1 files changed, 22 insertions, 24 deletions

diff --git a/compiler/rustc_hir_analysis/src/variance/mod.rs b/compiler/rustc_hir_analysis/src/variance/mod.rs
index 066e74491..d91d9fcbc 100644
--- a/compiler/rustc_hir_analysis/src/variance/mod.rs
+++ b/compiler/rustc_hir_analysis/src/variance/mod.rs
@@ -7,8 +7,8 @@ use rustc_arena::DroplessArena;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_middle::query::Providers;
-use rustc_middle::ty::{self, CrateVariancesMap, SubstsRef, Ty, TyCtxt};
-use rustc_middle::ty::{TypeSuperVisitable, TypeVisitable};
+use rustc_middle::ty::{self, CrateVariancesMap, GenericArgsRef, Ty, TyCtxt};
+use rustc_middle::ty::{TypeSuperVisitable, TypeVisitable, TypeVisitableExt};
 use std::ops::ControlFlow;
 
 /// Defines the `TermsContext` basically houses an arena where we can
@@ -56,7 +56,14 @@ fn variances_of(tcx: TyCtxt<'_>, item_def_id: LocalDefId) -> &[ty::Variance] {
             let crate_map = tcx.crate_variances(());
             return crate_map.variances.get(&item_def_id.to_def_id()).copied().unwrap_or(&[]);
         }
-        DefKind::OpaqueTy | DefKind::ImplTraitPlaceholder => {
+        DefKind::TyAlias { lazy }
+            if lazy || tcx.type_of(item_def_id).instantiate_identity().has_opaque_types() =>
+        {
+            // These are inferred.
+            let crate_map = tcx.crate_variances(());
+            return crate_map.variances.get(&item_def_id.to_def_id()).copied().unwrap_or(&[]);
+        }
+        DefKind::OpaqueTy => {
             return variance_of_opaque(tcx, item_def_id);
         }
         _ => {}
@@ -83,17 +90,17 @@ fn variance_of_opaque(tcx: TyCtxt<'_>, item_def_id: LocalDefId) -> &[ty::Varianc
 
     impl<'tcx> OpaqueTypeLifetimeCollector<'tcx> {
         #[instrument(level = "trace", skip(self), ret)]
-        fn visit_opaque(&mut self, def_id: DefId, substs: SubstsRef<'tcx>) -> ControlFlow<!> {
+        fn visit_opaque(&mut self, def_id: DefId, args: GenericArgsRef<'tcx>) -> ControlFlow<!> {
             if def_id != self.root_def_id && self.tcx.is_descendant_of(def_id, self.root_def_id) {
                 let child_variances = self.tcx.variances_of(def_id);
-                for (a, v) in substs.iter().zip(child_variances) {
+                for (a, v) in args.iter().zip(child_variances) {
                     if *v != ty::Bivariant {
                         a.visit_with(self)?;
                     }
                 }
                 ControlFlow::Continue(())
             } else {
-                substs.visit_with(self)
+                args.visit_with(self)
             }
         }
     }
@@ -110,18 +117,10 @@ 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> {
             match t.kind() {
-                ty::Alias(_, ty::AliasTy { def_id, substs, .. })
+                ty::Alias(_, ty::AliasTy { def_id, args, .. })
                     if matches!(self.tcx.def_kind(*def_id), DefKind::OpaqueTy) =>
                 {
-                    self.visit_opaque(*def_id, substs)
-                }
-                // FIXME(-Zlower-impl-trait-in-trait-to-assoc-ty) check whether this is necessary
-                // at all for RPITITs.
-                ty::Alias(_, ty::AliasTy { def_id, substs, .. })
-                    if self.tcx.is_impl_trait_in_trait(*def_id)
-                        && !self.tcx.lower_impl_trait_in_trait_to_assoc_ty() =>
-                {
-                    self.visit_opaque(*def_id, substs)
+                    self.visit_opaque(*def_id, args)
                 }
                 _ => t.super_visit_with(self),
             }
@@ -152,30 +151,29 @@ fn variance_of_opaque(tcx: TyCtxt<'_>, item_def_id: LocalDefId) -> &[ty::Varianc
 
     let mut collector =
         OpaqueTypeLifetimeCollector { tcx, root_def_id: item_def_id.to_def_id(), variances };
-    let id_substs = ty::InternalSubsts::identity_for_item(tcx, item_def_id);
-    for (pred, _) in tcx.explicit_item_bounds(item_def_id).subst_iter_copied(tcx, id_substs) {
+    let id_args = ty::GenericArgs::identity_for_item(tcx, item_def_id);
+    for (pred, _) in tcx.explicit_item_bounds(item_def_id).iter_instantiated_copied(tcx, id_args) {
         debug!(?pred);
 
-        // We only ignore opaque type substs if the opaque type is the outermost type.
+        // We only ignore opaque type args if the opaque type is the outermost type.
         // The opaque type may be nested within itself via recursion in e.g.
         // type Foo<'a> = impl PartialEq<Foo<'a>>;
         // which thus mentions `'a` and should thus accept hidden types that borrow 'a
         // instead of requiring an additional `+ 'a`.
         match pred.kind().skip_binder() {
             ty::ClauseKind::Trait(ty::TraitPredicate {
-                trait_ref: ty::TraitRef { def_id: _, substs, .. },
-                constness: _,
+                trait_ref: ty::TraitRef { def_id: _, args, .. },
                 polarity: _,
             }) => {
-                for subst in &substs[1..] {
+                for subst in &args[1..] {
                     subst.visit_with(&mut collector);
                 }
             }
             ty::ClauseKind::Projection(ty::ProjectionPredicate {
-                projection_ty: ty::AliasTy { substs, .. },
+                projection_ty: ty::AliasTy { args, .. },
                 term,
             }) => {
-                for subst in &substs[1..] {
+                for subst in &args[1..] {
                     subst.visit_with(&mut collector);
                 }
                 term.visit_with(&mut collector);