+// FIXME: switch to something more ergonomic here, once available.
+// (Currently there is no way to opt into sysroot crates without `extern crate`.)
+#[allow(unused_extern_crates)]
+extern crate rustc_driver;
+#[allow(unused_extern_crates)]
+extern crate rustc_plugin;
+use self::rustc_plugin::Registry;