First you ask how the hell someone could come up with this construction.
Then you realize it was this guy: https://en.wikipedia.org/wiki/Erik_Demaine
replies(5):
Then you realize it was this guy: https://en.wikipedia.org/wiki/Erik_Demaine
I understand the idea behind that phrasing but I'm not sure I agree with it. Are you no longer a child prodigy once you turn 18? I don't think I'd ever say "former intelligent child".. Would I?
Maybe "a child prodigy in his youth" would be both precise and succinct enough, but at the same time language is for humans and I feel humans know what is meant by former child prodigy.