get_mut doesn't seem to work

[Manishearth]

I'm not sure what happened here:

extern crate hyper;
use hyper::header::Headers;
use hyper::header::{ContentLength, ContentType};
use hyper::http::RawStatus;
use hyper::method::Method;
use hyper::mime::{Attr as MimeAttr, Value};

fn main() {
    let mut x = Headers::new();
    x.set_raw("Content-Type", vec!["text/plain;charset=shift-jis".bytes().collect()]);

    println!("old: {:?}", x); // charset is shift-jis
    if let Some(old_ct) = x.get_mut::<ContentType>() {
        println!("old old_ct: {:?}", old_ct); // still shift-jis
        let mut new_ct = old_ct.clone();
        for param in (new_ct.0).2.iter_mut() {
            if param.0 == MimeAttr::Charset {
                println!("old param {:?}", param); // shift-jis
                *param = (MimeAttr::Charset, Value::Ext("hi".into()));
                println!("new param {:?}", param); // hi
            }
        }
        *old_ct = new_ct;
        println!("new old_ct: {:?}", old_ct); // hi
    }

    // at this stage I'd expect the header to have changed. But it hasn't.
    println!("new get: {:?}", x.get::<ContentType>()); // hi
    println!("new get raw: {:?}", x.get_raw("content-type")); // shift-jis again??
    println!("new: {:?}", x); // shift-jis again??
}

[Manishearth]

I guess the mixture of raw and non-raw methods is breaking it, but I'm not sure. Does set_raw create two copies of the thing -- one typed, one untyped?

[Manishearth]

I guess the issue is that typed_mut doesn't remove the header from the raw headers when inserting a typed one.

[seanmonstar]

Ah, this is a bug. The invariants I've been enforcing are: if you get an immutable view (raw or typed), and it doesn't exist, it will generate it and then give it to you (either serializing a typed, or parsing a raw). However, if you get a mutable reference, because you can cause them to be out of sync, it should obliterate the other stored value. So, get_mut should kill the raw part. I believe it does this correctly when you do headers.set(Foo), so it's a hole in get_mut.