serialize::json is encouraging allocating intermediate buffers

[huonw]

The Encodable/Decodable interface is designed to avoid having to allocate everything to intermediate buffers, but json is encouraging going via String. serialize::json has the top level encode function returning a String, and all the examples use encode directly, there's no demonstration of the good direct-to-Writer API.

That is, something like

println!("{}", json::encode(&x))

can be written a little like

encodable.encode(&mut json::Encoder::new(&mut io::stdout()))

If that is deemed too ugly, I think we should work on fixing the ergonomics of the good version, rather than just leaping straight to the -> String ones (e.g. json::encode(&mut io::stdout(), &x) would be nice, and work with json::encode(&mut some_file, &x), json::encode(&mut some_tcp_stream, &x), etc.).

cc @aturon

[steveklabnik]

This issue has been moved to the rustc-serialize repo: rust-lang-deprecated/rustc-serialize#57