Error messages for poly variant syntax error are hard to understand

[arnarthor]

type apiKeyError
   = [|`Dev |`Prod];
type validationErrors = [ | `AnalyticsPlatformMissing | `ApiKeyMissing(apiKeyError)];

This just gives a generic kinda cryptic syntax error message with no context and my editor (Emacs) pointed me to the later type decleration (CLI did point to the correct line).
As soon as I change it to [ |`Dev |`Prod] it reformats just fine.

Wondering if it's possible to detect something like this since it's probably quite common due to the similarities with array and poly variant declaration.

[hcarty]

This is more forward looking, but there are/may be plans to add custom array types to the core language. See ocaml/ocaml#616. That shouldn't hold this particular issue up! Just a note that there may be a real use for type = [| ... |]; as a syntax in the future.