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//@ run-pass
#![allow(unused_imports)]
#![allow(unused_must_use)]
use std::fmt;
use std::marker::PhantomData;
trait Encoder {
type Error;
}
trait Encodable<S: Encoder> {
fn encode(&self, s: &mut S) -> Result<(), S::Error>;
}
impl<S: Encoder> Encodable<S> for i32 {
fn encode(&self, _s: &mut S) -> Result<(), S::Error> {
Ok(())
}
}
struct JsonEncoder<'a>(PhantomData<&'a mut ()>);
impl Encoder for JsonEncoder<'_> {
type Error = ();
}
fn encode_json<T: for<'r> Encodable<JsonEncoder<'r>>>(
object: &T,
) -> Result<String, ()> {
let s = String::new();
{
let mut encoder = JsonEncoder(PhantomData);
object.encode(&mut encoder)?;
}
Ok(s)
}
struct Foo<T: for<'a> Encodable<JsonEncoder<'a>>> {
v: T,
}
impl<T: for<'a> Encodable<JsonEncoder<'a>>> Drop for Foo<T> {
fn drop(&mut self) {
encode_json(&self.v);
}
}
fn main() {
let _ = Foo { v: 10 };
}
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