the trait `sqlx_core::executor::Executor<'_>` is not implemented

[grantcarthew]

Hi,

Just testing out sqlx for a project and the todo example fails. I followed the README.

# rustc 1.44.0 (49cae5576 2020-06-01)
# cargo 1.44.0 (05d080faa 2020-05-06)
# Postgres v12
# cargo run output:

grant@gdc:/data/sqlx/examples/postgres/todos$ cargo run -- add "todo thingy"
   Compiling sqlx-example-postgres-todos v0.1.0 (/data/sqlx/examples/postgres/todos)
error[E0277]: the trait bound `&mut &sqlx_core::pool::Pool<sqlx_core::postgres::database::Postgres>: sqlx_core::executor::Executor<'_>` is not satisfied
  --> examples/postgres/todos/src/main.rs:58:16
   |
58 |     .fetch_one(&mut pool)
   |                -^^^^^^^^
   |                |
   |                the trait `sqlx_core::executor::Executor<'_>` is not implemented for `&mut &sqlx_core::pool::Pool<sqlx_core::postgres::database::Postgres>`
   |                help: consider removing the leading `&`-reference
   |
   = help: the following implementations were found:
             <&sqlx_core::pool::Pool<DB> as sqlx_core::executor::Executor<'p>>

error[E0277]: the trait bound `&mut &sqlx_core::pool::Pool<sqlx_core::postgres::database::Postgres>: sqlx_core::executor::Executor<'_>` is not satisfied
  --> examples/postgres/todos/src/main.rs:73:14
   |
73 |     .execute(&mut pool)
   |              -^^^^^^^^
   |              |
   |              the trait `sqlx_core::executor::Executor<'_>` is not implemented for `&mut &sqlx_core::pool::Pool<sqlx_core::postgres::database::Postgres>`
   |              help: consider removing the leading `&`-reference
   |
   = help: the following implementations were found:
             <&sqlx_core::pool::Pool<DB> as sqlx_core::executor::Executor<'p>>

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0277`.
error: could not compile `sqlx-example-postgres-todos`.

To learn more, run the command again with --verbose.

I'm new to rust. This is the first bit of work I have done with it.

[abonander]

There's a lot of churn on master right now as we prep for 0.4, does this still happen if you checkout the v0.3.5 tag?

[grantcarthew]

Hi @abonander and thanks for your help.

Yes, it seems it is the changes in master that are causing the issue with the examples.

Once I switched to v0.3.5 it ran like a dream.

Is there a reference for the changes? I think I'll be settling for this crate to talk to the database.

Thanks again.

[mehcode]

@grantcarthew In SQLx v0.1 and v0.2 we only had Executor implemented for &mut &Pool. This proved to be very confusing for users so we worked to make Executor also be implemented by &Pool (harder than it sounds) in v0.3. Now on master (soon to be v0.4) we removed the &mut &Pool implementation which cleaned up some internal code and makes it easier to extend Executor (in that vein, there are new methods available now like fetch_many() and execute_many()).

[grantcarthew]

OK, more to learn. Thanks @mehcode. I'm looking forward to getting this working.