Remark permutation_norepet:
  forall (A: Type) (l l': list A), Permutation l l' -> list_norepet l -> list_norepet l'.

Lemma build_compilenv_sound: forall f cenv sz, build_compilenv f = (cenv, sz) -> list_norepet (map fst (Csharpminor.fn_vars f)) -> cenv_compat cenv (Csharpminor.fn_vars f) sz /\ cenv_separated cenv (Csharpminor.fn_vars f).