パッチバージョン(1.2.0 => 1.2.1)でビルドできるSwiftバージョンが落とされるの使ってるほうはちょっとびっくりするな。

The package now has a minimum Swift version of Swift 5.7. (#240)

https://github.com/apple/swift-algorithms/releases/tag/1.2.1 (edited)

Release Swift Algorithms 1.2.1 · apple/swift-algorithms

Changes The package now has a minimum Swift version of Swift 5.7. (#240) Adds a project for building with Xcode. (#246) Fixes Fix for Swift 6 language mode errors. (#230) Minor improvements to d...