Fix after rebasing

Author: eholk

compiler/rustc_typeck/src/check/generator_interior.rs

@@ -584,7 +584,7 @@ fn check_must_not_suspend_ty<'tcx>(
         }
         // If drop tracking is enabled, we want to look through references, since the referrent
         // may not be considered live across the await point.
-        ty::Ref(_region, ty, _mutability) if fcx.sess().opts.debugging_opts.drop_tracking => {
+        ty::Ref(_region, ty, _mutability) if fcx.sess().opts.unstable_opts.drop_tracking => {
             let descr_pre = &format!("{}reference{} to ", data.descr_pre, plural_suffix);
             check_must_not_suspend_ty(fcx, ty, hir_id, SuspendCheckData { descr_pre, ..data })
         }

src/test/ui/lint/must_not_suspend/ref-drop-tracking.stderr

@@ -3,7 +3,7 @@ error: reference to `Umm` held across a suspend point, but should not be
    |
 LL |         let guard = &mut self.u;
    |             ^^^^^
-LL | 
+LL |
 LL |         other().await;
    |                ------ the value is held across this suspend point
    |