Implement serde::IntoDeserializer for IndexMap/IndexSet about indexmap

[cuviper]

When would one actually use IntoDeserializer? This is the first I've heard of it.

[Mingun]

For example, at implementation of a new format and structure, the containing IndexMap and similar serde_json::Value -- i.e. the type describing all possible values of the format. For example, I implemented such type in the my serde-gff library and can use it with serde-transcode in the idiomatic way:

extern crate serde;
extern crate serde_json;
extern crate serde_gff;
extern crate serde_transcode;

use serde::Serialize;
use std::io::{Write, BufWriter};
use std::fs::File;

fn main() {
    let value: serde_gff::Value = ...;
    let writer = BufWriter::new(File::create("output.json").unwrap());

    let mut serializer = serde_json::Serializer::pretty(writer);
    serde_transcode::transcode(&mut value.into_deserializer(), &mut serializer).unwrap();
    serializer.into_inner().flush().unwrap();
}

But you not the first who for the first time hears about IntoDeserializer :). This piece really, is not really clear documented.