Goal:
  
  b : Byte.byte
  xs : t
  b0 : Byte.byte
  ys : t
  IHxs : forall ys : t,
         eqb xs ys = match compare xs ys with
                     | Eq => true
                     | _ => false
                     end
  ============================
   ((if ByteCompare.eqb b b0 then eqb xs ys else false) =
    match
      match ByteCompare.compare b b0 with
      | Eq => compare xs ys
      | Lt => Lt
      | Gt => Gt
      end
    with
    | Eq => true
    | _ => false
    end)


DEBUG:Going to execute:
trivial; hnf