mathlib3

272e2d22 - feat(data/{int, nat, rat}/cast): extensionality lemmas (#6788)

feat(data/{int, nat, rat}/cast): extensionality lemmas (#6788) Extensionality lemmas Co-authored-by: Eric Wieser <wieser.eric@gmail.com> Co-authored-by: Benjamin Davidson <68528197+benjamindavidson@users.noreply.github.com>