in lib/src/version.dart [37:44]
static int prioritize(Version a, Version b) {
// Sort all prerelease versions after all normal versions. This way
// the solver will prefer stable packages over unstable ones.
if (a.isPreRelease && !b.isPreRelease) return -1;
if (!a.isPreRelease && b.isPreRelease) return 1;
return a.compareTo(b);
}