var (
			mustSelect   []module.Version
			inMustSelect = map[module.Version]bool{}
		)
		for _, pkg := range pkgs {
			if r := modload.PackageModule(pkg); r.Version != "" && !inMustSelect[r] {
				// r has a known version, so force that version.
				mustSelect = append(mustSelect, r)
				inMustSelect[r] = true
			}
		}
		gover.ModSort(mustSelect) // ensure determinism
		mustSelectFor[m] = mustSelect