Instance naming for Equiv instances

Stream: mathlib4

[Arien Malec]

I noted in a port that in Lean 3 an unnamed instance of equiv for fintype was referred to subsequently as equiv.fintype -- is there some deliberabe automagic here, and if so, should I name the instance in the port Equiv.fintype?

[Kevin Buzzard]

That looks like the lean 3 instance naming convention.