Attempting to serialize a struct with for example ??u32 can lead to invalid deserialization in binary, as there is no way to tell the difference between ??u32 as being null or ?u32 as being null.
Attempting to serialize a struct with for example `??u32` can lead to invalid deserialization in binary, as there is no way to tell the difference between `??u32` as being `null` or `?u32` as being `null`.