type sourceBridge interface {
	listVersions() ([]Version, error)
}

type Constraint interface {
	copyTo(*ConstraintMsg)
}

type ConstraintMsg struct{}

func (m *ConstraintMsg) asUnpairedVersion() UnpairedVersion {
	return nil
}

type Version interface {
	Constraint
}

type UnpairedVersion interface {
	Version
}

var _ Constraint = UnpairedVersion(nil)

type sourceBridge interface {
	listVersions() ([]Version, error)
}

type Constraint interface {
	copyTo(*ConstraintMsg)
}

type ConstraintMsg struct{}

func (m *ConstraintMsg) asUnpairedVersion() UnpairedVersion {
	return nil
}

type Version interface {
	Constraint
}

type UnpairedVersion interface {
	Version
}

var _ Constraint = UnpairedVersion(nil)