Goal:
    A : Type  H : ReflectEq A  l1 : list A  l2 : list A
  ============================
   (let
    '(prefix, l1', l2') := split_prefix l1 l2 in
     l1 = prefix ++ l1' ∧ l2 = prefix ++ l2')


DEBUG:Going to execute:
constr:(fun_elim)
Level 6: Backtrace:


Could not find an instance for "FunctionalElimination 
                                  (split_prefix l1) 
                                  ?fun_elim_ty ?n"
in environment:
A : Type
H : ReflectEq A
l1, l2 : list A