mirror of https://github.com/rust-lang/rust
54 lines
974 B
Rust
54 lines
974 B
Rust
//@ run-pass
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#![allow(unused_imports)]
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#![allow(unused_must_use)]
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//@ pretty-expanded FIXME #23616
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use std::fmt;
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use std::marker::PhantomData;
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trait Encoder {
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type Error;
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}
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trait Encodable<S: Encoder> {
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fn encode(&self, s: &mut S) -> Result<(), S::Error>;
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}
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impl<S: Encoder> Encodable<S> for i32 {
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fn encode(&self, _s: &mut S) -> Result<(), S::Error> {
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Ok(())
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}
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}
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struct JsonEncoder<'a>(PhantomData<&'a mut ()>);
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impl Encoder for JsonEncoder<'_> {
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type Error = ();
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}
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fn encode_json<T: for<'r> Encodable<JsonEncoder<'r>>>(
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object: &T,
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) -> Result<String, ()> {
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let s = String::new();
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{
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let mut encoder = JsonEncoder(PhantomData);
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object.encode(&mut encoder)?;
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}
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Ok(s)
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}
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struct Foo<T: for<'a> Encodable<JsonEncoder<'a>>> {
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v: T,
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}
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impl<T: for<'a> Encodable<JsonEncoder<'a>>> Drop for Foo<T> {
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fn drop(&mut self) {
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encode_json(&self.v);
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}
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}
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fn main() {
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let _ = Foo { v: 10 };
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}
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