Address a few more nits

Author: compiler-errors

compiler/rustc_hir_analysis/src/variance/mod.rs

@@ -110,13 +110,14 @@ fn variance_of_opaque(tcx: TyCtxt<'_>, item_def_id: LocalDefId) -> &[ty::Varianc
 
         #[instrument(level = "trace", skip(self), ret)]
         fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
-            // FIXME(alias): merge these
             match t.kind() {
-                ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs }) => self.visit_opaque(*def_id, substs),
-                ty::Alias(ty::Projection, proj)
-                    if self.tcx.def_kind(proj.def_id) == DefKind::ImplTraitPlaceholder =>
+                ty::Alias(_, ty::AliasTy { def_id, substs })
+                    if matches!(
+                        self.tcx.def_kind(*def_id),
+                        DefKind::OpaqueTy | DefKind::ImplTraitPlaceholder
+                    ) =>
                 {
-                    self.visit_opaque(proj.def_id, proj.substs)
+                    self.visit_opaque(*def_id, substs)
                 }
                 _ => t.super_visit_with(self),
             }

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -338,13 +338,14 @@ pub fn unexpected_hidden_region_diagnostic<'tcx>(
 
 impl<'tcx> InferCtxt<'tcx> {
     pub fn get_impl_future_output_ty(&self, ty: Ty<'tcx>) -> Option<Ty<'tcx>> {
-        // FIXME(alias): Merge these
         let (def_id, substs) = match *ty.kind() {
-            ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs }) => (def_id, substs),
-            ty::Alias(ty::Projection, data)
-                if self.tcx.def_kind(data.def_id) == DefKind::ImplTraitPlaceholder =>
+            ty::Alias(_, ty::AliasTy { def_id, substs })
+                if matches!(
+                    self.tcx.def_kind(def_id),
+                    DefKind::OpaqueTy | DefKind::ImplTraitPlaceholder
+                ) =>
             {
-                (data.def_id, data.substs)
+                (def_id, substs)
             }
             _ => return None,
         };
@@ -1730,7 +1731,6 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                 TypeError::Sorts(values) => {
                     let extra = expected == found;
                     let sort_string = |ty: Ty<'tcx>, path: Option<PathBuf>| {
-                        // FIXME(alias): Merge these
                         let mut s = match (extra, ty.kind()) {
                             (true, ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. })) => {
                                 let sm = self.tcx.sess.source_map();