in src/main/scala/org/intellij/scala/bundle/Descriptor.scala [12:16]
def |(other: Descriptor): Descriptor = {
case component if descriptor.isDefinedAt(component) && other.isDefinedAt(component) => descriptor(component) | other(component)
case component if descriptor.isDefinedAt(component) => descriptor(component)
case component if other.isDefinedAt(component) => other(component)
}