An example demonstrating the "incoherent instances" problem in Swift
While the language tries hard to prevent it, it is possible to have two conformances of the same type to the same protocol
in the same Swift program. This sample demonstrates the problem by showing how two values of the same SortedArray<T: Comparable>
type can end up using different T: Comparable conformances. You can find some discussion on Twitter: https://twitter.com/anandabits/status/979677851405385731
The existence of this problem leads to the common advice to only provide protocol conformances in a module that declares either the type or the protocol.
Ed Kmett discussed this problem as it exists in Haskell in his talk Type Classes vs the World
NOTE: The code contained in this repo was written a couple of years ago. It appears to have a linker error now and I don't have time to figure out what the problem is, but was executable at the time it was written.