vine: impl derivation

[tjjfvi]

Introduce Tuple and Object traits

trait Tuple[Tuple, Init, Rest] {
  fn deconstruct(tuple: Tuple) -> (Init, Rest);
  fn reconstruct(init: Init, rest: Rest) -> Tuple;
}

trait Object[Object, Init, Rest] {
  const key: String;
  fn deconstruct(object: Object) -> (Init, Rest);
  fn reconstruct(init: Init, rest: Rest) -> Object;
}

The compiler would automatically implement Tuple and Object for all non-empty tuple and object types; e.g. Tuple[(A, B, C), A, (B, C)] and Object[{ a: A, b: B, c: C }, A, { b: B, c: C }]. The order in which object types are broken down would not be guaranteed.

This allows traits to be inductively implemented for all tuple/object types by providing impls for (), {}, and types implementing Tuple/Object.

For struct types, introduce an additional trait

trait Struct[Struct, Data] {
  const name: String;
  fn deconstruct(self: Struct) -> Data;
  fn reconstruct(data: Data) -> Struct;
}

Not sure how best to make implementations that use this impl to be opt-in.

Also not sure how best to handle enums.