rintro rfl
case mpr
ι : Type u_1
inst✝¹ : IndexType ι
inst✝ : LawfulIndexType ι
x y : Fin (card ι)
⊢ x = y → fromFin x = fromFin y
case mpr
ι : Type u_1
inst✝¹ : IndexType ι
inst✝ : LawfulIndexType ι
x : Fin (card ι)
⊢ fromFin x = fromFin x