Add opt_alias_variances and use it in outlives code

3 files changed, 11 insertions, 13 deletions

diff --git a/compiler/rustc_infer/src/infer/outlives/for_liveness.rs b/compiler/rustc_infer/src/infer/outlives/for_liveness.rs
index c02ab98b2ba..379410641fe 100644
--- a/compiler/rustc_infer/src/infer/outlives/for_liveness.rs
+++ b/compiler/rustc_infer/src/infer/outlives/for_liveness.rs
@@ -48,7 +48,7 @@ where
             return ty.super_visit_with(self);
         }
 
-        match ty.kind() {
+        match *ty.kind() {
             // We can prove that an alias is live two ways:
             // 1. All the components are live.
             //
@@ -95,11 +95,9 @@ where
                     assert!(r.type_flags().intersects(ty::TypeFlags::HAS_FREE_REGIONS));
                     r.visit_with(self);
                 } else {
-                    // Skip lifetime parameters that are not captures.
-                    let variances = match kind {
-                        ty::Opaque => Some(self.tcx.variances_of(*def_id)),
-                        _ => None,
-                    };
+                    // Skip lifetime parameters that are not captured, since they do
+                    // not need to be live.
+                    let variances = tcx.opt_alias_variances(kind, def_id);
 
                     for (idx, s) in args.iter().enumerate() {
                         if variances.map(|variances| variances[idx]) != Some(ty::Bivariant) {
diff --git a/compiler/rustc_infer/src/infer/outlives/obligations.rs b/compiler/rustc_infer/src/infer/outlives/obligations.rs
index 84e51b18dc5..86a47426049 100644
--- a/compiler/rustc_infer/src/infer/outlives/obligations.rs
+++ b/compiler/rustc_infer/src/infer/outlives/obligations.rs
@@ -392,13 +392,13 @@ where
         // the problem is to add `T: 'r`, which isn't true. So, if there are no
         // inference variables, we use a verify constraint instead of adding
         // edges, which winds up enforcing the same condition.
-        let is_opaque = alias_ty.kind(self.tcx) == ty::Opaque;
+        let kind = alias_ty.kind(self.tcx);
         if approx_env_bounds.is_empty()
             && trait_bounds.is_empty()
-            && (alias_ty.has_infer_regions() || is_opaque)
+            && (alias_ty.has_infer_regions() || kind == ty::Opaque)
         {
             debug!("no declared bounds");
-            let opt_variances = is_opaque.then(|| self.tcx.variances_of(alias_ty.def_id));
+            let opt_variances = self.tcx.opt_alias_variances(kind, alias_ty.def_id);
             self.args_must_outlive(alias_ty.args, origin, region, opt_variances);
             return;
         }
diff --git a/compiler/rustc_infer/src/infer/outlives/verify.rs b/compiler/rustc_infer/src/infer/outlives/verify.rs
index d68f3639176..c14c288c6e4 100644
--- a/compiler/rustc_infer/src/infer/outlives/verify.rs
+++ b/compiler/rustc_infer/src/infer/outlives/verify.rs
@@ -102,12 +102,11 @@ impl<'cx, 'tcx> VerifyBoundCx<'cx, 'tcx> {
 
     #[instrument(level = "debug", skip(self))]
     pub(crate) fn alias_bound(&self, alias_ty: ty::AliasTy<'tcx>) -> VerifyBound<'tcx> {
-        let alias_ty_as_ty = alias_ty.to_ty(self.tcx);
-
         // Search the env for where clauses like `P: 'a`.
         let env_bounds = self.approx_declared_bounds_from_env(alias_ty).into_iter().map(|binder| {
             if let Some(ty::OutlivesPredicate(ty, r)) = binder.no_bound_vars()
-                && ty == alias_ty_as_ty
+                && let ty::Alias(_, alias_ty_from_bound) = *ty.kind()
+                && alias_ty_from_bound == alias_ty
             {
                 // Micro-optimize if this is an exact match (this
                 // occurs often when there are no region variables
@@ -127,7 +126,8 @@ impl<'cx, 'tcx> VerifyBoundCx<'cx, 'tcx> {
         // see the extensive comment in projection_must_outlive
         let recursive_bound = {
             let mut components = smallvec![];
-            compute_alias_components_recursive(self.tcx, alias_ty_as_ty, &mut components);
+            let kind = alias_ty.kind(self.tcx);
+            compute_alias_components_recursive(self.tcx, kind, alias_ty, &mut components);
             self.bound_from_components(&components)
         };