#2823: Introduce `IType.GetDefinitionOrUnknown()` to allow better detection of async state-machines involving unknown types.

ICSharpCode.Decompiler/IL/ControlFlow/AsyncAwaitDecompiler.cs

@@ -234,14 +234,10 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 			taskType = function.Method.ReturnType;
 			builderType = startCall.Method.DeclaringType;
 			FullTypeName builderTypeName;
-			if (builderType?.GetDefinition() is { } builderTypeDef)
+			if (builderType?.GetDefinitionOrUnknown() is { } builderTypeDef)
 			{
 				builderTypeName = builderTypeDef.FullTypeName;
 			}
-			else if (builderType is UnknownType unknownBuilderType)
-			{
-				builderTypeName = unknownBuilderType.FullTypeName;
-			}
 			else
 			{
 				return false;

ICSharpCode.Decompiler/TypeSystem/FunctionPointerType.cs

@@ -132,6 +132,11 @@ namespace ICSharpCode.Decompiler.TypeSystem
 			}
 		}
 
+		public override ITypeDefinitionOrUnknown GetDefinitionOrUnknown()
+		{
+			return GetDefinition();
+		}
+
 		public override IType AcceptVisitor(TypeVisitor visitor)
 		{
 			return visitor.VisitFunctionPointerType(this);

ICSharpCode.Decompiler/TypeSystem/IType.cs

@@ -87,6 +87,12 @@ namespace ICSharpCode.Decompiler.TypeSystem
 		/// </summary>
 		ITypeDefinition? GetDefinition();
 
+		/// <summary>
+		/// Gets the underlying type definition or UnkownType, if unknown.
+		/// Can return null for types which do not have a type definition (for example arrays, pointers, type parameters).
+		/// </summary>
+		ITypeDefinitionOrUnknown? GetDefinitionOrUnknown();
+
 		/// <summary>
 		/// Gets the parent type, if this is a nested type.
 		/// Returns null for top-level types.

ICSharpCode.Decompiler/TypeSystem/ITypeDefinition.cs

@@ -23,10 +23,10 @@ using System.Collections.Generic;
 namespace ICSharpCode.Decompiler.TypeSystem
 {
 	/// <summary>
-	/// Represents a class, enum, interface, struct, delegate or VB module.
+	/// Represents a class, enum, interface, struct, delegate, record or VB module.
 	/// For partial classes, this represents the whole class.
 	/// </summary>
-	public interface ITypeDefinition : IType, IEntity
+	public interface ITypeDefinition : ITypeDefinitionOrUnknown, IType, IEntity
 	{
 		IReadOnlyList<ITypeDefinition> NestedTypes { get; }
 		IReadOnlyList<IMember> Members { get; }

ICSharpCode.Decompiler/TypeSystem/ITypeDefinitionOrUnknown.cs

@@ -0,0 +1,34 @@
+// Copyright (c) 2022 Siegfried Pammer
+// 
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this
+// software and associated documentation files (the "Software"), to deal in the Software
+// without restriction, including without limitation the rights to use, copy, modify, merge,
+// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
+// to whom the Software is furnished to do so, subject to the following conditions:
+// 
+// The above copyright notice and this permission notice shall be included in all copies or
+// substantial portions of the Software.
+// 
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
+// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+#nullable enable
+
+namespace ICSharpCode.Decompiler.TypeSystem
+{
+	/// <summary>
+	/// Represents a class, enum, interface, struct, delegate, record or unknown type.
+	/// For partial classes, this represents the whole class.
+	/// </summary>
+	public interface ITypeDefinitionOrUnknown : IType
+	{
+		/// <summary>
+		/// Gets the full name of this type.
+		/// </summary>
+		FullTypeName FullTypeName { get; }
+	}
+}

ICSharpCode.Decompiler/TypeSystem/Implementation/AbstractType.cs

@@ -91,6 +91,11 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 			return null;
 		}
 
+		public virtual ITypeDefinitionOrUnknown GetDefinitionOrUnknown()
+		{
+			return null;
+		}
+
 		public virtual IEnumerable<IType> DirectBaseTypes {
 			get { return EmptyList<IType>.Instance; }
 		}

ICSharpCode.Decompiler/TypeSystem/Implementation/AbstractTypeParameter.cs

@@ -270,6 +270,11 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 			return null;
 		}
 
+		ITypeDefinitionOrUnknown IType.GetDefinitionOrUnknown()
+		{
+			return null;
+		}
+
 		public IType AcceptVisitor(TypeVisitor visitor)
 		{
 			return visitor.VisitTypeParameter(this);

ICSharpCode.Decompiler/TypeSystem/Implementation/DecoratedType.cs

@@ -59,6 +59,11 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 			return baseType.GetDefinition();
 		}
 
+		ITypeDefinitionOrUnknown IType.GetDefinitionOrUnknown()
+		{
+			return baseType.GetDefinitionOrUnknown();
+		}
+
 		IEnumerable<IEvent> IType.GetEvents(Predicate<IEvent> filter, GetMemberOptions options)
 		{
 			return baseType.GetEvents(filter, options);

ICSharpCode.Decompiler/TypeSystem/Implementation/MetadataTypeDefinition.cs

@@ -530,6 +530,7 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 		public string Namespace => fullTypeName.TopLevelTypeName.Namespace;
 
 		ITypeDefinition IType.GetDefinition() => this;
+		ITypeDefinitionOrUnknown IType.GetDefinitionOrUnknown() => this;
 		TypeParameterSubstitution IType.GetSubstitution() => TypeParameterSubstitution.Identity;
 
 		public IType AcceptVisitor(TypeVisitor visitor)

ICSharpCode.Decompiler/TypeSystem/Implementation/MinimalCorlib.cs

@@ -310,6 +310,7 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 			bool ITypeDefinition.IsRecord => false;
 
 			ITypeDefinition IType.GetDefinition() => this;
+			ITypeDefinitionOrUnknown IType.GetDefinitionOrUnknown() => this;
 			TypeParameterSubstitution IType.GetSubstitution() => TypeParameterSubstitution.Identity;
 
 			IType IType.AcceptVisitor(TypeVisitor visitor)

ICSharpCode.Decompiler/TypeSystem/Implementation/UnknownType.cs

@@ -26,7 +26,7 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 	/// An unknown type where (part) of the name is known.
 	/// </summary>
 	[Serializable]
-	public class UnknownType : AbstractType, ITypeReference
+	public class UnknownType : AbstractType, ITypeDefinitionOrUnknown, ITypeReference
 	{
 		readonly bool namespaceKnown;
 		readonly FullTypeName fullTypeName;
@@ -78,6 +78,11 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 			return this;
 		}
 
+		public override ITypeDefinitionOrUnknown GetDefinitionOrUnknown()
+		{
+			return this;
+		}
+
 		public override string Name {
 			get { return fullTypeName.Name; }
 		}

ICSharpCode.Decompiler/TypeSystem/ModifiedType.cs

@@ -58,6 +58,11 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 			return elementType.GetDefinition();
 		}
 
+		public override ITypeDefinitionOrUnknown GetDefinitionOrUnknown()
+		{
+			return elementType.GetDefinitionOrUnknown();
+		}
+
 		public override IEnumerable<IMethod> GetAccessors(Predicate<IMethod> filter = null, GetMemberOptions options = GetMemberOptions.None)
 		{
 			return elementType.GetAccessors(filter, options);

ICSharpCode.Decompiler/TypeSystem/ParameterizedType.cs

@@ -180,6 +180,11 @@ namespace ICSharpCode.Decompiler.TypeSystem
 			return genericType.GetDefinition();
 		}
 
+		public ITypeDefinitionOrUnknown GetDefinitionOrUnknown()
+		{
+			return genericType.GetDefinitionOrUnknown();
+		}
+
 		/// <summary>
 		/// Gets a type visitor that performs the substitution of class type parameters with the type arguments
 		/// of this parameterized type.

ICSharpCode.Decompiler/TypeSystem/TupleType.cs

@@ -312,6 +312,11 @@ namespace ICSharpCode.Decompiler.TypeSystem
 			return UnderlyingType.GetDefinition();
 		}
 
+		public override ITypeDefinitionOrUnknown GetDefinitionOrUnknown()
+		{
+			return UnderlyingType.GetDefinitionOrUnknown();
+		}
+
 		public override IEnumerable<IEvent> GetEvents(Predicate<IEvent> filter = null, GetMemberOptions options = GetMemberOptions.None)
 		{
 			return UnderlyingType.GetEvents(filter, options);