Hey everyone, thank you all for the helpful comments! These definitely aren't blueberries--they are quite firm despite the dark purple color and they do not have the same type of indent on the end as most blueberries (where the flower used to be). I was thinking it might be either a prunus or some kind of a serviceberry--but just wanted to make sure this wasn't something like a (poisonous) buckthorn.... Later this afternoon I'll cut one of the berries open to see what is inside, and maybe that will help narrow things down. The color in the picture is fairly accurate--fruit are dark purple, leaves are dark green with red/purple. This is some sort of an ornamental bush, too--someone planted it intentionally for looks, judging by the rest of the yard and the bush itself.

Foliage and canes similar to Thornless Boysen berry.

Definitely Lawson Cypress. However, does not look like either the true 'Golden King' of Europe in the 1950s or the 'Golden Showers' that Monrovia misapplied the same name to subsequently.

Nope, please do not eat them. This part of a quite a group of similar short lived perennial vining Solanums commonly called nightshades, which like potatoes for example has almost all parts poisonous. Some Solanums like the tomato and eggplant have edible or mostly edible fruits but volunteers of the black group are difficult to separate the good from the bad. They can be handled as in pulling them as weeds. One common edible of this group grown for its fruits is the garden huckleberry, which I have never grown, but if someone around you has, you may have volunteers since they set a lot of seed and escapes are common just like they are for the related Chinese lantern plant. In regard to the whole nightshade group, if you do not know exactly what you have don't eat it. Toxicity varies dramatically across the fruits, and the green stems and leaves are almost always toxic to some degree.