Remove sealed and make protected the TypeInspectors

Fixes #984

YamlDotNet/Serialization/TypeInspectors/CachedTypeInspector.cs

@@ -30,7 +30,7 @@ namespace YamlDotNet.Serialization.TypeInspectors
     /// <summary>
     /// Wraps another <see cref="ITypeInspector"/> and applies caching.
     /// </summary>
-    public sealed class CachedTypeInspector : TypeInspectorSkeleton
+    public class CachedTypeInspector : TypeInspectorSkeleton
     {
         private readonly ITypeInspector innerTypeDescriptor;
         private readonly ConcurrentDictionary<Type, List<IPropertyDescriptor>> cache = new ConcurrentDictionary<Type, List<IPropertyDescriptor>>();

YamlDotNet/Serialization/TypeInspectors/CompositeTypeInspector.cs

@@ -28,7 +28,7 @@ namespace YamlDotNet.Serialization.TypeInspectors
     /// <summary>
     /// Aggregates the results from multiple <see cref="ITypeInspector" /> into a single one.
     /// </summary>
-    public sealed class CompositeTypeInspector : TypeInspectorSkeleton
+    public class CompositeTypeInspector : TypeInspectorSkeleton
     {
         private readonly IEnumerable<ITypeInspector> typeInspectors;
 

YamlDotNet/Serialization/TypeInspectors/NamingConventionTypeInspector.cs

@@ -29,7 +29,7 @@ namespace YamlDotNet.Serialization.TypeInspectors
     /// Wraps another <see cref="ITypeInspector"/> and applies a
     /// naming convention to the names of the properties.
     /// </summary>
-    public sealed class NamingConventionTypeInspector : TypeInspectorSkeleton
+    public class NamingConventionTypeInspector : TypeInspectorSkeleton
     {
         private readonly ITypeInspector innerTypeDescriptor;
         private readonly INamingConvention namingConvention;

YamlDotNet/Serialization/TypeInspectors/ReadableAndWritablePropertiesTypeInspector.cs

@@ -28,7 +28,7 @@ namespace YamlDotNet.Serialization.TypeInspectors
     /// <summary>
     /// Returns the properties of a type that are both readable and writable.
     /// </summary>
-    public sealed class ReadableAndWritablePropertiesTypeInspector : TypeInspectorSkeleton
+    public class ReadableAndWritablePropertiesTypeInspector : TypeInspectorSkeleton
     {
         private readonly ITypeInspector innerTypeDescriptor;
 

YamlDotNet/Serialization/TypeInspectors/ReadableFieldsTypeInspector.cs

@@ -30,7 +30,7 @@ namespace YamlDotNet.Serialization.TypeInspectors
     /// <summary>
     /// Returns the properties and fields of a type that are readable.
     /// </summary>
-    public sealed class ReadableFieldsTypeInspector : ReflectionTypeInspector
+    public class ReadableFieldsTypeInspector : ReflectionTypeInspector
     {
         private readonly ITypeResolver typeResolver;
 
@@ -46,7 +46,7 @@ public override IEnumerable<IPropertyDescriptor> GetProperties(Type type, object
                 .Select(p => (IPropertyDescriptor)new ReflectionFieldDescriptor(p, typeResolver));
         }
 
-        private sealed class ReflectionFieldDescriptor : IPropertyDescriptor
+        protected class ReflectionFieldDescriptor : IPropertyDescriptor
         {
             private readonly FieldInfo fieldInfo;
             private readonly ITypeResolver typeResolver;

YamlDotNet/Serialization/TypeInspectors/ReadablePropertiesTypeInspector.cs

@@ -30,7 +30,7 @@ namespace YamlDotNet.Serialization.TypeInspectors
     /// <summary>
     /// Returns the properties of a type that are readable.
     /// </summary>
-    public sealed class ReadablePropertiesTypeInspector : ReflectionTypeInspector
+    public class ReadablePropertiesTypeInspector : ReflectionTypeInspector
     {
         private readonly ITypeResolver typeResolver;
         private readonly bool includeNonPublicProperties;
@@ -60,7 +60,7 @@ public override IEnumerable<IPropertyDescriptor> GetProperties(Type type, object
                 .Select(p => (IPropertyDescriptor)new ReflectionPropertyDescriptor(p, typeResolver));
         }
 
-        private sealed class ReflectionPropertyDescriptor : IPropertyDescriptor
+        protected class ReflectionPropertyDescriptor : IPropertyDescriptor
         {
             private readonly PropertyInfo propertyInfo;
             private readonly ITypeResolver typeResolver;

YamlDotNet/Serialization/TypeInspectors/WritablePropertiesTypeInspector.cs

@@ -30,7 +30,7 @@ namespace YamlDotNet.Serialization.TypeInspectors
     /// <summary>
     /// Returns the properties of a type that are writable.
     /// </summary>
-    public sealed class WritablePropertiesTypeInspector : ReflectionTypeInspector
+    public class WritablePropertiesTypeInspector : ReflectionTypeInspector
     {
         private readonly ITypeResolver typeResolver;
         private readonly bool includeNonPublicProperties;
@@ -61,7 +61,7 @@ public override IEnumerable<IPropertyDescriptor> GetProperties(Type type, object
                 .ToArray();
         }
 
-        private sealed class ReflectionPropertyDescriptor : IPropertyDescriptor
+        protected class ReflectionPropertyDescriptor : IPropertyDescriptor
         {
             private readonly PropertyInfo propertyInfo;
             private readonly ITypeResolver typeResolver;