Initial feedback on the review was generally positive on the concept, but several reviewers were troubled by the potential for source incompatibilities. The proposal author investigated options for maintaining compatibility better, and when they seemed to work out, the core team elected to amend the proposal during review. The community then expressed strong support for the revised proposal, and the feeling among reviewers was that there was no need for a second review. The core team discussed this and agreed. Accordingly, the revised proposal is accepted with modifications.
The schedule for this proposal and review was compressed quite a bit in order to try to meet the deadline for Swift 5.3. I'd like to thank the community for its patience and forbearance with this sort of unusual process.
As always, thank you for helping to make Swift a better language.