Definition dirr1 (B : {set gT}) : dIirr B := (false, 0).
Definition ndirr (B : {set gT}) (i : dIirr B) : dIirr B :=
(~~ i.1, i.2).

Lemma dirr_dIirrPE J (f : J -> 'CF(G)) (P : pred J) :
(forall j, P j -> f j \in dirr G) ->
forall j, P j -> dchi (dirr_dIirr f j) = f j.