2nd priority implicit BuilderArrMap instances evidence for Any and RArr. This is the fallback builder implicit for Arrs that do not have their own specialist Arr classes. It is placed in this low priority trait to give those specialist Arr classes implicit priority. The notA implicit parameter is to exclude user defined types that have their own specialist Arr classes.
2nd priority implicit BuilderArrMap instances evidence for Any and RArr. This is the fallback builder implicit for Arrs that do not have their own specialist Arr classes. It is placed in this low priority trait to give those specialist Arr classes implicit priority. The notA implicit parameter is to exclude user defined types that have their own specialist Arr classes.