Maybe related to #1295 but I'm not certain, so submitting a new issue. Under default profile and 0.13.0, I get the following formatting, where polymorphic variants do not have a space before their attributes, while simple variants do, which does not seem right.

type classic = Variant [@attr]

type polymorphic = [ `Variant[@attr] ]

I personally prefer the former (with whitespace) solution, and I don't think it can lead to ambiguous situations.