Can FormattedDateTime implement Yokeable ?

[Baptistemontan]

I need a way to move a FormattedDateTime with it's formatter wrapped in a Rc<DateTimeFormatter>, I thought I could use yoke for that but it seams like FormattedDateTime is invariant due to the underlyings ZeroMap, is there a way to archieve what I want ?

[Manishearth]

Can you expand on your reason to wish to hold on to the FormattedDateTime? it's really intended to be a short lived type.

In theory it's not invariant: ZeroMaps hit a limitation in the compiler, so in theory it could implement Yokeable with prove_covariance_manually, but in practice I'm not convinced it's worth it since I don't see a strong use case.

[sffc]

FormattedDateTime is designed as a temporary, short-lived object to be converted immediately into a storage type: usually a String but possibly a Vec of parts (if you need formatToParts).