Fail, Occur, and ParsingStyle could all have legitimate reasons to gain options in the future, so for 0.3 we should mark them #[non_exhaustive].
It may also be worth doing some renaming to make things more consistent with the rest of the ecosystem:
Fail -> ErrorOccur::Req -> RequiredOccur::Multi -> Occur::ZeroOrMore
Fail,Occur, andParsingStylecould all have legitimate reasons to gain options in the future, so for 0.3 we should mark them#[non_exhaustive].It may also be worth doing some renaming to make things more consistent with the rest of the ecosystem:
Fail->ErrorOccur::Req->RequiredOccur::Multi->Occur::ZeroOrMore