feat(widget/basic): use has_coe_t (#544)
feat(widget/basic): use has_coe_t (#544)

See https://leanprover.zulipchat.com/#narrow/stream/113488-general/topic/pi.2Enat_apply

@EdAyers do you see any problem with this change?



digama0/lean,leanprover-community/lean,leanprover-community/lean,leanprover-community/lean,leanprover-community/lean,leanprover-community/lean,digama0/lean,leanprover-community/lean,digama0/lean,digama0/lean,digama0/lean,digama0/lean