Common Chokecherry, "Prunus virginiana" can be toxic to animals and humans due to the cyanide the leaves, twigs, and seeds can contain. However, composting of the leaves, and twigs is a very good use of them and apparently does not result in cyanid poisoning of people that eat food grown in soils where that compost has been used.
I have been composting leaves from the Common Chokecherry for many years as well as using the chipped wood for mulches and have not seen the levels of cyanide in my soil increase in that time, nor have I seen the levels of Arsenic (another poison that does accumulate in plants) increase.
Since the cyanide is more readily available in wilted leaves it probably would not be a good idea to eat very many of them, or feed them to animals.

Any cyanide that is released during composting dissipates or is consumed by the compost microbes.

Thank you! I wanted to make sure that the leaves would be safe for composting before I purchased 2 more trees and this definitely helps.