Modules
Predicates that classify a unification problem into one of the decidable
fragments handled by ShotUn.Pattern (Miller patterns) and
ShotUn.Matching (Huet second-order matching), plus a helper for
computing the order of a simple type.
Decidable higher-order matching for the second-order fragment.
Higher-order pattern unification (Miller 1991).
Represents a single solution to a unification problem.