embed_migrations! warning: unused import: EmbedMigrations

[pjenvey]

Beginning w/ diesel 1.3 (seen on rust 1.26.0 stable), the embed_migrations! macro produces a rustc warning:

warning: unused import: `EmbedMigrations`
   --> autopush_rs/src/lib.rs:136:1
    |
136 | embed_migrations!();
    | ^^^^^^^^^^^^^^^^^^^^
    |
    = note: #[warn(unused_imports)] on by default
    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)

(A couple others on the gitter have also reported seeing it)

[sgrif]

Can you provide a minimal crate to reproduce the issue? Can you also provide the output of building with -Z external-macro-backtrace on a nightly compiler?

[pjenvey]

Minimal crate: https://github.com/pjenvey/diesel1739

Not sure the external-macro-backtrace is too helpful here:

warning: unused import: `EmbedMigrations`
  --> <embed_migrations macros>:3:14
   |
1  | / (  ) => {
2  | | # [ allow ( dead_code ) ] mod embedded_migrations {
3  | | # [ derive ( EmbedMigrations ) ] struct _Dummy ; } } ; (
   | |              ^^^^^^^^^^^^^^^
4  | | $ migrations_path : expr ) => {
...  |
7  | | embed_migrations_options ( migrations_path = $ migrations_path ) ] struct
8  | | _Dummy ; } }
   | |____________- in this expansion of `embed_migrations!`
   | 
  ::: src/main.rs:10:1
   |
10 |   embed_migrations!();
   |   -------------------- in this macro invocation
   |
   = note: #[warn(unused_imports)] on by default

    Finished dev [unoptimized + debuginfo] target(s) in 47.02s

[Eijebong]

cargo expand:

#![feature(prelude_import)]
#![no_std]
#[prelude_import]
use std::prelude::v1::*;
extern crate diesel;
#[macro_use]
extern crate diesel_migrations;
#[macro_use]
extern crate std;

fn main() {
    ::io::_print(::std::fmt::Arguments::new_v1(
        &["Hello, world!\n"],
        &match () {
            () => [],
        },
    ));
}
#[allow(dead_code)]
mod embedded_migrations {
    struct _Dummy;
    extern crate diesel;
    extern crate diesel_migrations;
    use self::diesel_migrations::*;
    use self::diesel::migration::*;
    use self::diesel::connection::SimpleConnection;
    use std::io;
    const ALL_MIGRATIONS: &[&Migration] =
        &[&EmbeddedMigration{version: "20180220220249",
                             up_sql:
                                 "CREATE TABLE broadcastsv1 (\n    broadcaster_id VARCHAR(64) NOT NULL,\n    bchannel_id VARCHAR(128) NOT NULL,\n    created TIMESTAMP DEFAULT CURRENT_TIMESTAMP NOT NULL,\n    last_updated TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP NOT NULL,\n    version VARCHAR(200) NOT NULL,\n    PRIMARY KEY(broadcaster_id, bchannel_id)\n);\n",}];
    struct EmbeddedMigration {
        version: &'static str,
        up_sql: &'static str,
    }
    impl Migration for EmbeddedMigration {
        fn version(&self) -> &str {
            self.version
        }
        fn run(&self, conn: &SimpleConnection) -> Result<(), RunMigrationsError> {
            conn.batch_execute(self.up_sql).map_err(Into::into)
        }
        fn revert(&self, _conn: &SimpleConnection) -> Result<(), RunMigrationsError> {
            {
                {
                    ::rt::begin_panic(
                        "internal error: entered unreachable code",
                        &("src/main.rs", 10u32, 1u32),
                    )
                }
            }
        }
    }
    pub fn run<C: MigrationConnection>(conn: &C) -> Result<(), RunMigrationsError> {
        run_with_output(conn, &mut io::sink())
    }
    pub fn run_with_output<C: MigrationConnection>(
        conn: &C,
        out: &mut io::Write,
    ) -> Result<(), RunMigrationsError> {
        run_migrations(conn, ALL_MIGRATIONS.iter().map(|v| *v), out)
    }

[rockstar]

Can we cut a release of diesel_migrations so that this change is in a released version?