During LWG review of P3481R3 it was noted that we need to say "except that `sndr` is only evaluated once" because it's used in get-domain-early(sndr), but that exposition-only-function doesn't actually use its argument, it only cares about the type, and it default constructs a `Domain` of a type determined by using the type of `sndr`.

If we had something like:

template<class Sender>
using get-domain-early-t = decltype(get-domain-early(declval<const Sender&>()));

then we wouldn't need to use `sndr` twice in expressions that currently use get-domain-early(sndr).