Definition lseg_cons_right (ls: listspec list_structid list_link list_token)
dsh psh (l: list val) (x z: val) : mpred :=
!! (~ ptr_eq x z) &&
EX r:list val , EX y:val,
!!(l=r++y::nil /\ is_pointer_or_null y)  &&
list_cell ls dsh (vund ls) y *
field_at psh list_struct (StructField list_link :: nil) (valinject (nested_field_type list_struct (StructField list_link :: nil)) z) y *
lseg ls dsh psh r x y.

Lemma lseg_unroll_right (ls: listspec list_structid list_link list_token): forall sh sh' l x z ,
lseg ls sh sh' l x z = (!! (ptr_eq x z) && !! (l=nil) && emp) || lseg_cons_right ls sh sh' l x z.