Hi,
I am getting the following error:
msgpack.rs:545:0: 555:1 error: conflicting implementations for a trait
msgpack.rs:545 pub impl<D: DecoderWithMap,
msgpack.rs:546 K: serialize::Decodable<D>,
msgpack.rs:547 V: serialize::Decodable<D>> ~[(K,V)]:
serialize::Decodable<D> {
msgpack.rs:548 static fn decode(&self, d: &D) -> ~[(K,V)] {
msgpack.rs:549 do d.read_map |len| {
msgpack.rs:550 do vec::from_fn(len) |i| {
...
msgpack.rs:539:0: 543:1 note: note conflicting implementation here
msgpack.rs:539 pub impl<D: DecoderWithMap, T> T: serialize::Decodable<D> {
msgpack.rs:540 static fn decode(&self, d: &D) -> T {
msgpack.rs:541 serialize::Decodable::decode(d as &serialize::Decoder)
msgpack.rs:542 }
msgpack.rs:543 }
It's obvious that the two trait implementations conflict, as the one
(for T) is
more general as the other (for ~[(K,V)]). Is there anything I can do to
fix it?
I have found this discussion [1] but I see no solution to the problem.
For msgpack, I want to support "maps". They are specially encoded, so I
need a
special Decoder (serialize::Decoder does not support maps in any way).
Above I
tried to extend the serialize::Decoder trait for read_map() and
read_map_elt(),
leading to DecoderWithMap:
pub trait DecoderWithMap : serialize::Decoder {
fn read_map<T>(&self, f: fn(uint) ⟶ T) ⟶ T;
fn read_map_elt<T>(&self, _idx: uint, f: fn() ⟶ T) ⟶ T;
}
Then I tried to implement Decodable for ~[(K,V)] (which I want to use as
a rust
representation as a map; here I'd probably run into problems again as
serializer defines a generic implementation for ~[] and for tuples...
this at least I could solve by using a different type).
Now I would need to reimplement Decodable for any type I use, so I tried
to use the second generic trait implementation. But this is where it failed
with a conflict.
Would it be possible to "override" a standard (more generic) trait
implementation,
either implicitly (like C++ is doing) or explictly?
Best,
Michael
[1]: https://github.com/mozilla/rust/issues/3429
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