"bincode does not support Deserializer::deserialize"

[mikedilger]

Is this something that could be implemented, or does it mean my code is doing something wrong?

I'm trying to deserialize a chrono::NaiveDateTime which bincode serialized just fine.

[mikedilger]

Actually it serialized as "2016-08-16T16:41:52.757059590"... which I guess breaks the "no fluff" premise of bincode... but I think the way serde is designed it leaves things up to the type definer so not much can be done about that AFAIK.

[dtolnay]

Looks like a bug in chrono.

https://github.com/lifthrasiir/rust-chrono/blob/d50546a5925b8689f6bcca7155a7af89f2839a32/src/naive/datetime.rs#L892

It should be calling deserializer.deserialize_str instead of deserializer.deserialize.

@mikedilger to understand why this is a problem: deserialize expects the deserializer to be able to tell from the input what data type is there. For example JSON can see a curly brace { and know that that means a map, or it can see a quote " and know that that means a string. For performance reasons bincode does not serialize any of this fluff punctuation so it has no way to tell from the input what type is there. Serde handles this by letting Deserialize implementations hint to the deserializer what type it expects to deserialize, which they do by calling methods like deserialize_str instead of plain deserialize.

[dtolnay]

I made a chrono PR with a fix chronotope/chrono#89.

[lifthrasiir]

@mikedilger

Actually it serialized as "2016-08-16T16:41:52.757059590"... which I guess breaks the "no fluff" premise of bincode...

I plan to do something about that in Chrono 0.3. As far as I understand, the ability to change the representation per the (de)serializer is heavily dependent of the specialization.

[mikedilger]

@dtolnay @lifthrasiir Thanks!