Added check for "unspeakable" types.

- https://stackoverflow.com/a/9256695/10340424

src/ExtendedXmlSerializer/ContentModel/Reflection/AssemblyTypePartitions.cs

@@ -23,7 +23,8 @@ public AssemblyTypePartitions(IPartitionedTypeSpecification specification, IType
 			: this(specification, formatter.Get) {}
 
 		public AssemblyTypePartitions(ISpecification<TypeInfo> specification, Func<TypeInfo, string> formatter)
-			: this(specification.IsSatisfiedBy, formatter, ApplicationTypes, x => x.Namespace) {}
+			: this(specification.And(ApplicationTypeSpecification.Default).IsSatisfiedBy, formatter, ApplicationTypes,
+			       x => x.Namespace) {}
 
 		// ReSharper disable once TooManyDependencies
 		public AssemblyTypePartitions(Func<TypeInfo, bool> specification, Func<TypeInfo, string> formatter,

src/ExtendedXmlSerializer/ContentModel/Reflection/GenericTypes.cs

@@ -1,10 +1,10 @@
-using System.Collections.Immutable;
-using System.Reflection;
 using ExtendedXmlSerializer.ContentModel.Identification;
 using ExtendedXmlSerializer.Core.Sources;
 using ExtendedXmlSerializer.Core.Specifications;
 using ExtendedXmlSerializer.ReflectionModel;
 using JetBrains.Annotations;
+using System.Collections.Immutable;
+using System.Reflection;
 
 namespace ExtendedXmlSerializer.ContentModel.Reflection
 {

src/ExtendedXmlSerializer/ReflectionModel/ApplicationTypeSpecification.cs

@@ -1,13 +1,14 @@
+using ExtendedXmlSerializer.Core.Specifications;
 using System.Reflection;
 using System.Runtime.CompilerServices;
-using ExtendedXmlSerializer.Core.Specifications;
 
 namespace ExtendedXmlSerializer.ReflectionModel
 {
-	class ApplicationTypeSpecification : InverseSpecification<TypeInfo>
+	sealed class ApplicationTypeSpecification : InverseSpecification<TypeInfo>
 	{
 		public static ApplicationTypeSpecification Default { get; } = new ApplicationTypeSpecification();
 
-		ApplicationTypeSpecification() : base(IsDefinedSpecification<CompilerGeneratedAttribute>.Default) {}
+		ApplicationTypeSpecification()
+			: base(IsDefinedSpecification<CompilerGeneratedAttribute>.Default.Or(IsUnspeakable.Default)) {}
 	}
 }

src/ExtendedXmlSerializer/ReflectionModel/IsUnspeakable.cs

@@ -0,0 +1,15 @@
+using ExtendedXmlSerializer.Core.Specifications;
+using System.Reflection;
+
+namespace ExtendedXmlSerializer.ReflectionModel
+{
+	/// <summary>
+	/// Reference: https://stackoverflow.com/a/9256695/10340424
+	/// </summary>
+	sealed class IsUnspeakable : DelegatedSpecification<TypeInfo>
+	{
+		public static IsUnspeakable Default { get; } = new IsUnspeakable();
+
+		IsUnspeakable() : base(x => x.Name.StartsWith("<")) {}
+	}
+}

test/ExtendedXmlSerializer.Tests.ReportedIssues/Issue470Tests.cs

@@ -0,0 +1,34 @@
+using ExtendedXmlSerializer.Configuration;
+using ExtendedXmlSerializer.Tests.ReportedIssues.Support;
+using FluentAssertions;
+using JetBrains.Annotations;
+using System;
+using System.Threading.Tasks;
+using Xunit;
+
+namespace ExtendedXmlSerializer.Tests.ReportedIssues
+{
+	public sealed class Issue470Tests
+	{
+		[Fact]
+		public void Verify()
+		{
+			var instance = new Foo();
+			new ConfigurationContainer().Create().ForTesting().Cycle(instance).Should().BeEquivalentTo(instance);
+		}
+
+		public class Foo
+		{
+			public string Bar { get; set; }
+		}
+
+		public class Something
+		{
+			[UsedImplicitly]
+			Func<object, Task> Check<T>(Func<T, Task> data)
+			{
+				return async o => await data((T)o); // this causes it to bomb out
+			}
+		}
+	}
+}