[Pitch] Access-level on import statements

[Douglas_Gregor]

@xymus

Here’s a proposal for more control over dependencies and imports in Swift. With this feature you can mark imports as public (the current regular import), internal for implementation details of the module, and private or fileprivate for implementation details to the source file.

This is a fantastic proposal and I'm thrilled to see it.

As others have noted, making the default access level internal in Swift 6 is a great idea. Can that "Future direction" section move into the proposal itself? Additionally, I'd like for this to get an upcoming feature flag (e.g., InternalImports) so that we can enable this behavior with -enable-upcoming-feature for existing code.

In practice, there are leaks allowing use of extension members from transitive dependencies.

I would love for us to plug these leaks; they're unprincipled and cause problems in practice.

Doug

[xymus (Alexis Laferrière)]

@Douglas_Gregor

Can that "Future direction" section move into the proposal itself?

Yes I'll move it over. The response has been only positive, I expected it to cause more debates.

@Douglas_Gregor

Additionally, I'd like for this to get an upcoming feature flag (e.g., InternalImports) so that we can enable this behavior with -enable-upcoming-feature for existing code.

That makes sense, and it looks like it will clean up the implementation a bit. I'll add it as soon as we have a proposal number to attach to it.

@Douglas_Gregor

I would love for us to plug these leaks; they're unprincipled and cause problems in practice.

The Swift 6 transition is a good opportunity to fix them as the fix may be source breaking.