Restore variants label

source/LookupEngine.Abstractions/Decomposition/Containers/Variants{T}.cs

@@ -81,14 +81,4 @@ IEnumerator<Variant> IEnumerable<Variant>.GetEnumerator()
     {
         return _items.GetEnumerator();
     }
-
-    public object GetResult()
-    {
-        return this;
-    }
-
-    public string? GetMetadata()
-    {
-        return null;
-    }
 }

source/LookupEngine.Abstractions/Decomposition/IVariantsCollection.cs

@@ -0,0 +1,6 @@
+namespace LookupEngine.Abstractions.Decomposition;
+
+public interface IVariantsCollection
+{
+    IVariant Consume();
+}

source/LookupEngine.Abstractions/Decomposition/IVariantsCollection{T}.cs

@@ -1,8 +1,7 @@
 namespace LookupEngine.Abstractions.Decomposition;
 
-public interface IVariantsCollection<in T>
+public interface IVariantsCollection<in T> : IVariantsCollection
 {
     IVariantsCollection<T> Add(T? result);
     IVariantsCollection<T> Add(T? result, string description);
-    IVariant Consume();
 }

source/LookupEngine/Engine/LookupComposer.Features.Redirection.cs

@@ -49,9 +49,16 @@ private object RedirectValue(object value, out Descriptor valueDescriptor)
     private protected virtual object RedirectValue(object value, string target, out Descriptor valueDescriptor)
     {
         var variant = value as IVariant;
-        if (variant is not null)
+        switch (variant)
         {
-            value = variant.Value ?? throw new EngineException("Nullable variant must be handled before decomposition");
+            case null:
+                break;
+            case IVariantsCollection:
+                value = variant;
+                break;
+            default:
+                value = variant.Value ?? throw new EngineException("Nullable variant must be handled before decomposition");
+                break;
         }
 
         valueDescriptor = _options.TypeResolver.Invoke(value, null);

source/LookupEngine/Engine/LookupComposer{T}.Features.Redirection.cs

@@ -63,9 +63,16 @@ private protected override object RedirectValue(object value)
     private protected override object RedirectValue(object value, string target, out Descriptor valueDescriptor)
     {
         var variant = value as IVariant;
-        if (variant is not null)
+        switch (variant)
         {
-            value = variant.Value ?? throw new EngineException("Nullable variant must be handled before decomposition");
+            case null:
+                break;
+            case IVariantsCollection:
+                value = variant;
+                break;
+            default:
+                value = variant.Value ?? throw new EngineException("Nullable variant must be handled before decomposition");
+                break;
         }
 
         valueDescriptor = _options.TypeResolver.Invoke(value, null);