(valueInst)
+		///	if (comp(ldloc obj == ldnull)) {
+		///		throw(...)
+		///	}
+		///	=>
+		///	stloc obj(if.notnull(valueInst, throw(...)))
 		/// </summary>
 		bool TransformRefTypes(Block block, int pos, StatementTransformContext context)
 		{
@@ -55,15 +64,69 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 				return false;
 			if (!block.Instructions[pos + 1].MatchIfInstruction(out var condition, out var trueInst))
 				return false;
+			if (!(condition.MatchCompEquals(out var left, out var right) && left.MatchLdLoc(stloc.Variable) && right.MatchLdNull()))
+				return false;
 			trueInst = Block.Unwrap(trueInst);
-			if (condition.MatchCompEquals(out var left, out var right) && left.MatchLdLoc(stloc.Variable) && right.MatchLdNull()
-				&& trueInst.MatchStLoc(stloc.Variable, out var fallbackValue)
-			) {
+			if (trueInst.MatchStLoc(stloc.Variable, out var fallbackValue)) {
 				context.Step("NullCoalescingTransform (reference types)", stloc);
 				stloc.Value = new NullCoalescingInstruction(NullCoalescingKind.Ref, stloc.Value, fallbackValue);
 				block.Instructions.RemoveAt(pos + 1); // remove if instruction
 				ILInlining.InlineOneIfPossible(block, pos, false, context);
 				return true;
+			} else if (trueInst is Throw throwInst) {
+				context.Step("NullCoalescingTransform (throw expression)", stloc);
+				throwInst.resultType = StackType.O;
+				stloc.Value = new NullCoalescingInstruction(NullCoalescingKind.Ref, stloc.Value, throwInst);
+				block.Instructions.RemoveAt(pos + 1); // remove if instruction
+				ILInlining.InlineOneIfPossible(block, pos, false, context);
+				return true;
+			}
+			return false;
+		}
+
+		/// <summary>
+		/// Handles NullCoalescingInstruction case 1: reference types.
+		/// 
+		/// stloc s(valueInst)
+		/// if (comp(ldloc s == ldnull)) {
+		///		stloc s(fallbackInst)
+		/// }
+		/// =>
+		/// stloc s(if.notnull(valueInst, fallbackInst))
+		/// 
+		/// -------------------
+		/// 
+		/// stloc obj(valueInst)
+		///	if (comp(ldloc obj == ldnull)) {
+		///		throw(...)
+		///	}
+		///	=>
+		///	stloc obj(if.notnull(valueInst, throw(...)))
+		/// </summary>
+		bool TransformRefTypesA(Block block, int pos, StatementTransformContext context)
+		{
+			if (!(block.Instructions[pos] is StLoc stloc))
+				return false;
+			if (stloc.Variable.Kind != VariableKind.StackSlot)
+				return false;
+			if (!block.Instructions[pos + 1].MatchIfInstruction(out var condition, out var trueInst))
+				return false;
+			if (!(condition.MatchCompEquals(out var left, out var right) && left.MatchLdLoc(stloc.Variable) && right.MatchLdNull()))
+				return false;
+			trueInst = Block.Unwrap(trueInst);
+			if (trueInst.MatchStLoc(stloc.Variable, out var fallbackValue)) {
+				context.Step("NullCoalescingTransform (reference types)", stloc);
+				stloc.Value = new NullCoalescingInstruction(NullCoalescingKind.Ref, stloc.Value, fallbackValue);
+				block.Instructions.RemoveAt(pos + 1); // remove if instruction
+				ILInlining.InlineOneIfPossible(block, pos, false, context);
+				return true;
+			} else if (trueInst is Throw throwInst) {
+				context.Step("NullCoalescingTransform (throw expression)", stloc);
+				throwInst.resultType = StackType.O;
+				stloc.Value = new NullCoalescingInstruction(NullCoalescingKind.Ref, stloc.Value, throwInst);
+				block.Instructions.RemoveAt(pos + 1); // remove if instruction
+				ILInlining.InlineOneIfPossible(block, pos, false, context);
+				return true;
 			}
 			return false;
 		}