I got this simple trait:

pub trait Delete<C> {
    type Error;

    /// Delete the row in the database.
    fn delete(&self, conn: C) -> impl Future<Output = Result<(), Self::Error>>;
}

And I want to implement it directly for the corresponding pool object in SQLx:

impl<T> Delete<sqlx::SqlitePool> for T
where
    T: for<'a> Delete<&'a mut sqlx::SqliteConnection>,
{
    type Error = <T as Delete<&mut sqlx::SqliteConnection>>::Error;

    async fn delete(&self, conn: sqlx::SqlitePool) -> Result<(), Self::Error> {
        let mut conn = conn.acquire().await?;
        self.delete(&mut *conn).await
    }
}

However rust want me to specify the lifetime of the reference in the associated type Error... Which I don't have. And if I add a reference to the implementation, rust tell me that the variable conn doesn't live long enough due to the lifetime being referenced in the output type

error[E0597]: `conn` does not live long enough
  --> src/table/delete.rs:17:27
   |
15 |     async fn delete(&self, conn: sqlx::SqlitePool) -> Result<(), Self::Error> {
   |                                                       ----------------------- return type of async function is Result<(), <T as delete::Delete<&'1 mut SqliteConnection>>::Error>
16 |         let mut conn = conn.acquire().await.unwrap();
   |             -------- binding `conn` declared here
17 |         self.delete(&mut *conn).await
   |         ------------------^^^^-
   |         |                 |
   |         |                 borrowed value does not live long enough
   |         argument requires that `conn` is borrowed for `'1`
18 |     }
   |     - `conn` dropped here while still borrowed

Is there any trickery I can use to fix that?

2 posts - 2 participants

Read full topic