blame していったら経緯がありました．prerelease バージョンをフェッチするかどうかは opt-in になっていて，バージョン制約に prerelease が現れたら初めてフェッチする対象に含まれるんですね． https://github.com/apple/swift-package-manager/issues/4996 https://github.com/apple/swift/issues/43651 (edited)

[SR-5192] swiftpm 4 incorrectly resolves prerelease major version a...

Previous ID SR-5192 Radar None Original Reporter @sharplet Type Bug Status Resolved Resolution Duplicate Environment % swift --version Apple Swift version 4.0 (swiftlang-900.0.43 clang-900.0.22.8) ...

[SR-1039] Fetch a dependency with a specified Pre-release version ·...

Previous ID SR-1039 Radar rdar://problem/31214600 Original Reporter kkoval (JIRA User) Type Bug Status Resolved Resolution Done Additional Detail from JIRA Votes 0 Component/s Package Manager Label...