Fixed one possible error source when encoding hygiene metadata.

Sadly, this isn't the reason the tests fail.

src/librustc/middle/cstore.rs

@@ -253,6 +253,8 @@ pub struct ExternBodyNestedBodies {
 pub trait CrateStore {
     fn crate_data_as_rc_any(&self, krate: CrateNum) -> Rc<Any>;
 
+    fn ensure_hygiene_data_loaded(&self);
+
     // access to the metadata loader
     fn metadata_loader(&self) -> &MetadataLoader;
 
@@ -325,6 +327,7 @@ pub struct DummyCrateStore;
 impl CrateStore for DummyCrateStore {
     fn crate_data_as_rc_any(&self, krate: CrateNum) -> Rc<Any>
         { bug!("crate_data_as_rc_any") }
+    fn ensure_hygiene_data_loaded(&self) { bug!("ensure_hygiene_data_loaded") }
     // item info
     fn visibility_untracked(&self, def: DefId) -> ty::Visibility { bug!("visibility") }
     fn item_generics_cloned_untracked(&self, def: DefId) -> ty::Generics

src/librustc_metadata/cstore_impl.rs

@@ -350,6 +350,12 @@ impl CrateStore for cstore::CStore {
         self.get_crate_data(krate)
     }
 
+    fn ensure_hygiene_data_loaded(&self) {
+        self.iter_crate_data(|_, metadata| {
+            (*metadata).imported_hygiene_data();
+        });
+    }
+
     fn metadata_loader(&self) -> &MetadataLoader {
         &*self.metadata_loader
     }

src/librustc_metadata/decoder.rs

@@ -1271,6 +1271,6 @@ impl<'a, 'tcx> CrateMetadata {
             Some(hygiene::extend_hygiene_data(external_hygiene_data));
         self.hygiene_data_being_decoded.set(false);
 
-        Ref::map(self.hygiene_data_import_info.borrow(), |d| d.as_ref().unwrap());
+        Ref::map(self.hygiene_data_import_info.borrow(), |d| d.as_ref().unwrap())
     }
 }

src/librustc_metadata/encoder.rs

@@ -324,6 +324,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
     }
 
     fn encode_hygiene_data(&mut self) -> Lazy<hygiene::HygieneData> {
+        self.tcx.sess.cstore.ensure_hygiene_data_loaded();
         hygiene::HygieneData::safe_with(|data| self.lazy(data))
     }