Deprecate rustc-serialize attribute

[brson]

AFAIK the attribute itself is still undeprecated. Just filing an issue to track it.

[brson]

Can this be don for 1.20?

[eddyb]

Do you mean the RustcEncodable and RustcDecodable derives? Or something else?

[brson]

@eddyb Er yes that's what I mean.

[Mark-Simulacrum]

I believe on the implementation side technically https://github.com/rust-lang/rust/blob/master/src/libsyntax_ext/deriving/mod.rs#L119 is what needs to change, but it's worth noting that the Rust compiler itself rather extensively uses these attributes: ~430 of each excluding tests currently, I believe. Maybe it is too early to do this? Or perhaps these attributes are different in some way?

[eddyb]

If the traits from the crates.io library are deprecated instead of the derives, and rustc's copy of the library is left untouched, I believe the derives will trigger the deprecation warnings, but only for users of the crates.io library and Rust won't have a thousand errors while building.

[leroycep]

Is this still an issue?

[Centril]

Closing in favor of rust-lang-deprecated/rustc-serialize#193.