(** Invariance by assignment to an irrelevant temporary *)

Lemma match_envs_change_temp:
forall f cenv e le m lo hi te tle tlo thi id v,
match_envs f cenv e le m lo hi te tle tlo thi ->
le!id = None -> VSet.mem id cenv = false ->
match_envs f cenv e le m lo hi te (PTree.set id v tle) tlo thi.