Add missing extern crate rustc_driver

diff --git a/src/lib.rs b/src/lib.rs
index 1d1ef525f23fa38ba259bdd45ea0e0e6e86a8549..0c27bcacfb83ca73c77744e4ff02b6d640f63215 100644 (file)
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -24,6 +24,11 @@
 extern crate rustc_session;
 extern crate rustc_span;
 
+// Necessary to pull in object code as the rest of the rustc crates are shipped only as rmeta
+// files.
+#[allow(unused_extern_crates)]
+extern crate rustc_driver;
+
 use std::cell::RefCell;
 use std::collections::HashMap;
 use std::fmt;