Definition nonlocal (Q: environ->mpred) := True.
Ltac check_nonlocal :=
match goal with
|  |- nonlocal (local _) => fail 1
|  |- nonlocal (prop _) => fail 1
|  |- nonlocal (andp _ _) => fail 1
|  |- nonlocal (sepcon _ _) => fail 1
| |- _ => apply I
end.

Lemma canon7: forall R1 P Q R,
nonlocal `(R1) ->
do_canon `(R1) (PROPx P (LOCALx Q (SEPx R))) = (PROPx P (LOCALx Q (SEPx (R1::R)))).