Revert "Remove unused code"

This reverts commit b0efbdf5e8.

src/Shared/SharedTypeExtensions.cs

@@ -63,6 +63,20 @@ namespace System
                && !type.IsInterface
                && (!type.IsGenericType || !type.IsGenericTypeDefinition);
 
+        public static bool IsGrouping(this Type type) => IsGrouping(type.GetTypeInfo());
+
+#if NETCOREAPP3_1
+        private static bool IsGrouping(TypeInfo type)
+            => type.IsGenericType
+               && (type.GetGenericTypeDefinition() == typeof(IGrouping<,>)
+                   || type.GetGenericTypeDefinition() == typeof(SystemInteractiveAsync::System.Linq.IAsyncGrouping<,>));
+#else
+        private static bool IsGrouping(TypeInfo type)
+            => type.IsGenericType
+               && (type.GetGenericTypeDefinition() == typeof(IGrouping<,>)
+                   || type.GetGenericTypeDefinition() == typeof(IAsyncGrouping<,>));
+#endif
+
         public static Type UnwrapEnumType(this Type type)
         {
             var isNullable = type.IsNullableType();