Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I was trying to be have the API be consistent across the Hierarchy.
ParseResult(value/error, type) matches Parsed(value, type) and NotParsed(error, type)

I thought it made it easier to see the relation between the constructors better, but I can revert it if you prefer having the parameter orders not match.