Something matching the grammar doesn't mean it does what you want it to. All components of an import path except the last are treated as module components at the moment.

I think the only sensible behavior for this would be to introduce RoundingMode into the top-level scope, which would be enough of a new feature to need the Swift Evolution Process.

Comment by aaron crespo (JIRA)

Thanks for commenting @belkadan this was just a minimal example of the import side of it. The usage side also has some quirks.

Similarly:

// ExposesSpecialString Module
public typelias SpecialString = String

public func format(specialString: SpecialString) {}

Has some very different behaviors:

import ExposesSpecialString
// SpecialString is in the name space now
// vs
import typealias ExposesSpecialString.SpecialString
// usually an error

Some open source Libraries under some circumstances support this. I'm not sure if some shadowing or namespace collisions are happening. EX: "import typealias RxSwift.Single".

Usually tho top level type aliases that aren't importable.

I'm not sure what you mean by "usually an error". The latter is supposed to work. If you have a test case where it doesn't, please attach it!