fact: Definition ilist2_hd' {n} {As : Vector.t A (S n)} (il : ilist2 As) : B (Vector.hd As) := Vector.caseS (fun n As => ilist2 As -> B (Vector.hd As)) (fun a As m => ilist2_hd) As il.
imports: Coq.Lists.List Coq.Strings.String Coq.Arith.Arith Fiat.Common.ilist Fiat.Common Fiat.Common.VectorFacts