Hint Resolve multipar_context_independent.

Lemma joins_iapp : forall S D a1 a2 L1 L2,
(forall x, x `notin` L1 -> RhoCheck Irrel x (open_tm_wrt_tm a1 (a_Var_f x))) ->
(forall x, x `notin` L2 -> RhoCheck Irrel x (open_tm_wrt_tm a2 (a_Var_f x))) ->
joins S D (open_tm_wrt_tm a1 a_Bullet) (open_tm_wrt_tm a2 a_Bullet) ->
joins S D (a_UAbs Irrel a1) (a_UAbs Irrel a2).