We should have some symbol to explicitly say that the protocol conformance’s implementation is to be generated by compiler (e.g. Codable, Hashable, Equatable).
Some declarations can be hard to see if it matchs the protocol due to typos.
It would also make the intend clearer if programmers are rolling their own implementations.
I’m thinking something along the line of
class foo: @autogenerate(Codable) {
}