Goal:
    A : Type  P : A → A → Type  l : list A  tl : list A  tl' : list A
  ============================
   (OnOne2 P tl tl' → OnOne2 P (l ++ tl) (l ++ tl'))


DEBUG:Going to execute:
induction l

Goals:
    A : Type  P : A → A → Type  tl : list A  tl' : list A
  ============================
   (OnOne2 P tl tl' → OnOne2 P ([] ++ tl) ([] ++ tl'))

  
  A : Type
  P : A → A → Type
  a : A
  l : list A
  tl : list A
  tl' : list A
  IHl : OnOne2 P tl tl' → OnOne2 P (l ++ tl) (l ++ tl')
  ============================
   (OnOne2 P tl tl' → OnOne2 P ((a :: l) ++ tl) ((a :: l) ++ tl'))


DEBUG:Going to execute:
simpl
DEBUG LTAC Evaluated term: l

Goals:
    A : Type  P : A → A → Type  tl : list A  tl' : list A
  ============================
   (OnOne2 P tl tl' → OnOne2 P tl tl')

  
  A : Type
  P : A → A → Type
  a : A
  l : list A
  tl : list A
  tl' : list A
  IHl : OnOne2 P tl tl' → OnOne2 P (l ++ tl) (l ++ tl')
  ============================
   (OnOne2 P tl tl' → OnOne2 P (a :: l ++ tl) (a :: l ++ tl'))


DEBUG:Going to execute:
try constructor