Creates a unit that implements an interface using bindings in the enclosing environment. The generated unit is essentially the same as
(define id expr) )
for each id that must be defined to satisfy the exports, and each corresponding expr produces the value of id in the environment of the unit-from-context expression. (The unit cannot be written as above, however, since each id definition within the unit shadows the binding outside the unit form.)
See unit for the grammar of tagged-sig-spec.
(define-unit-from-context id tagged-sig-spec)