associated_type.rs

// smoelius: Associated types are considered a legitimate reason to put a bound on a struct
// parameter. See:
// * https://github.com/rust-lang/rust-clippy/issues/1689
// * https://github.com/rust-lang/api-guidelines/issues/6
//
// This example is based in part on:
// https://docs.serde.rs/serde_json/#creating-json-by-serializing-data-structures

use serde::{de::DeserializeOwned, Deserialize, Serialize};

trait Serializable {
    type Out: Clone + DeserializeOwned + Serialize + PartialEq + Eq;
    fn serialize(&self) -> Self::Out;
}

impl<T> Serializable for T
where
    T: Serialize,
{
    type Out = String;
    fn serialize(&self) -> Self::Out {
        serde_json::to_string(self).unwrap()
    }
}

#[test_fuzz::test_fuzz(generic_args = "Address", bounds = "T: Serializable")]
fn serializes_to<T>(x: &T, y: &T::Out) -> bool
where
    T: Clone + DeserializeOwned + Serialize + Serializable,
{
    &<T as Serializable>::serialize(x) == y
}

#[derive(Clone, Serialize, Deserialize)]
struct Address {
    street: String,
    city: String,
}

#[test]
fn test() {
    let address = Address {
        street: "10 Downing Street".to_owned(),
        city: "London".to_owned(),
    };

    assert!(serializes_to(
        &address,
        &String::from("{\"street\":\"10 Downing Street\",\"city\":\"London\"}")
    ));
}