open nat structure foo [class] := (a : nat) (b : nat) definition i1 [instance] [priority default+1] : foo := foo.mk 1 1 definition i2 [instance] : foo := foo.mk 2 2 example : foo.a = 1 := rfl definition i3 [instance] [priority default+2] : foo := foo.mk 3 3 example : foo.a = 3 := rfl