Ltac try_conjuncts_solver :=
    lazymatch goal with H:_ |- ?A =>
         no_evars A;
         clear H; try immediate; auto; prove_it_now; fail
    end.Ltac try_conjuncts :=
 first [ simple eapply conj;
                [try_conjuncts_solver | try_conjuncts ]
        | simple eapply try_conjuncts_lem2;
                [try_conjuncts_solver | match goal with H:_ |- _ => apply H end ]
        | simple eapply try_conjuncts_lem;
            [intro; try_conjuncts | intro; try_conjuncts
            |match goal with H:_ |- _ => apply H end ]
        | match goal with H:_ |- _ => instantiate (1:=True) in H;
                try_conjuncts_solver
          end
        | match goal with H:_ |- _ => apply H end
        ].Ltac prop_right_cautious :=
 try solve [simple apply prop_right; auto; prove_it_now].Ltac prune_conjuncts :=
 repeat rewrite and_assoc';
 first [simple eapply try_conjuncts_prop;
              [intro; try_conjuncts
              | cbv beta; repeat rewrite and_True; prop_right_cautious ]
         | simple eapply try_conjuncts_prop_and;
              [intro; try_conjuncts
              | cbv beta; repeat rewrite and_True; try simple apply go_lower_lem1]
         | idtac].Ltac entailer' :=
 repeat (progress (ent_iter; normalize));
 try simple apply prop_and_same_derives;
 prune_conjuncts;
 try rewrite (prop_true_andp True) by apply Coq.Init.Logic.I;
 try solve_valid_pointer;
 try first [apply derives_refl
              | simple apply FF_left
              | simple apply TT_right].

Lemma empTrue: @derives mpred Nveric (@emp mpred Nveric Sveric) (@prop mpred Nveric True).