Whoops, excluded the mailing list.
On 22 March 2014 11:53, Edward Wang <edward.yu.w...@gmail.com> wrote:
> `to_encode_object` has type `Encodable<Encoder<'a>>` so
> `to_encode_object.encode(...)`
> requires an Encoder instance with lifetime 'a, the one defined in the
> struct bound.
>
> The problem I think is that I can't write:
>
> pub fn buffer_encode<T:Encodable<_>>(to_encode_object: &T) -> ~[u8] {
>
> let mut m = MemWriter::new();
> {
> let mut encoder = Encoder::new(&mut m as &mut io::Writer);
> to_encode_object.encode(&mut encoder);
> }
> m.unwrap()
> }
>
> and ask rustc to infer a proper type parameter. That would be global
> inference.
>
> -Ed
>
>
> On Sat, Mar 22, 2014 at 11:43 PM, Josh Matthews <j...@joshmatthews.net>wrote:
>
>> "m here is merely a local variable but Encoder<'a> requires a lifetime at
>> least 'a"
>>
>> This statement does not make sense to me. Why does m's lifetime not
>> satisfy the requirement?
>>
>> Cheers,
>> Josh
>>
>>
>> On 22 March 2014 10:24, Edward Wang <edward.yu.w...@gmail.com> wrote:
>>
>>> Hi,
>>>
>>> I'm in the process of fixing a `ty_trait` variance inference bug, which
>>> will void the following code in json.rs:
>>>
>>> pub struct Encoder<'a> {
>>> priv wr: &'a mut io::Writer,
>>> priv error: io::IoResult<()>,
>>> }
>>> impl<'a> Encoder<'a> {
>>> pub fn new<'a>(wr: &'a mut io::Writer) -> Encoder<'a> {
>>> Encoder { wr: wr, error: Ok(()) }
>>> }
>>>
>>> pub fn buffer_encode<T:Encodable<Encoder<'a>>>(to_encode_object: &T)
>>> -> ~[u8] {
>>> let mut m = MemWriter::new();
>>> {
>>> let mut encoder = Encoder::new(&mut m as &mut io::Writer);
>>> to_encode_object.encode(&mut encoder);
>>> }
>>> m.unwrap()
>>> }
>>> }
>>>
>>> If taking a close look, m here is merely a local variable but
>>> Encoder<'a> requires a lifetime at least 'a. A naive fix would be:
>>>
>>> let mut encoder = Encoder::new(cast::transmute_mut_region(&mut m));
>>>
>>> But of course, it is very uncivilized :) Any suggestion on how to
>>> refactor this piece of code so it won't violate the lifetime requirement?
>>>
>>> Regards,
>>> Edward
>>>
>>> _______________________________________________
>>> Rust-dev mailing list
>>> Rust-dev@mozilla.org
>>> https://mail.mozilla.org/listinfo/rust-dev
>>>
>>>
>>
>
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