Complex Serialisation

[28Smiles]

This is a first draft on complex type serialisation #6. The code is in heavy development and a complete mess.
To be as maintainable as possible the macro creates internal structs and uses the serde::Serialize macro for serialisation, where possible.

Implementation State

Serialisation:

• Unit Modus (serialize as an integer type)
• Externally Tagged ({"42": { ... }})
• Internally Tagged ({"tag": 42, ... })
• Adjacently Tagged ({"tag": 42, "content": {...}})

Deserialisation:

• Unit Modus (deserialize as an integer type)
• Externally Tagged ({"42": { ... }})
• Internally Tagged ({"tag": 42, ... })
• Adjacently Tagged ({"tag": 42, "content": {...}})

Changes in Behavior of the Previous Macro

I have not found any

Internal Changes of generated Code

• Uses the expression of the variant instead of casting, since this is not possible with non unit variants
• The Unit case is reimplemented, with some minor changes.

[28Smiles]

Serialisation is now fully functional, I will continue working on deserialisation, but this will be harder since i need to work with visitors.

[28Smiles]

I also introduced the const_format crate, since it is the only way for me to create a compiletime static string from an const expression.

[28Smiles]

@dtolnay I hope its okay if I ping you here, I would really appreciate some input from your side.

[28Smiles]

Here an example of the current capabillities

[28Smiles]

Also, i know the code is a complete mess rn, but there are a lot of cases to cover, while beeing heavily codependent, but I will look into modularizing this suff once all represenations are covered.

[28Smiles]

I decided to implement this in the main serde derive macro, since there are a lot of edge cases. With this full support should be garanteed. serde-rs/serde#2354