it prevents genericThing to provide an instance of Thing[F] if an implicit one is already
available elsewhere. This effectively gives genericThing a lower priority than the already
existing implicits - without having to deal with cumbersome priority scoping.
Evidence that no implicit instance of the same type as the one being currently searched is available elsewhere.
Added to an implicit def like
it prevents
genericThing
to provide an instance ofThing[F]
if an implicit one is already available elsewhere. This effectively givesgenericThing
a lower priority than the already existing implicits - without having to deal with cumbersome priority scoping.