Generics & Reflection - GenericArguments[0] violates the constraint of type

Your code tries to create an instance of DocumentLibraryRepository<IRepository<Document>> instead of DocumentLibraryRepository<Document>.

You want to use this code instead:

var genericArgument = typeof(T).GetGenericArguments().FirstOrDefault();
if (tempType != null && genericArgument != null)
{
    Type newType = tempType.MakeGenericType(genericArgument);