Hint Rewrite
@field_at_data_at_cancel'
@field_at_data_at
@field_at__data_at_
@data_at__data_at : cancel.
(* END new experiments *)

Lemma data_at__Tarray:
forall {CS: compspecs} sh t n a,
data_at_ sh (Tarray t n a) =
data_at sh (Tarray t n a) (list_repeat (Z.to_nat n) (default_val t)).