Section dup.
Definition duplicable P := P |-- |==> P * P.
Hint Resolve emp_duplicable : dup.
Hint Resolve sepcon_duplicable : dup.
Hint Resolve invariant_duplicable' : dup.
Hint Resolve ghost_snap_duplicable : dup.

Lemma prop_duplicable : forall P Q, duplicable Q -> duplicable (!!P && Q).