fact: Definition sigT_of_sigT2 (A : Type) (P Q : A -> Type) (X : sigT2 P Q) : sigT P := existT P (let (a, _, _) := X in a) (let (x, p, _) as s return (P (let (a, _, _) := s in a)) := X in p).
imports: Notations Ltac Datatypes Logic