>     suggest either making promises a disjoint type or making them
>     indistinguishable from ordinary values, which would mean implicit
>     forcing and probably a Haskell-like kernel for Scheme.
>
> IMO the second option would be extremely destructive to the Scheme
> effort: all existing Schemes would have to be not just modified but
> discarded. The first option is feasible and indeed desirable.

+1 to a reliable `promise?` predicate.

Implicit forcing makes it harder to reason about efficiency. That goes
against one of the core values of Scheme. (IMHO one of the most
important values.)