Additions are conjoined to the corresponding superclass declarations. All other aspects of the declarations are coalesced as one. Variants with and without opt qualifiers on one or more arguments are similarly treated as overloaded. The first two cases are instances of adding features to existing slots. The following additions are permitted.
Analogous rules apply when merging the declarations of two or more superclasses.
Adding a concrete definition to an existing slot. Adding a new clause to an existing effect. Adding a nonconflicting inv constraint. Adding a nonconflicting init constraint. Adding a constraint to a functional slot.