Constrains all elements of a collection to be different from each other. Semantically, all elements of the collection are pairwise different.
This constraint is also known as alldifferent_cst in the global constraints catalog, and is implemented using Gecode's distinct() constraint.
ConsistencyModule is the optional module specification to give the consistency level for the propagation for this constraint: gfd_vc for value consistency (naive), gfd_bc for bounds consistency, and gfd_gac for domain (generalised arc) consistency.