Pre-RfC: #[auto_derive] for generating #[deriving(...)] decorators

internals ideas (deprecated)
2

Copying my prior-art comment from Reddit:

Haskell supports a form of generics that allows (with some effort on the part of the trait author, like this RFC):

class Serialize a where
  put :: a -> [Bit]
 
  default put :: (Generic a, GSerialize (Rep a)) => a -> [Bit]
  put a = gput (from a)

  get :: [Bit] -> (a, [Bit])
 
  default get :: (Generic a, GSerialize (Rep a)) => [Bit] -> (a, [Bit])
  get xs = (to x, xs')
    where (x, xs') = gget xs

-- ...stuff...
 
data UserTree a = Node a (UserTree a) (UserTree a) | Leaf
  deriving (Generic, Show)
 
instance (Serialize a) => Serialize (UserTree a)

which ‘derives’ an impl of the custom Serialize trait for the custom UserTree type. (In Rust terminology.)

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