one_member.m:046: Error: this `arbitrary' scope is not nested inside a
one_member.m:046:   `promise_equivalent_solution_sets' scope.
one_member.m:049: In `one_member2'(in, out):
one_member.m:049:   warning: determinism declaration could be tighter.
one_member.m:049:   Declared `nondet', inferred `semidet'.
one_member.m:053: Error: the `arbitrary' goal lists an extra variable: Tree.
one_member.m:053: Error: this `arbitrary' scope and the
one_member.m:053:   `promise_equivalent_solution_sets' scope it is nested
one_member.m:053:   inside overlap on the variable Item.
one_member.m:052:   This is the outer `promise_equivalent_solution_sets' scope.
one_member.m:054: Error: unification for non-canonical type
one_member.m:054:   `one_member.set_ctree234'/1 occurs in a context which
one_member.m:054:   requires all solutions.
one_member.m:054:   Since the type has a user-defined equality predicate, I
one_member.m:054:   must presume that there is more than one possible concrete
one_member.m:054:   representation for each abstract value of this type. The
one_member.m:054:   results of this unification might depend on the choice of
one_member.m:054:   concrete representation. Finding all possible solutions to
one_member.m:054:   this unification would require backtracking over all
one_member.m:054:   possible representations, but I am not going to do that
one_member.m:054:   implicitly. (If that is really what you want, you must do
one_member.m:054:   it explicitly.)
one_member.m:055:   Call to do_one_member can fail.
one_member.m:063: Error: `promise_equivalent_solution_sets' scope is nested
one_member.m:063:   inside another.
one_member.m:062:   This is the outer `promise_equivalent_solution_sets' scope.