In article , Nick Maclaren
writes

If anyone has DEFINITE and RELIABLE evidence that Solanum nigrum
has edible berries, I should be interested to hear.

John Akeroyd, writing in his Encyclopedia of Wild Flowers, says of Black
Nightshade - Solanum nigrum:

"NOTE THAT THE berries, ripening from green to black in late summer to
early autumn, are poisonous, like those of its cultivated relative, the
potato, with which it often grows. The leaves, too, contain variable
amounts of poisonous substances, but in Southern Europe they can be seen
being sold, cooked and eaten as a green vegetable similar to spinach.

Other annual nightshades, mostly introduced from South America and all
poisonous, with black, red or green berries, turn up from time to time
as weeds of cultivated or waste ground. The most widespread of them is
Leafy-fruited Nightshade (Solanum sarrachoides) which has green or black
berries partially covered by a swollen, persistent calyx."

J.A. also states that the black berries of Woody Nightshade (Solanum
dulcamara) are poisonous, as are the black berries of Deadly Nightshade
(Atropa belladonna), though they have a long history of medicinal use.

The moral is don't eat wild or cultivated red or black berries unless
their edibility has been ascertained.
--
Alan & Joan Gould, North Lincs.