Enabling #[serde(deserialize_with=...)]

[halzy]

The code had been returning errors too early to allow for deserialize_with to work. If the visitor does not receive the expected type, it'll try deserialize_any so that conversions can happen.

[RReverser]

Hmm why does deserialize_with care about speicialized methods at all? I assumed it would just be called instead of whatever is defined as default implementation?