Fix #2349: Use proper ExpressionType with DynamicCompoundAssign.

ICSharpCode.Decompiler.Tests/CorrectnessTestRunner.cs

@@ -331,6 +331,12 @@ namespace ICSharpCode.Decompiler.Tests
 			RunCS(options: options);
 		}
 
+		[Test]
+		public void DynamicTests([ValueSource(nameof(noMonoOptions))] CompilerOptions options)
+		{
+			RunCS(options: options);
+		}
+
 		[Test]
 		public void MiniJSON([ValueSource(nameof(defaultOptions))] CompilerOptions options)
 		{

ICSharpCode.Decompiler.Tests/ICSharpCode.Decompiler.Tests.csproj

@@ -105,6 +105,7 @@
     <Compile Include="ProjectDecompiler\TargetFrameworkTests.cs" />
     <Compile Include="TestAssemblyResolver.cs" />
     <Compile Include="TestCases\Correctness\DeconstructionTests.cs" />
+    <Compile Include="TestCases\Correctness\DynamicTests.cs" />
     <Compile Include="TestCases\Correctness\StringConcat.cs" />
     <None Include="TestCases\ILPretty\Issue2260SwitchString.cs" />
     <None Include="TestCases\Pretty\Records.cs" />

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

@@ -0,0 +1,35 @@
+using System;
+
+namespace ICSharpCode.Decompiler.Tests.TestCases.Correctness
+{
+	class DynamicTests
+	{
+		delegate void RefAction<T>(ref T arg);
+
+		static void Main(string[] args)
+		{
+			PrintResult((ref dynamic x) => x = x + 2.0, 5.0);
+			PrintResult((ref dynamic x) => x = x + 2.0, 5);
+			PrintResult((ref dynamic x) => x = x + 2, 5.0);
+			PrintResult((ref dynamic x) => x = x + 2, 5);
+			PrintResult((ref dynamic x) => x = x - 2.0, 5.0);
+			PrintResult((ref dynamic x) => x = x - 2.0, 5);
+			PrintResult((ref dynamic x) => x = x - 2, 5.0);
+			PrintResult((ref dynamic x) => x = x - 2, 5);
+			PrintResult((ref dynamic x) => x = x * 2.0, 5.0);
+			PrintResult((ref dynamic x) => x = x * 2.0, 5);
+			PrintResult((ref dynamic x) => x = x * 2, 5.0);
+			PrintResult((ref dynamic x) => x = x * 2, 5);
+			PrintResult((ref dynamic x) => x = x / 2.0, 5.0);
+			PrintResult((ref dynamic x) => x = x / 2.0, 5);
+			PrintResult((ref dynamic x) => x = x / 2, 5.0);
+			PrintResult((ref dynamic x) => x = x / 2, 5);
+		}
+
+		private static void PrintResult(RefAction<dynamic> p, dynamic arg)
+		{
+			p(ref arg);
+			Console.WriteLine(arg);
+		}
+	}
+}

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

@@ -4529,7 +4529,7 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 			return M()[name] -= 2u;
 		}
 
-		public uint CompoundAssignIndexerComplexIndex(string name)
+		public uint CompoundAssignIndexerComplexIndex()
 		{
 			return M()[ToString()] -= 2u;
 		}

ICSharpCode.Decompiler/IL/Transforms/TransformAssignment.cs

@@ -19,9 +19,9 @@
 using System;
 using System.Diagnostics;
 using System.Linq;
+using System.Linq.Expressions;
 
 using ICSharpCode.Decompiler.TypeSystem;
-using ICSharpCode.Decompiler.TypeSystem.Implementation;
 using ICSharpCode.Decompiler.Util;
 
 namespace ICSharpCode.Decompiler.IL.Transforms
@@ -384,7 +384,29 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 					return false;
 				context.Step($"Compound assignment (dynamic binary)", compoundStore);
 				finalizeMatch?.Invoke(context);
-				newInst = new DynamicCompoundAssign(dynamicBinaryOp.Operation, dynamicBinaryOp.BinderFlags, target, dynamicBinaryOp.LeftArgumentInfo, dynamicBinaryOp.Right, dynamicBinaryOp.RightArgumentInfo, targetKind);
+				newInst = new DynamicCompoundAssign(ToCompound(dynamicBinaryOp.Operation), dynamicBinaryOp.BinderFlags, target, dynamicBinaryOp.LeftArgumentInfo, dynamicBinaryOp.Right, dynamicBinaryOp.RightArgumentInfo, targetKind);
+
+				static ExpressionType ToCompound(ExpressionType from)
+				{
+					return from switch
+					{
+						ExpressionType.Add => ExpressionType.AddAssign,
+						ExpressionType.AddChecked => ExpressionType.AddAssignChecked,
+						ExpressionType.And => ExpressionType.AndAssign,
+						ExpressionType.Divide => ExpressionType.DivideAssign,
+						ExpressionType.ExclusiveOr => ExpressionType.ExclusiveOrAssign,
+						ExpressionType.LeftShift => ExpressionType.LeftShiftAssign,
+						ExpressionType.Modulo => ExpressionType.ModuloAssign,
+						ExpressionType.Multiply => ExpressionType.MultiplyAssign,
+						ExpressionType.MultiplyChecked => ExpressionType.MultiplyAssignChecked,
+						ExpressionType.Or => ExpressionType.OrAssign,
+						ExpressionType.Power => ExpressionType.PowerAssign,
+						ExpressionType.RightShift => ExpressionType.RightShiftAssign,
+						ExpressionType.Subtract => ExpressionType.SubtractAssign,
+						ExpressionType.SubtractChecked => ExpressionType.SubtractAssignChecked,
+						_ => from
+					};
+				}
 			}
 			else if (setterValue is Call concatCall && UserDefinedCompoundAssign.IsStringConcat(concatCall.Method))
 			{