"private type in exported type signature" error does not check re-exports

[SimonSapin]

… apparently, or it would have caught #19271. It should, especially if libcore and other crates that libstd is a facade of can not be used directly in the stable channel.

That is, if a function, type, or trait is re-exported, all the signatures involved should also be checked for type that are not also reachable from the same crate. Otherwise it is possible to get a value of a type that can not be named, which this error tries to prevent in the first place.

[alexcrichton]

The RFC from which this error originates defines a private type as one not marked pub, not one which is not reachable from the crate root. In this case the variants are all pub, so this error does not apply to them. Closing as working as intended (albeit unfortunately)