Hint Rewrite canon3 using check_nonlocal : canon.
Hint Rewrite canon3b using check_nonlocal : canon.
Hint Rewrite canon7 using check_nonlocal : canon.
Hint Rewrite <- (@sepcon_assoc (environ->mpred) _) : canon.

Lemma canon5: forall Q R S,
nonlocal Q ->
Q && (local R && S) = local R && (Q && S).