[swift-evolution] Proposal: An Either Type in the STL

[Guillaume Lessard]

There is probably a greater need for a non-agnostic Result monad type (with descriptive cases .Value and .Error) for manual error propagation. If it’s not agnostic then the happy and unhappy paths can be better optimized.

Such a type was proposed but not designed in <https://github.com/apple/swift/blob/master/docs/ErrorHandling.rst#manual-propagation-and-manipulation-of-errors>. Was it abandoned or simply left for later?
(There are several implementations available on github, heh)

Guillaume Lessard