Support "where T : unmanaged" constraints.

ICSharpCode.Decompiler.Tests/Helpers/RemoveCompilerAttribute.cs

@@ -33,11 +33,12 @@ namespace ICSharpCode.Decompiler.Tests.Helpers
 		}
 	}
 
-	public class RemoveEmbeddedAtttributes : DepthFirstAstVisitor, IAstTransform
+	public class RemoveEmbeddedAttributes : DepthFirstAstVisitor, IAstTransform
 	{
 		HashSet<string> attributeNames = new HashSet<string>() {
 			"System.Runtime.CompilerServices.IsReadOnlyAttribute",
 			"System.Runtime.CompilerServices.IsByRefLikeAttribute",
+			"System.Runtime.CompilerServices.IsUnmanagedAttribute",
 			"Microsoft.CodeAnalysis.EmbeddedAttribute",
 		};
 

ICSharpCode.Decompiler.Tests/Helpers/Tester.cs

@@ -412,7 +412,7 @@ namespace ICSharpCode.Decompiler.Tests.Helpers
 				resolver.AddSearchDirectory(Path.GetDirectoryName(typeof(Span<>).Assembly.Location));
 				var typeSystem = new DecompilerTypeSystem(module, resolver, settings);
 				CSharpDecompiler decompiler = new CSharpDecompiler(typeSystem, settings);
-				decompiler.AstTransforms.Insert(0, new RemoveEmbeddedAtttributes());
+				decompiler.AstTransforms.Insert(0, new RemoveEmbeddedAttributes());
 				decompiler.AstTransforms.Insert(0, new RemoveCompilerAttribute());
 				decompiler.AstTransforms.Add(new EscapeInvalidIdentifiers());
 				var syntaxTree = decompiler.DecompileWholeModuleAsSingleFile();

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

@@ -32,7 +32,11 @@
   </PropertyGroup>
 
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|AnyCPU'">
-    <DefineConstants>TRACE;DEBUG;NET46;ROSLYN;CS60;CS70</DefineConstants>
+    <DefineConstants>TRACE;DEBUG;NET46;ROSLYN;CS60;CS70;CS71;CS72;CS73</DefineConstants>
+  </PropertyGroup>
+
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|AnyCPU'">
+    <DefineConstants>TRACE;NET46;ROSLYN;CS60;CS70;CS71;CS72;CS73</DefineConstants>
   </PropertyGroup>
 
   <ItemGroup>

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

@@ -96,5 +96,22 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 		{
 			return new T[size1, size2];
 		}
+
+#if CS73
+		public static object CallDelegate<T>(T input) where T : Delegate
+		{
+			return input.DynamicInvoke();
+		}
+
+		public static int CountEnumerators<T>() where T : Enum
+		{
+			return typeof(T).GetEnumValues().Length;
+		}
+
+		public unsafe static int UnmanagedConstraint<T>() where T : unmanaged
+		{
+			return sizeof(T);
+		}
+#endif
 	}
 }

ICSharpCode.Decompiler.Tests/TestCases/Pretty/Generics.opt.roslyn.il

@@ -33,6 +33,40 @@
 
 // =============== CLASS MEMBERS DECLARATION ===================
 
+.class private auto ansi sealed beforefieldinit Microsoft.CodeAnalysis.EmbeddedAttribute
+       extends [mscorlib]System.Attribute
+{
+  .custom instance void [mscorlib]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = ( 01 00 00 00 ) 
+  .custom instance void Microsoft.CodeAnalysis.EmbeddedAttribute::.ctor() = ( 01 00 00 00 ) 
+  .method public hidebysig specialname rtspecialname 
+          instance void  .ctor() cil managed
+  {
+    // Code size       7 (0x7)
+    .maxstack  8
+    IL_0000:  ldarg.0
+    IL_0001:  call       instance void [mscorlib]System.Attribute::.ctor()
+    IL_0006:  ret
+  } // end of method EmbeddedAttribute::.ctor
+
+} // end of class Microsoft.CodeAnalysis.EmbeddedAttribute
+
+.class private auto ansi sealed beforefieldinit System.Runtime.CompilerServices.IsUnmanagedAttribute
+       extends [mscorlib]System.Attribute
+{
+  .custom instance void [mscorlib]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = ( 01 00 00 00 ) 
+  .custom instance void Microsoft.CodeAnalysis.EmbeddedAttribute::.ctor() = ( 01 00 00 00 ) 
+  .method public hidebysig specialname rtspecialname 
+          instance void  .ctor() cil managed
+  {
+    // Code size       7 (0x7)
+    .maxstack  8
+    IL_0000:  ldarg.0
+    IL_0001:  call       instance void [mscorlib]System.Attribute::.ctor()
+    IL_0006:  ret
+  } // end of method IsUnmanagedAttribute::.ctor
+
+} // end of class System.Runtime.CompilerServices.IsUnmanagedAttribute
+
 .class private auto ansi beforefieldinit ICSharpCode.Decompiler.Tests.TestCases.Pretty.Generics
        extends [mscorlib]System.Object
 {
@@ -222,6 +256,40 @@
     IL_0007:  ret
   } // end of method Generics::NewArray
 
+  .method public hidebysig static object 
+          CallDelegate<([mscorlib]System.Delegate) T>(!!T input) cil managed
+  {
+    // Code size       18 (0x12)
+    .maxstack  8
+    IL_0000:  ldarg.0
+    IL_0001:  box        !!T
+    IL_0006:  ldc.i4.0
+    IL_0007:  newarr     [mscorlib]System.Object
+    IL_000c:  callvirt   instance object [mscorlib]System.Delegate::DynamicInvoke(object[])
+    IL_0011:  ret
+  } // end of method Generics::CallDelegate
+
+  .method public hidebysig static int32  CountEnumerators<([mscorlib]System.Enum) T>() cil managed
+  {
+    // Code size       21 (0x15)
+    .maxstack  8
+    IL_0000:  ldtoken    !!T
+    IL_0005:  call       class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
+    IL_000a:  callvirt   instance class [mscorlib]System.Array [mscorlib]System.Type::GetEnumValues()
+    IL_000f:  callvirt   instance int32 [mscorlib]System.Array::get_Length()
+    IL_0014:  ret
+  } // end of method Generics::CountEnumerators
+
+  .method public hidebysig static int32  UnmanagedConstraint<valuetype .ctor (class [mscorlib]System.ValueType modreq([mscorlib]System.Runtime.InteropServices.UnmanagedType)) T>() cil managed
+  {
+    .param type T 
+    .custom instance void System.Runtime.CompilerServices.IsUnmanagedAttribute::.ctor() = ( 01 00 00 00 ) 
+    // Code size       7 (0x7)
+    .maxstack  8
+    IL_0000:  sizeof     !!T
+    IL_0006:  ret
+  } // end of method Generics::UnmanagedConstraint
+
   .method public hidebysig specialname rtspecialname 
           instance void  .ctor() cil managed
   {

ICSharpCode.Decompiler.Tests/TestCases/Pretty/Generics.roslyn.il

@@ -33,6 +33,42 @@
 
 // =============== CLASS MEMBERS DECLARATION ===================
 
+.class private auto ansi sealed beforefieldinit Microsoft.CodeAnalysis.EmbeddedAttribute
+       extends [mscorlib]System.Attribute
+{
+  .custom instance void [mscorlib]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = ( 01 00 00 00 ) 
+  .custom instance void Microsoft.CodeAnalysis.EmbeddedAttribute::.ctor() = ( 01 00 00 00 ) 
+  .method public hidebysig specialname rtspecialname 
+          instance void  .ctor() cil managed
+  {
+    // Code size       8 (0x8)
+    .maxstack  8
+    IL_0000:  ldarg.0
+    IL_0001:  call       instance void [mscorlib]System.Attribute::.ctor()
+    IL_0006:  nop
+    IL_0007:  ret
+  } // end of method EmbeddedAttribute::.ctor
+
+} // end of class Microsoft.CodeAnalysis.EmbeddedAttribute
+
+.class private auto ansi sealed beforefieldinit System.Runtime.CompilerServices.IsUnmanagedAttribute
+       extends [mscorlib]System.Attribute
+{
+  .custom instance void [mscorlib]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = ( 01 00 00 00 ) 
+  .custom instance void Microsoft.CodeAnalysis.EmbeddedAttribute::.ctor() = ( 01 00 00 00 ) 
+  .method public hidebysig specialname rtspecialname 
+          instance void  .ctor() cil managed
+  {
+    // Code size       8 (0x8)
+    .maxstack  8
+    IL_0000:  ldarg.0
+    IL_0001:  call       instance void [mscorlib]System.Attribute::.ctor()
+    IL_0006:  nop
+    IL_0007:  ret
+  } // end of method IsUnmanagedAttribute::.ctor
+
+} // end of class System.Runtime.CompilerServices.IsUnmanagedAttribute
+
 .class private auto ansi beforefieldinit ICSharpCode.Decompiler.Tests.TestCases.Pretty.Generics
        extends [mscorlib]System.Object
 {
@@ -298,6 +334,58 @@
     IL_000c:  ret
   } // end of method Generics::NewArray
 
+  .method public hidebysig static object 
+          CallDelegate<([mscorlib]System.Delegate) T>(!!T input) cil managed
+  {
+    // Code size       23 (0x17)
+    .maxstack  2
+    .locals init (object V_0)
+    IL_0000:  nop
+    IL_0001:  ldarg.0
+    IL_0002:  box        !!T
+    IL_0007:  ldc.i4.0
+    IL_0008:  newarr     [mscorlib]System.Object
+    IL_000d:  callvirt   instance object [mscorlib]System.Delegate::DynamicInvoke(object[])
+    IL_0012:  stloc.0
+    IL_0013:  br.s       IL_0015
+
+    IL_0015:  ldloc.0
+    IL_0016:  ret
+  } // end of method Generics::CallDelegate
+
+  .method public hidebysig static int32  CountEnumerators<([mscorlib]System.Enum) T>() cil managed
+  {
+    // Code size       26 (0x1a)
+    .maxstack  1
+    .locals init (int32 V_0)
+    IL_0000:  nop
+    IL_0001:  ldtoken    !!T
+    IL_0006:  call       class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
+    IL_000b:  callvirt   instance class [mscorlib]System.Array [mscorlib]System.Type::GetEnumValues()
+    IL_0010:  callvirt   instance int32 [mscorlib]System.Array::get_Length()
+    IL_0015:  stloc.0
+    IL_0016:  br.s       IL_0018
+
+    IL_0018:  ldloc.0
+    IL_0019:  ret
+  } // end of method Generics::CountEnumerators
+
+  .method public hidebysig static int32  UnmanagedConstraint<valuetype .ctor (class [mscorlib]System.ValueType modreq([mscorlib]System.Runtime.InteropServices.UnmanagedType)) T>() cil managed
+  {
+    .param type T 
+    .custom instance void System.Runtime.CompilerServices.IsUnmanagedAttribute::.ctor() = ( 01 00 00 00 ) 
+    // Code size       12 (0xc)
+    .maxstack  1
+    .locals init (int32 V_0)
+    IL_0000:  nop
+    IL_0001:  sizeof     !!T
+    IL_0007:  stloc.0
+    IL_0008:  br.s       IL_000a
+
+    IL_000a:  ldloc.0
+    IL_000b:  ret
+  } // end of method Generics::UnmanagedConstraint
+
   .method public hidebysig specialname rtspecialname 
           instance void  .ctor() cil managed
   {

ICSharpCode.Decompiler/CSharp/Syntax/TypeSystemAstBuilder.cs

@@ -1730,7 +1730,11 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 					c.BaseTypes.Add(new PrimitiveType("class"));
 				}
 			} else if (tp.HasValueTypeConstraint) {
-				c.BaseTypes.Add(new PrimitiveType("struct"));
+				if (tp.HasUnmanagedConstraint) {
+					c.BaseTypes.Add(new PrimitiveType("unmanaged"));
+				} else {
+					c.BaseTypes.Add(new PrimitiveType("struct"));
+				}
 			}
 			foreach (IType t in tp.DirectBaseTypes) {
 				if (!IsObjectOrValueType(t))

ICSharpCode.Decompiler/DecompilerSettings.cs

@@ -89,7 +89,7 @@ namespace ICSharpCode.Decompiler
 				nonTrailingNamedArguments = false;
 			}
 			if (languageVersion < CSharp.LanguageVersion.CSharp7_3) {
-				//introduceUnmanagedTypeConstraint = false;
+				introduceUnmanagedConstraint = false;
 				stackAllocInitializers = false;
 				tupleComparisons = false;
 			}
@@ -100,7 +100,7 @@ namespace ICSharpCode.Decompiler
 
 		public CSharp.LanguageVersion GetMinimumRequiredVersion()
 		{
-			if (tupleComparisons || stackAllocInitializers)
+			if (introduceUnmanagedConstraint || tupleComparisons || stackAllocInitializers)
 				return CSharp.LanguageVersion.CSharp7_3;
 			if (introduceRefModifiersOnStructs || introduceReadonlyAndInModifiers || nonTrailingNamedArguments)
 				return CSharp.LanguageVersion.CSharp7_2;
@@ -687,6 +687,22 @@ namespace ICSharpCode.Decompiler
 			}
 		}
 
+		bool introduceUnmanagedConstraint = true;
+
+		/// <summary>
+		/// If this option is active, [IsUnmanagedAttribute] on type parameters
+		/// is replaced with "T : unmanaged" constraints.
+		/// </summary>
+		public bool IntroduceUnmanagedConstraint {
+			get { return introduceUnmanagedConstraint; }
+			set {
+				if (introduceUnmanagedConstraint != value) {
+					introduceUnmanagedConstraint = value;
+					OnPropertyChanged();
+				}
+			}
+		}
+
 		bool stackAllocInitializers = true;
 
 		/// <summary>

ICSharpCode.Decompiler/TypeSystem/DecompilerTypeSystem.cs

@@ -94,14 +94,20 @@ namespace ICSharpCode.Decompiler.TypeSystem
 		/// </summary>
 		RefStructs = 0x100,
 		/// <summary>
+		/// If this option is active, [IsUnmanagedAttribute] is removed from type parameters,
+		/// and HasUnmanagedConstraint is set instead.
+		/// </summary>
+		UnmanagedConstraints = 0x200,
+		/// <summary>
 		/// If this option is active, [NullableAttribute] is removed and reference types with
 		/// nullability annotations are used instead.
 		/// </summary>
-		NullabilityAnnotations = 0x200,
+		NullabilityAnnotations = 0x400,
 		/// <summary>
 		/// Default settings: typical options for the decompiler, with all C# languages features enabled.
 		/// </summary>
-		Default = Dynamic | Tuple | ExtensionMethods | DecimalConstants | ReadOnlyStructsAndParameters | RefStructs
+		Default = Dynamic | Tuple | ExtensionMethods | DecimalConstants | ReadOnlyStructsAndParameters
+			| RefStructs | UnmanagedConstraints | NullabilityAnnotations
 	}
 
 	/// <summary>
@@ -127,6 +133,8 @@ namespace ICSharpCode.Decompiler.TypeSystem
 				typeSystemOptions |= TypeSystemOptions.RefStructs;
 			if (settings.IntroduceReadonlyAndInModifiers)
 				typeSystemOptions |= TypeSystemOptions.ReadOnlyStructsAndParameters;
+			if (settings.IntroduceUnmanagedConstraint)
+				typeSystemOptions |= TypeSystemOptions.UnmanagedConstraints;
 			if (settings.NullableReferenceTypes)
 				typeSystemOptions |= TypeSystemOptions.NullabilityAnnotations;
 			return typeSystemOptions;

ICSharpCode.Decompiler/TypeSystem/ITypeParameter.cs

@@ -83,10 +83,15 @@ namespace ICSharpCode.Decompiler.TypeSystem
 		bool HasReferenceTypeConstraint { get; }
 		
 		/// <summary>
-		/// Gets if the type parameter has the 'struct' constraint.
+		/// Gets if the type parameter has the 'struct' or 'unmanaged' constraint.
 		/// </summary>
 		bool HasValueTypeConstraint { get; }
 
+		/// <summary>
+		/// Gets if the type parameter has the 'unmanaged' constraint.
+		/// </summary>
+		bool HasUnmanagedConstraint { get; }
+
 		/// <summary>
 		/// Nullability of the reference type constraint. (e.g. "where T : class?").
 		/// 

ICSharpCode.Decompiler/TypeSystem/Implementation/AbstractTypeParameter.cs

@@ -158,6 +158,7 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 		public abstract bool HasDefaultConstructorConstraint { get; }
 		public abstract bool HasReferenceTypeConstraint { get; }
 		public abstract bool HasValueTypeConstraint { get; }
+		public abstract bool HasUnmanagedConstraint { get; }
 		public abstract Nullability NullabilityConstraint { get; }
 
 		public TypeKind Kind {

ICSharpCode.Decompiler/TypeSystem/Implementation/AttributeListBuilder.cs

@@ -169,7 +169,7 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 		#endregion
 
 		#region Custom Attributes (ReadAttribute)
-		public void Add(CustomAttributeHandleCollection attributes)
+		public void Add(CustomAttributeHandleCollection attributes, SymbolKind target)
 		{
 			var metadata = module.metadata;
 			foreach (var handle in attributes) {
@@ -177,14 +177,14 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 				// Attribute types shouldn't be generic (and certainly not open), so we don't need a generic context.
 				var ctor = module.ResolveMethod(attribute.Constructor, new GenericContext());
 				var type = ctor.DeclaringType;
-				if (IgnoreAttribute(type)) {
+				if (IgnoreAttribute(type, target)) {
 					continue;
 				}
 				Add(new CustomAttribute(module, ctor, handle));
 			}
 		}
 
-		bool IgnoreAttribute(IType attributeType)
+		bool IgnoreAttribute(IType attributeType, SymbolKind target)
 		{
 			if (attributeType.DeclaringType != null || attributeType.TypeParameterCount != 0)
 				return false;
@@ -199,18 +199,20 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 						case "ExtensionAttribute":
 							return (options & TypeSystemOptions.ExtensionMethods) != 0;
 						case "DecimalConstantAttribute":
-							return (options & TypeSystemOptions.DecimalConstants) != 0;
+							return (options & TypeSystemOptions.DecimalConstants) != 0 && target == SymbolKind.Field;
 						case "IsReadOnlyAttribute":
 							return (options & TypeSystemOptions.ReadOnlyStructsAndParameters) != 0;
 						case "IsByRefLikeAttribute":
-							return (options & TypeSystemOptions.RefStructs) != 0;
+							return (options & TypeSystemOptions.RefStructs) != 0 && target == SymbolKind.TypeDefinition;
+						case "IsUnmanagedAttribute":
+							return (options & TypeSystemOptions.UnmanagedConstraints) != 0 && target == SymbolKind.TypeParameter;
 						case "NullableAttribute":
 							return (options & TypeSystemOptions.NullabilityAnnotations) != 0;
 						default:
 							return false;
 					}
 				case "System":
-					return attributeType.Name == "ParamArrayAttribute";
+					return attributeType.Name == "ParamArrayAttribute" && target == SymbolKind.Parameter;
 				default:
 					return false;
 			}

ICSharpCode.Decompiler/TypeSystem/Implementation/DefaultTypeParameter.cs

@@ -69,6 +69,7 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 		public override bool HasValueTypeConstraint => hasValueTypeConstraint;
 		public override bool HasReferenceTypeConstraint => hasReferenceTypeConstraint;
 		public override bool HasDefaultConstructorConstraint => hasDefaultConstructorConstraint;
+		public override bool HasUnmanagedConstraint => false;
 		public override Nullability NullabilityConstraint => nullabilityConstraint;
 
 		public override IEnumerable<IType> DirectBaseTypes {

ICSharpCode.Decompiler/TypeSystem/Implementation/DummyTypeParameter.cs

@@ -163,20 +163,10 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 			get { return EmptyList<IType>.Instance; }
 		}
 
-		bool ITypeParameter.HasDefaultConstructorConstraint {
-			get { return false; }
-		}
-		
-		bool ITypeParameter.HasReferenceTypeConstraint {
-			get { return false; }
-		}
-		
-		bool ITypeParameter.HasValueTypeConstraint {
-			get { return false; }
-		}
-
-		Nullability ITypeParameter.NullabilityConstraint {
-			get { return Nullability.Oblivious; }
-		}
+		bool ITypeParameter.HasDefaultConstructorConstraint => false;
+		bool ITypeParameter.HasReferenceTypeConstraint => false;
+		bool ITypeParameter.HasValueTypeConstraint => false;
+		bool ITypeParameter.HasUnmanagedConstraint => false;
+		Nullability ITypeParameter.NullabilityConstraint => Nullability.Oblivious;
 	}
 }

ICSharpCode.Decompiler/TypeSystem/Implementation/KnownAttributes.cs

@@ -86,6 +86,9 @@ namespace ICSharpCode.Decompiler.TypeSystem
 		CallerFilePath,
 		CallerLineNumber,
 
+		// Type parameter attributes:
+		IsUnmanaged,
+
 		// Marshalling attributes:
 		MarshalAs,
 
@@ -143,6 +146,8 @@ namespace ICSharpCode.Decompiler.TypeSystem
 			new TopLevelTypeName("System.Runtime.CompilerServices", nameof(CallerMemberNameAttribute)),
 			new TopLevelTypeName("System.Runtime.CompilerServices", nameof(CallerFilePathAttribute)),
 			new TopLevelTypeName("System.Runtime.CompilerServices", nameof(CallerLineNumberAttribute)),
+			// Type parameter attributes:
+			new TopLevelTypeName("System.Runtime.CompilerServices", "IsUnmanagedAttribute"),
 			// Marshalling attributes:
 			new TopLevelTypeName("System.Runtime.InteropServices", nameof(MarshalAsAttribute)),
 			// Security attributes:

ICSharpCode.Decompiler/TypeSystem/Implementation/MetadataEvent.cs

@@ -107,7 +107,7 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 			var b = new AttributeListBuilder(module);
 			var metadata = module.metadata;
 			var eventDef = metadata.GetEventDefinition(handle);
-			b.Add(eventDef.GetCustomAttributes());
+			b.Add(eventDef.GetCustomAttributes(), SymbolKind.Event);
 			return b.Build();
 		}
 		#endregion

ICSharpCode.Decompiler/TypeSystem/Implementation/MetadataField.cs

@@ -146,7 +146,7 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 			}
 
 			b.AddMarshalInfo(fieldDef.GetMarshallingDescriptor());
-			b.Add(fieldDef.GetCustomAttributes());
+			b.Add(fieldDef.GetCustomAttributes(), SymbolKind.Field);
 
 			return b.Build();
 		}

ICSharpCode.Decompiler/TypeSystem/Implementation/MetadataMethod.cs

@@ -363,7 +363,7 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 			}
 			#endregion
 
-			b.Add(def.GetCustomAttributes());
+			b.Add(def.GetCustomAttributes(), symbolKind);
 			b.AddSecurityAttributes(def.GetDeclarativeSecurityAttributes());
 
 			return b.Build();
@@ -381,7 +381,7 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 				var retParam = metadata.GetParameter(parameters.First());
 				if (retParam.SequenceNumber == 0) {
 					b.AddMarshalInfo(retParam.GetMarshallingDescriptor());
-					b.Add(retParam.GetCustomAttributes());
+					b.Add(retParam.GetCustomAttributes(), symbolKind);
 				}
 			}
 			return b.Build();

ICSharpCode.Decompiler/TypeSystem/Implementation/MetadataParameter.cs

@@ -72,7 +72,7 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 				if ((attributes & ParameterAttributes.Out) == ParameterAttributes.Out)
 					b.Add(KnownAttribute.Out);
 			}
-			b.Add(parameter.GetCustomAttributes());
+			b.Add(parameter.GetCustomAttributes(), SymbolKind.Parameter);
 			b.AddMarshalInfo(parameter.GetMarshallingDescriptor());
 
 			return b.Build();

ICSharpCode.Decompiler/TypeSystem/Implementation/MetadataProperty.cs

@@ -155,7 +155,7 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 			if (IsIndexer && Name != "Item" && !IsExplicitInterfaceImplementation) {
 				b.Add(KnownAttribute.IndexerName, KnownTypeCode.String, Name);
 			}
-			b.Add(propertyDef.GetCustomAttributes());
+			b.Add(propertyDef.GetCustomAttributes(), symbolKind);
 			return b.Build();
 		}
 		#endregion

ICSharpCode.Decompiler/TypeSystem/Implementation/MetadataTypeDefinition.cs

@@ -372,7 +372,7 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 			}
 			#endregion
 
-			b.Add(typeDefinition.GetCustomAttributes());
+			b.Add(typeDefinition.GetCustomAttributes(), SymbolKind.TypeDefinition);
 			b.AddSecurityAttributes(typeDefinition.GetDeclarativeSecurityAttributes());
 
 			return b.Build();

ICSharpCode.Decompiler/TypeSystem/Implementation/MetadataTypeParameter.cs

@@ -35,6 +35,7 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 
 		// lazy-loaded:
 		IReadOnlyList<IType> constraints;
+		byte unmanagedConstraint = ThreeState.Unknown;
 		const byte nullabilityNotYetLoaded = 255;
 		byte nullabilityConstraint = nullabilityNotYetLoaded;
 
@@ -106,7 +107,7 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 
 			var attributes = gp.GetCustomAttributes();
 			var b = new AttributeListBuilder(module, attributes.Count);
-			b.Add(attributes);
+			b.Add(attributes, SymbolKind.TypeParameter);
 			return b.Build();
 		}
 
@@ -114,6 +115,24 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 		public override bool HasReferenceTypeConstraint => (attr & GenericParameterAttributes.ReferenceTypeConstraint) != 0;
 		public override bool HasValueTypeConstraint => (attr & GenericParameterAttributes.NotNullableValueTypeConstraint) != 0;
 
+		public override bool HasUnmanagedConstraint {
+			get {
+				if (unmanagedConstraint == ThreeState.Unknown) {
+					unmanagedConstraint = ThreeState.From(LoadUnmanagedConstraint());
+				}
+				return unmanagedConstraint == ThreeState.True;
+			}
+		}
+
+		private bool LoadUnmanagedConstraint()
+		{
+			if ((module.TypeSystemOptions & TypeSystemOptions.UnmanagedConstraints) == 0)
+				return false;
+			var metadata = module.metadata;
+			var gp = metadata.GetGenericParameter(handle);
+			return gp.GetCustomAttributes().HasKnownAttribute(metadata, KnownAttribute.IsUnmanaged);
+		}
+
 		public override Nullability NullabilityConstraint {
 			get {
 				if (nullabilityConstraint == nullabilityNotYetLoaded) {

ICSharpCode.Decompiler/TypeSystem/Implementation/NullabilityAnnotatedType.cs

@@ -90,6 +90,7 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 		bool ITypeParameter.HasDefaultConstructorConstraint => baseType.HasDefaultConstructorConstraint;
 		bool ITypeParameter.HasReferenceTypeConstraint => baseType.HasReferenceTypeConstraint;
 		bool ITypeParameter.HasValueTypeConstraint => baseType.HasValueTypeConstraint;
+		bool ITypeParameter.HasUnmanagedConstraint => baseType.HasUnmanagedConstraint;
 		Nullability ITypeParameter.NullabilityConstraint => baseType.NullabilityConstraint;
 		SymbolKind ISymbol.SymbolKind => SymbolKind.TypeParameter;
 		IEnumerable<IAttribute> ITypeParameter.GetAttributes() => baseType.GetAttributes();

ICSharpCode.Decompiler/TypeSystem/Implementation/SpecializedMethod.cs

@@ -242,17 +242,10 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 				return o != null && baseTp.Equals(o.baseTp) && this.Owner.Equals(o.Owner);
 			}
 			
-			public override bool HasValueTypeConstraint {
-				get { return baseTp.HasValueTypeConstraint; }
-			}
-			
-			public override bool HasReferenceTypeConstraint {
-				get { return baseTp.HasReferenceTypeConstraint; }
-			}
-			
-			public override bool HasDefaultConstructorConstraint {
-				get { return baseTp.HasDefaultConstructorConstraint; }
-			}
+			public override bool HasValueTypeConstraint => baseTp.HasValueTypeConstraint;
+			public override bool HasReferenceTypeConstraint => baseTp.HasReferenceTypeConstraint;
+			public override bool HasDefaultConstructorConstraint => baseTp.HasDefaultConstructorConstraint;
+			public override bool HasUnmanagedConstraint => baseTp.HasUnmanagedConstraint;
 
 			public override Nullability NullabilityConstraint => baseTp.NullabilityConstraint;
 

ICSharpCode.Decompiler/TypeSystem/MetadataModule.cs

@@ -598,7 +598,7 @@ namespace ICSharpCode.Decompiler.TypeSystem
 			var b = new AttributeListBuilder(this);
 			if (metadata.IsAssembly) {
 				var assembly = metadata.GetAssemblyDefinition();
-				b.Add(metadata.GetCustomAttributes(Handle.AssemblyDefinition));
+				b.Add(metadata.GetCustomAttributes(Handle.AssemblyDefinition), SymbolKind.Module);
 				b.AddSecurityAttributes(assembly.GetDeclarativeSecurityAttributes());
 
 				// AssemblyVersionAttribute
@@ -617,7 +617,7 @@ namespace ICSharpCode.Decompiler.TypeSystem
 		public IEnumerable<IAttribute> GetModuleAttributes()
 		{
 			var b = new AttributeListBuilder(this);
-			b.Add(metadata.GetCustomAttributes(Handle.ModuleDefinition));
+			b.Add(metadata.GetCustomAttributes(Handle.ModuleDefinition), SymbolKind.Module);
 			if (!metadata.IsAssembly) {
 				AddTypeForwarderAttributes(ref b);
 			}