Fix build

Author: gnzlbg

src/mismatch.rs

@@ -10,7 +10,7 @@ use rustc::{
     hir::def_id::DefId,
     ty::{
         self,
-        relate::{Relate, RelateResult, TraitObjectMode, TypeRelation},
+        relate::{Relate, RelateResult, TypeRelation},
         subst::Substs,
         Ty, TyCtxt,
         Visibility::Public,
@@ -95,10 +95,6 @@ impl<'a, 'gcx, 'tcx> TypeRelation<'a, 'gcx, 'tcx> for MismatchRelation<'a, 'gcx,
         "Mismatch"
     }
 
-    fn trait_object_mode(&self) -> TraitObjectMode {
-        TraitObjectMode::NoSquash
-    }
-
     fn a_is_expected(&self) -> bool {
         true
     }
@@ -186,14 +182,17 @@ impl<'a, 'gcx, 'tcx> TypeRelation<'a, 'gcx, 'tcx> for MismatchRelation<'a, 'gcx,
             }
             (&TyKind::Dynamic(a_obj, a_r), &TyKind::Dynamic(b_obj, b_r)) => {
                 let _ = self.relate(&a_r, &b_r)?;
-                let a = a_obj.principal();
-                let b = b_obj.principal();
-
-                if self.check_substs(a.skip_binder().substs, b.skip_binder().substs) {
-                    let _ = self.relate(&a.skip_binder().substs, &b.skip_binder().substs)?;
-                    Some((a.skip_binder().def_id, b.skip_binder().def_id))
-                } else {
-                    None
+                match (a_obj.principal(), b_obj.principal()) {
+                    (None, _) => None,
+                    (_, None) => None,
+                    (Some(a), Some(b)) => {
+                        if self.check_substs(a.skip_binder().substs, b.skip_binder().substs) {
+                            let _ = self.relate(&a.skip_binder().substs, &b.skip_binder().substs)?;
+                            Some((a.skip_binder().def_id, b.skip_binder().def_id))
+                        } else {
+                            None
+                        }
+                    }
                 }
             }
             (&TyKind::Tuple(as_), &TyKind::Tuple(bs)) => {