ConstThe expressions a capturing call holds on to.
ReadonlyevaluateIn: <Info>(Links every name in expr against environment and hands back what stays unresolved.
The finishing pass over a complete graph: it settles what a call really evaluates, which the call itself
could not know. A capture reaches the eval that forces it, a promise reaches the bindings it may be
forced against, and a masked name the caller binds after all loses its mark.
Every expression the value at id may hold, with the call that captured it. Several is normal.
A language object reads nothing where it is written and everything where it reaches
eval, with the bindings in effect there. Working on the finished graph makes assignments, branches, loops, and calls one traversal.