[reflect.synopsis] 21.12.4.2: unpack_sequence_t is a variable template initialized by a type (Needs NB Comment)

[Dani-Hub]

This is not a review deviation of the accepted p0670r4 document but was observed during the review:

In [reflect.synopsis], the template unpack_sequence_t is defined as follows:

template <template <class...> class Tpl, ObjectSequence T>
constexpr auto unpack_sequence_t = unpack_sequence<Tpl, T>::type;

but according to [reflect.ops.objseq] p3:

All specializations of unpack_sequence<Tpl, T> shall meet the TransformationTrait requirements
(23.15.1). The nested type named type is an alias to the template Tpl specialized
with the types in T.

So it seems that what unpack_sequence_t actually defines would be a type alias instead of a variable template and should be corrected to

template <template <class...> class Tpl, ObjectSequence T>
using unpack_sequence_t = typename unpack_sequence<Tpl, T>::type;

[Axel-Naumann]

Resolved, @camio ?