JetBrains tooling does use schema metadata for it's autocompletion. I'm not sure though if it's anywhere close to full-on Haskell autocompletion in the Atom editor (very fiddly and prone to break on minor version changes, I must say).
Offtopic, but I am genuinely curious now about whether Atom's Haskell autocompletion is significantly better than in other editors like VSCode, or (n)vim with things like YouCompleteMe/NeoComplete/Deocomplete etc. Have you used other editors? What is your opinion?
