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//! Regression test for https://github.com/rust-lang/rust/issues/15924
//@ run-pass
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 = ();
}
// This function uses higher-ranked trait bounds, which previously caused ICE
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)
}
// Structure with HRTB constraint that was problematic
struct Foo<T: for<'a> Encodable<JsonEncoder<'a>>> {
v: T,
}
// Drop implementation that exercises the HRTB bounds
impl<T: for<'a> Encodable<JsonEncoder<'a>>> Drop for Foo<T> {
fn drop(&mut self) {
let _ = encode_json(&self.v);
}
}
fn main() {
let _ = Foo { v: 10 };
}
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