Fix #1698: Readonly auto properties from VB.NET are not properly decompiled

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

@@ -107,6 +107,7 @@
     <Compile Include="TestCases\Correctness\DeconstructionTests.cs" />
     <Compile Include="TestCases\Correctness\DynamicTests.cs" />
     <Compile Include="TestCases\Correctness\StringConcat.cs" />
+    <Compile Include="TestCases\VBPretty\VBPropertiesTest.cs" />
     <None Include="TestCases\ILPretty\Issue2260SwitchString.cs" />
     <None Include="TestCases\Pretty\Records.cs" />
     <Compile Include="TestCases\VBPretty\Issue2192.cs" />
@@ -308,6 +309,7 @@
     <None Include="TestCases\Pretty\Readme.txt" />
     <None Include="TestCases\VBPretty\VBCompoundAssign.vb" />
     <None Include="TestCases\VBPretty\Async.vb" />
+    <None Include="TestCases\VBPretty\VBPropertiesTest.vb" />
   </ItemGroup>
 
   <ItemGroup>

ICSharpCode.Decompiler.Tests/TestCases/ILPretty/Issue1325.cs

@@ -1,6 +1,5 @@
 using System;
 using System.ComponentModel;
-using System.Diagnostics;
 using System.IO;
 using System.Reflection;
 using System.Runtime.CompilerServices;
@@ -13,6 +12,8 @@ using Microsoft.VisualBasic.CompilerServices;
 [assembly: AssemblyConfiguration("Debug")]
 [assembly: AssemblyFileVersion("1.0.0.0")]
 
+#pragma warning disable format 
+
 namespace Issue1325
 {
 	[StandardModule]
@@ -34,9 +35,6 @@ namespace Issue1325
 
 	internal class Test
 	{
-		[DebuggerBrowsable(DebuggerBrowsableState.Never)]
-		[CompilerGenerated]
-		private string _Unparameterized;
 		public string Parameterized {
 			get {
 				throw new NotImplementedException();

ICSharpCode.Decompiler.Tests/TestCases/VBPretty/VBPropertiesTest.cs

@@ -0,0 +1,39 @@
+using System;
+
+public class VBPropertiesTest
+{
+	private int _fullProperty;
+
+	public int FullProperty {
+		get {
+			return _fullProperty;
+		}
+		set {
+			_fullProperty = value;
+		}
+	}
+
+	public int AutoProperty { get; set; }
+
+#if ROSLYN
+	public int ReadOnlyAutoProperty { get; }
+	public VBPropertiesTest()
+	{
+		ReadOnlyAutoProperty = 32;
+	}
+#endif
+
+	public void TestMethod()
+	{
+		FullProperty = 42;
+		_fullProperty = 24;
+		AutoProperty = 4711;
+
+		Console.WriteLine(AutoProperty);
+		Console.WriteLine(_fullProperty);
+		Console.WriteLine(FullProperty);
+#if ROSLYN
+		Console.WriteLine(ReadOnlyAutoProperty);
+#endif
+	}
+}

ICSharpCode.Decompiler.Tests/TestCases/VBPretty/VBPropertiesTest.vb

@@ -0,0 +1,37 @@
+Imports System
+Public Class VBPropertiesTest
+	Private _fullProperty As Integer
+
+	Property FullProperty As Integer
+		Get
+			Return _fullProperty
+		End Get
+		Set(value As Integer)
+			_fullProperty = value
+		End Set
+	End Property
+
+	Property AutoProperty As Integer
+
+#If ROSLYN Then
+	ReadOnly Property ReadOnlyAutoProperty As Integer
+
+	Sub New()
+		Me.ReadOnlyAutoProperty = 32
+	End Sub
+#End If
+
+	Sub TestMethod()
+		Me.FullProperty = 42
+		Me._fullProperty = 24
+		Me.AutoProperty = 4711
+
+		Console.WriteLine(Me.AutoProperty)
+		Console.WriteLine(Me._fullProperty)
+		Console.WriteLine(Me.FullProperty)
+
+#If ROSLYN Then
+		Console.WriteLine(Me.ReadOnlyAutoProperty)
+#End If
+	End Sub
+End Class

ICSharpCode.Decompiler.Tests/VBPrettyTestRunner.cs

@@ -102,6 +102,12 @@ namespace ICSharpCode.Decompiler.Tests
 			Run(options: options | CompilerOptions.Library);
 		}
 
+		[Test]
+		public void VBPropertiesTest([ValueSource(nameof(defaultOptions))] CompilerOptions options)
+		{
+			Run(options: options | CompilerOptions.Library);
+		}
+
 		void Run([CallerMemberName] string testName = null, CompilerOptions options = CompilerOptions.UseDebug, DecompilerSettings settings = null)
 		{
 			var vbFile = Path.Combine(TestCasePath, testName + ".vb");
@@ -115,7 +121,7 @@ namespace ICSharpCode.Decompiler.Tests
 			var executable = Tester.CompileVB(vbFile, options | CompilerOptions.ReferenceVisualBasic, exeFile);
 			var decompiled = Tester.DecompileCSharp(executable.PathToAssembly, settings);
 
-			CodeAssert.FilesAreEqual(csFile, decompiled);
+			CodeAssert.FilesAreEqual(csFile, decompiled, Tester.GetPreprocessorSymbols(options).ToArray());
 		}
 	}
 }

ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs

@@ -386,7 +386,7 @@ namespace ICSharpCode.Decompiler.CSharp
 		static readonly Regex automaticPropertyBackingFieldRegex = new Regex(@"^<(.*)>k__BackingField$",
 			RegexOptions.Compiled | RegexOptions.CultureInvariant);
 
-		static bool IsAutomaticPropertyBackingField(SRM.FieldDefinition field, MetadataReader metadata, out string propertyName)
+		static bool IsAutomaticPropertyBackingField(FieldDefinition field, MetadataReader metadata, out string propertyName)
 		{
 			propertyName = null;
 			var name = metadata.GetString(field.Name);
@@ -396,6 +396,11 @@ namespace ICSharpCode.Decompiler.CSharp
 				propertyName = m.Groups[1].Value;
 				return true;
 			}
+			if (name.StartsWith("_", StringComparison.Ordinal))
+			{
+				propertyName = name.Substring(1);
+				return field.GetCustomAttributes().HasKnownAttribute(metadata, KnownAttribute.CompilerGenerated);
+			}
 			return false;
 		}
 

ICSharpCode.Decompiler/CSharp/Transforms/PatternStatementTransform.cs

@@ -592,15 +592,15 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 			}
 		};
 
-		bool CanTransformToAutomaticProperty(IProperty property)
+		bool CanTransformToAutomaticProperty(IProperty property, bool accessorsMustBeCompilerGenerated)
 		{
 			if (!property.CanGet)
 				return false;
-			if (!property.Getter.IsCompilerGenerated())
+			if (accessorsMustBeCompilerGenerated && !property.Getter.IsCompilerGenerated())
 				return false;
 			if (property.Setter is IMethod setter)
 			{
-				if (!setter.IsCompilerGenerated())
+				if (accessorsMustBeCompilerGenerated && !setter.IsCompilerGenerated())
 					return false;
 				if (setter.HasReadonlyModifier())
 					return false;
@@ -611,7 +611,7 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 		PropertyDeclaration TransformAutomaticProperty(PropertyDeclaration propertyDeclaration)
 		{
 			IProperty property = propertyDeclaration.GetSymbol() as IProperty;
-			if (!CanTransformToAutomaticProperty(property))
+			if (!CanTransformToAutomaticProperty(property, !property.DeclaringTypeDefinition.Fields.Any(f => f.Name == "_" + property.Name && f.IsCompilerGenerated())))
 				return null;
 			IField field = null;
 			Match m = automaticPropertyPattern.Match(propertyDeclaration);
@@ -741,7 +741,8 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 				var mrr = parent.Annotation<MemberResolveResult>();
 				var field = mrr?.Member as IField;
 				if (field != null && IsBackingFieldOfAutomaticProperty(field, out var property)
-					&& CanTransformToAutomaticProperty(property) && currentMethod.AccessorOwner != property)
+					&& CanTransformToAutomaticProperty(property, !(field.IsCompilerGenerated() && field.Name == "_" + property.Name))
+					&& currentMethod.AccessorOwner != property)
 				{
 					if (!property.CanSet && !context.Settings.GetterOnlyAutomaticProperties)
 						return null;