Internally tagged enum equivalent?

[BezBIS]

I suspect the answer to this question may be no, but is there any way of replicating Serde's internally tagged enum representation in SQLX? I'm working on a project that uses the concept of 'vague dates' where the date range of an event happening may be known (e.g. 2025-11-01 to 2025-11-05), even though the exact date isn't. Internally, the existing database represents this with three fields: vague_date_type (Varchar), vague_date_start (Date), & vague_date_end (Date) - which may be prefixed if a table stores more than one Vague Date. Depending on the 'type' of Vague Date, the start and end dates may or may not be null. Storing a Vague Date will never need more than these three columns.

Ideally, I'd like to represent this structure in Rust as some form of an Enum, so that the correct fields are always enforced:

enum VagueDate {
    Day {
        start: NaiveDate 
    },
    Before {
      end: NaiveDate  
    },
    Month {
        start: NaiveDate,
        end: NaiveDate
    },
    Unknown
}

Is there any way of performing this conversion using sqlx's traits? Or would I have to use an intermediate struct and TryFrom?