Add support for calling `operator checked`.

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

@@ -217,6 +217,18 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 			c = a - b;
 			c = a * b;
 			c = a / b;
+#if CS110
+			checked
+			{
+				c = a + b;
+				c = a - b;
+				c = a * b;
+				c = a / b;
+			}
+			// force end of checked block:
+			++a;
+#endif
+
 			c = a % b;
 			c = a & b;
 			c = a | b;
@@ -232,6 +244,16 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 			c = +a;
 			c = ++a;
 			c = --a;
+#if CS110
+			checked
+			{
+				c = -a;
+				c = ++a;
+				c = --a;
+			}
+			// force end of checked block:
+			++a;
+#endif
 			if (a)
 			{
 				Console.WriteLine("a");
@@ -265,6 +287,11 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 				Console.WriteLine("a >= b");
 			}
 			int num = (int)a;
+#if CS110
+			num = checked((int)a);
+			// force end of checked block:
+			num = (int)a;
+#endif
 			a = num;
 		}
 	}

ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs

@@ -1810,6 +1810,15 @@ namespace ICSharpCode.Decompiler.CSharp
 			{
 				target = Translate(inst.Target, loadType);
 			}
+			var opType = OperatorDeclaration.GetOperatorType(inst.Method.Name);
+			if (opType != null && OperatorDeclaration.IsChecked(opType.Value))
+			{
+				target.Expression.AddAnnotation(AddCheckedBlocks.CheckedAnnotation);
+			}
+			else if (ReplaceMethodCallsWithOperators.HasCheckedEquivalent(inst.Method))
+			{
+				target.Expression.AddAnnotation(AddCheckedBlocks.UncheckedAnnotation);
+			}
 			if (UserDefinedCompoundAssign.IsStringConcat(inst.Method))
 			{
 				Debug.Assert(inst.Method.Parameters.Count == 2);
@@ -1876,8 +1885,10 @@ namespace ICSharpCode.Decompiler.CSharp
 			switch (name)
 			{
 				case "op_Increment":
+				case "op_CheckedIncrement":
 					return isPostfix ? UnaryOperatorType.PostIncrement : UnaryOperatorType.Increment;
 				case "op_Decrement":
+				case "op_CheckedDecrement":
 					return isPostfix ? UnaryOperatorType.PostDecrement : UnaryOperatorType.Decrement;
 				default:
 					return null;

ICSharpCode.Decompiler/CSharp/OutputVisitor/CSharpAmbience.cs

@@ -297,10 +297,16 @@ namespace ICSharpCode.Decompiler.CSharp.OutputVisitor
 							ConvertType(member.ReturnType, writer, formattingPolicy);
 							break;
 						case "op_Explicit":
+						case "op_CheckedExplicit":
 							writer.WriteKeyword(OperatorDeclaration.ExplicitRole, "explicit");
 							writer.Space();
 							writer.WriteKeyword(OperatorDeclaration.OperatorKeywordRole, "operator");
 							writer.Space();
+							if (member.Name == "op_CheckedExplicit")
+							{
+								writer.WriteToken(OperatorDeclaration.CheckedKeywordRole, "checked");
+								writer.Space();
+							}
 							ConvertType(member.ReturnType, writer, formattingPolicy);
 							break;
 						default:

ICSharpCode.Decompiler/CSharp/Transforms/ReplaceMethodCallsWithOperators.cs

@@ -16,6 +16,7 @@
 // OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 // DEALINGS IN THE SOFTWARE.
 
+using System;
 using System.Linq;
 using System.Reflection;
 
@@ -142,10 +143,19 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 					break;
 			}
 
-			BinaryOperatorType? bop = GetBinaryOperatorTypeFromMetadataName(method.Name, context.Settings);
+			bool isChecked;
+			BinaryOperatorType? bop = GetBinaryOperatorTypeFromMetadataName(method.Name, out isChecked, context.Settings);
 			if (bop != null && arguments.Length == 2)
 			{
 				invocationExpression.Arguments.Clear(); // detach arguments from invocationExpression
+				if (isChecked)
+				{
+					invocationExpression.AddAnnotation(AddCheckedBlocks.CheckedAnnotation);
+				}
+				else if (HasCheckedEquivalent(method))
+				{
+					invocationExpression.AddAnnotation(AddCheckedBlocks.UncheckedAnnotation);
+				}
 				invocationExpression.ReplaceWith(
 					new BinaryOperatorExpression(
 						arguments[0].UnwrapInDirectionExpression(),
@@ -155,9 +165,17 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 				);
 				return;
 			}
-			UnaryOperatorType? uop = GetUnaryOperatorTypeFromMetadataName(method.Name);
+			UnaryOperatorType? uop = GetUnaryOperatorTypeFromMetadataName(method.Name, out isChecked, context.Settings);
 			if (uop != null && arguments.Length == 1)
 			{
+				if (isChecked)
+				{
+					invocationExpression.AddAnnotation(AddCheckedBlocks.CheckedAnnotation);
+				}
+				else if (HasCheckedEquivalent(method))
+				{
+					invocationExpression.AddAnnotation(AddCheckedBlocks.UncheckedAnnotation);
+				}
 				if (uop == UnaryOperatorType.Increment || uop == UnaryOperatorType.Decrement)
 				{
 					// `op_Increment(a)` is not equivalent to `++a`,
@@ -174,17 +192,27 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 							).CopyAnnotationsFrom(invocationExpression)
 						);
 					}
-					return;
 				}
+				else
+				{
 					arguments[0].Remove(); // detach argument
 					invocationExpression.ReplaceWith(
 						new UnaryOperatorExpression(uop.Value, arguments[0].UnwrapInDirectionExpression()).CopyAnnotationsFrom(invocationExpression)
 					);
+				}
 				return;
 			}
-			if (method.Name == "op_Explicit" && arguments.Length == 1)
+			if (method.Name is "op_Explicit" or "op_CheckedExplicit" && arguments.Length == 1)
 			{
 				arguments[0].Remove(); // detach argument
+				if (method.Name == "op_CheckedExplicit")
+				{
+					invocationExpression.AddAnnotation(AddCheckedBlocks.CheckedAnnotation);
+				}
+				else if (HasCheckedEquivalent(method))
+				{
+					invocationExpression.AddAnnotation(AddCheckedBlocks.UncheckedAnnotation);
+				}
 				invocationExpression.ReplaceWith(
 					new CastExpression(context.TypeSystemAstBuilder.ConvertType(method.ReturnType), arguments[0].UnwrapInDirectionExpression())
 						.CopyAnnotationsFrom(invocationExpression)
@@ -200,6 +228,14 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 			return;
 		}
 
+		internal static bool HasCheckedEquivalent(IMethod method)
+		{
+			string name = method.Name;
+			if (name.StartsWith("op_", StringComparison.Ordinal))
+				name = "op_Checked" + name.Substring(3);
+			return method.DeclaringType.GetMethods(m => m.IsOperator && m.Name == name).Any();
+		}
+
 		bool IsInstantiableTypeParameter(IType type)
 		{
 			return type is ITypeParameter tp && tp.HasDefaultConstructorConstraint;
@@ -350,8 +386,9 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 			}
 		}
 
-		static BinaryOperatorType? GetBinaryOperatorTypeFromMetadataName(string name, DecompilerSettings settings)
+		static BinaryOperatorType? GetBinaryOperatorTypeFromMetadataName(string name, out bool isChecked, DecompilerSettings settings)
 		{
+			isChecked = false;
 			switch (name)
 			{
 				case "op_Addition":
@@ -362,6 +399,18 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 					return BinaryOperatorType.Multiply;
 				case "op_Division":
 					return BinaryOperatorType.Divide;
+				case "op_CheckedAddition" when settings.CheckedOperators:
+					isChecked = true;
+					return BinaryOperatorType.Add;
+				case "op_CheckedSubtraction" when settings.CheckedOperators:
+					isChecked = true;
+					return BinaryOperatorType.Subtract;
+				case "op_CheckedMultiply" when settings.CheckedOperators:
+					isChecked = true;
+					return BinaryOperatorType.Multiply;
+				case "op_CheckedDivision" when settings.CheckedOperators:
+					isChecked = true;
+					return BinaryOperatorType.Divide;
 				case "op_Modulus":
 					return BinaryOperatorType.Modulus;
 				case "op_BitwiseAnd":
@@ -393,8 +442,9 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 			}
 		}
 
-		static UnaryOperatorType? GetUnaryOperatorTypeFromMetadataName(string name)
+		static UnaryOperatorType? GetUnaryOperatorTypeFromMetadataName(string name, out bool isChecked, DecompilerSettings settings)
 		{
+			isChecked = false;
 			switch (name)
 			{
 				case "op_LogicalNot":
@@ -403,12 +453,21 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 					return UnaryOperatorType.BitNot;
 				case "op_UnaryNegation":
 					return UnaryOperatorType.Minus;
+				case "op_CheckedUnaryNegation" when settings.CheckedOperators:
+					isChecked = true;
+					return UnaryOperatorType.Minus;
 				case "op_UnaryPlus":
 					return UnaryOperatorType.Plus;
 				case "op_Increment":
 					return UnaryOperatorType.Increment;
 				case "op_Decrement":
 					return UnaryOperatorType.Decrement;
+				case "op_CheckedIncrement" when settings.CheckedOperators:
+					isChecked = true;
+					return UnaryOperatorType.Increment;
+				case "op_CheckedDecrement" when settings.CheckedOperators:
+					isChecked = true;
+					return UnaryOperatorType.Decrement;
 				default:
 					return null;
 			}

ICSharpCode.Decompiler/IL/Instructions/CompoundAssignmentInstruction.cs

@@ -315,7 +315,18 @@ namespace ICSharpCode.Decompiler.IL
 		{
 			this.Method = method;
 			Debug.Assert(Method.IsOperator || IsStringConcat(method));
-			Debug.Assert(evalMode == CompoundEvalMode.EvaluatesToNewValue || (Method.Name == "op_Increment" || Method.Name == "op_Decrement"));
+			Debug.Assert(evalMode == CompoundEvalMode.EvaluatesToNewValue || IsIncrementOrDecrement(method));
+		}
+
+		public static bool IsIncrementOrDecrement(IMethod method, DecompilerSettings? settings = null)
+		{
+			if (!(method.IsOperator && method.IsStatic))
+				return false;
+			if (method.Name is "op_Increment" or "op_Decrement")
+				return true;
+			if (method.Name is "op_CheckedIncrement" or "op_CheckedDecrement")
+				return settings?.CheckedOperators ?? true;
+			return false;
 		}
 
 		public static bool IsStringConcat(IMethod method)

ICSharpCode.Decompiler/IL/Transforms/FixRemainingIncrements.cs

@@ -31,7 +31,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			var callsToFix = new List<Call>();
 			foreach (var call in function.Descendants.OfType<Call>())
 			{
-				if (!(call.Method.IsOperator && (call.Method.Name == "op_Increment" || call.Method.Name == "op_Decrement")))
+				if (!UserDefinedCompoundAssign.IsIncrementOrDecrement(call.Method, context.Settings))
 					continue;
 				if (call.Arguments.Count != 1)
 					continue;

ICSharpCode.Decompiler/IL/Transforms/TransformAssignment.cs

@@ -392,7 +392,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 				}
 				else if (operatorCall.Arguments.Count == 1)
 				{
-					if (!(operatorCall.Method.Name == "op_Increment" || operatorCall.Method.Name == "op_Decrement"))
+					if (!UserDefinedCompoundAssign.IsIncrementOrDecrement(operatorCall.Method, context.Settings))
 						return false;
 					// use a dummy node so that we don't need a dedicated instruction for user-defined unary operator calls
 					rhs = new LdcI4(1);
@@ -988,7 +988,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			{
 				if (!operatorCall.Arguments[0].MatchLdLoc(tmpVar))
 					return false;
-				if (!(operatorCall.Method.Name == "op_Increment" || operatorCall.Method.Name == "op_Decrement"))
+				if (!UserDefinedCompoundAssign.IsIncrementOrDecrement(operatorCall.Method, context.Settings))
 					return false;
 				if (operatorCall.IsLifted)
 					return false; // TODO: add tests and think about whether nullables need special considerations

ILSpy/Properties/Resources.resx

@@ -279,6 +279,9 @@ Are you sure you want to continue?</value>
   <data name="DecompilerSettings.AsyncEnumerator" xml:space="preserve">
     <value>Decompile async IAsyncEnumerator methods</value>
   </data>
+  <data name="DecompilerSettings.CheckedOperators" xml:space="preserve">
+    <value>User-defined checked operators</value>
+  </data>
   <data name="DecompilerSettings.DecompileAnonymousMethodsLambdas" xml:space="preserve">
     <value>Decompile anonymous methods/lambdas</value>
   </data>
@@ -1069,7 +1072,4 @@ Do you want to continue?</value>
   <data name="_Window" xml:space="preserve">
     <value>_Window</value>
   </data>
-  <data name="DecompilerSettings.CheckedOperators" xml:space="preserve">
-    <value>User-defined checked operators</value>
-  </data>
 </root>