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/// Constructs a query that finds record(s) based on directional association with other record(s).
///
/// # Example
///
/// ```rust
/// # include!("../doctest_setup.rs");
/// # use schema::{posts, users};
/// #
/// # #[derive(Identifiable, Queryable)]
/// # pub struct User {
/// # id: i32,
/// # name: String,
/// # }
/// #
/// # #[derive(Debug, PartialEq)]
/// # #[derive(Identifiable, Queryable, Associations)]
/// # #[diesel(belongs_to(User))]
/// # pub struct Post {
/// # id: i32,
/// # user_id: i32,
/// # title: String,
/// # }
/// #
/// # fn main() {
/// # run_test();
/// # }
/// #
/// # fn run_test() -> QueryResult<()> {
/// # let connection = &mut establish_connection();
/// # use self::users::dsl::*;
/// # use self::posts::dsl::{posts, title};
/// let sean = users.filter(name.eq("Sean")).first::<User>(connection)?;
/// let tess = users.filter(name.eq("Tess")).first::<User>(connection)?;
///
/// let seans_posts = Post::belonging_to(&sean)
/// .select(title)
/// .load::<String>(connection)?;
/// assert_eq!(vec!["My first post", "About Rust"], seans_posts);
///
/// // A vec or slice can be passed as well
/// let more_posts = Post::belonging_to(&vec![sean, tess])
/// .select(title)
/// .load::<String>(connection)?;
/// assert_eq!(vec!["My first post", "About Rust", "My first post too"], more_posts);
/// # Ok(())
/// # }
/// ```
pub trait BelongingToDsl<T> {
/// The query returned by `belonging_to`
type Output;
/// Get the record(s) belonging to record(s) `other`
fn belonging_to(other: T) -> Self::Output;
}