Auto merge of #2885 - RalfJung:rustup, r=RalfJung

Rustup

11 files changed, 146 insertions, 70 deletions

diff --git a/compiler/rustc_hir_analysis/src/astconv/mod.rs b/compiler/rustc_hir_analysis/src/astconv/mod.rs
index 5ee0cf94360..6ac1df6a079 100644
--- a/compiler/rustc_hir_analysis/src/astconv/mod.rs
+++ b/compiler/rustc_hir_analysis/src/astconv/mod.rs
@@ -2419,6 +2419,10 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             return Ok(None);
         }
 
+        //
+        // Select applicable inherent associated type candidates modulo regions.
+        //
+
         // In contexts that have no inference context, just make a new one.
         // We do need a local variable to store it, though.
         let infcx_;
@@ -2431,7 +2435,9 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             }
         };
 
-        let param_env = tcx.param_env(block.owner.to_def_id());
+        // FIXME(inherent_associated_types): Acquiring the ParamEnv this early leads to cycle errors
+        // when inside of an ADT (#108491) or where clause.
+        let param_env = tcx.param_env(block.owner);
         let cause = ObligationCause::misc(span, block.owner.def_id);
 
         let mut fulfillment_errors = Vec::new();
@@ -2439,6 +2445,8 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             let universe = infcx.create_next_universe();
 
             // Regions are not considered during selection.
+            // FIXME(non_lifetime_binders): Here we are "truncating" or "flattening" the universes
+            // of type and const binders. Is that correct in the selection phase? See also #109505.
             let self_ty = tcx.replace_escaping_bound_vars_uncached(
                 self_ty,
                 FnMutDelegate {
@@ -2454,41 +2462,40 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
 
             candidates
                 .iter()
-                .filter_map(|&(impl_, (assoc_item, def_scope))| {
+                .copied()
+                .filter(|&(impl_, _)| {
                     infcx.probe(|_| {
                         let ocx = ObligationCtxt::new_in_snapshot(&infcx);
 
-                        let impl_ty = tcx.type_of(impl_);
                         let impl_substs = infcx.fresh_item_substs(impl_);
-                        let impl_ty = impl_ty.subst(tcx, impl_substs);
+                        let impl_ty = tcx.type_of(impl_).subst(tcx, impl_substs);
                         let impl_ty = ocx.normalize(&cause, param_env, impl_ty);
 
-                        // Check that the Self-types can be related.
-                        // FIXME(fmease): Should we use `eq` here?
-                        ocx.sup(&ObligationCause::dummy(), param_env, impl_ty, self_ty).ok()?;
+                        // Check that the self types can be related.
+                        // FIXME(inherent_associated_types): Should we use `eq` here? Method probing uses
+                        // `sup` for this situtation, too. What for? To constrain inference variables?
+                        if ocx.sup(&ObligationCause::dummy(), param_env, impl_ty, self_ty).is_err()
+                        {
+                            return false;
+                        }
 
                         // Check whether the impl imposes obligations we have to worry about.
-                        let impl_bounds = tcx.predicates_of(impl_);
-                        let impl_bounds = impl_bounds.instantiate(tcx, impl_substs);
-
+                        let impl_bounds = tcx.predicates_of(impl_).instantiate(tcx, impl_substs);
                         let impl_bounds = ocx.normalize(&cause, param_env, impl_bounds);
-
                         let impl_obligations = traits::predicates_for_generics(
                             |_, _| cause.clone(),
                             param_env,
                             impl_bounds,
                         );
-
                         ocx.register_obligations(impl_obligations);
 
                         let mut errors = ocx.select_where_possible();
                         if !errors.is_empty() {
                             fulfillment_errors.append(&mut errors);
-                            return None;
+                            return false;
                         }
 
-                        // FIXME(fmease): Unsolved vars can escape this InferCtxt snapshot.
-                        Some((assoc_item, def_scope, infcx.resolve_vars_if_possible(impl_substs)))
+                        true
                     })
                 })
                 .collect()
@@ -2497,24 +2504,26 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         if applicable_candidates.len() > 1 {
             return Err(self.complain_about_ambiguous_inherent_assoc_type(
                 name,
-                applicable_candidates.into_iter().map(|(candidate, ..)| candidate).collect(),
+                applicable_candidates.into_iter().map(|(_, (candidate, _))| candidate).collect(),
                 span,
             ));
         }
 
-        if let Some((assoc_item, def_scope, impl_substs)) = applicable_candidates.pop() {
+        if let Some((impl_, (assoc_item, def_scope))) = applicable_candidates.pop() {
             self.check_assoc_ty(assoc_item, name, def_scope, block, span);
 
-            // FIXME(inherent_associated_types): To fully *confirm* the *probed* candidate, we still
-            // need to relate the Self-type with fresh item substs & register region obligations for
-            // regionck to prove/disprove.
-
-            let item_substs =
-                self.create_substs_for_associated_item(span, assoc_item, segment, impl_substs);
+            // FIXME(fmease): Currently creating throwaway `parent_substs` to please
+            // `create_substs_for_associated_item`. Modify the latter instead (or sth. similar) to
+            // not require the parent substs logic.
+            let parent_substs = InternalSubsts::identity_for_item(tcx, impl_);
+            let substs =
+                self.create_substs_for_associated_item(span, assoc_item, segment, parent_substs);
+            let substs = tcx.mk_substs_from_iter(
+                std::iter::once(ty::GenericArg::from(self_ty))
+                    .chain(substs.into_iter().skip(parent_substs.len())),
+            );
 
-            // FIXME(fmease, #106722): Check if the bounds on the parameters of the
-            // associated type hold, if any.
-            let ty = tcx.type_of(assoc_item).subst(tcx, item_substs);
+            let ty = tcx.mk_alias(ty::Inherent, tcx.mk_alias_ty(assoc_item, substs));
 
             return Ok(Some((ty, assoc_item)));
         }
diff --git a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
index 7384eb25f2e..8bf1e0e84a4 100644
--- a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
+++ b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
@@ -60,19 +60,21 @@ pub(super) fn compare_impl_method<'tcx>(
     };
 }
 
-/// This function is best explained by example. Consider a trait:
+/// This function is best explained by example. Consider a trait with it's implementation:
 ///
-///     trait Trait<'t, T> {
-///         // `trait_m`
-///         fn method<'a, M>(t: &'t T, m: &'a M) -> Self;
-///     }
+/// ```rust
+/// trait Trait<'t, T> {
+///     // `trait_m`
+///     fn method<'a, M>(t: &'t T, m: &'a M) -> Self;
+/// }
 ///
-/// And an impl:
+/// struct Foo;
 ///
-///     impl<'i, 'j, U> Trait<'j, &'i U> for Foo {
-///          // `impl_m`
-///          fn method<'b, N>(t: &'j &'i U, m: &'b N) -> Foo;
-///     }
+/// impl<'i, 'j, U> Trait<'j, &'i U> for Foo {
+///     // `impl_m`
+///     fn method<'b, N>(t: &'j &'i U, m: &'b N) -> Foo { Foo }
+/// }
+/// ```
 ///
 /// We wish to decide if those two method types are compatible.
 /// For this we have to show that, assuming the bounds of the impl hold, the
@@ -82,7 +84,9 @@ pub(super) fn compare_impl_method<'tcx>(
 /// type parameters to impl type parameters. This is taken from the
 /// impl trait reference:
 ///
-///     trait_to_impl_substs = {'t => 'j, T => &'i U, Self => Foo}
+/// ```rust,ignore (pseudo-Rust)
+/// trait_to_impl_substs = {'t => 'j, T => &'i U, Self => Foo}
+/// ```
 ///
 /// We create a mapping `dummy_substs` that maps from the impl type
 /// parameters to fresh types and regions. For type parameters,
@@ -91,13 +95,17 @@ pub(super) fn compare_impl_method<'tcx>(
 /// regions (Note: but only early-bound regions, i.e., those
 /// declared on the impl or used in type parameter bounds).
 ///
-///     impl_to_placeholder_substs = {'i => 'i0, U => U0, N => N0 }
+/// ```rust,ignore (pseudo-Rust)
+/// impl_to_placeholder_substs = {'i => 'i0, U => U0, N => N0 }
+/// ```
 ///
 /// Now we can apply `placeholder_substs` to the type of the impl method
 /// to yield a new function type in terms of our fresh, placeholder
 /// types:
 ///
-///     <'b> fn(t: &'i0 U0, m: &'b) -> Foo
+/// ```rust,ignore (pseudo-Rust)
+/// <'b> fn(t: &'i0 U0, m: &'b) -> Foo
+/// ```
 ///
 /// We now want to extract and substitute the type of the *trait*
 /// method and compare it. To do so, we must create a compound
@@ -106,11 +114,15 @@ pub(super) fn compare_impl_method<'tcx>(
 /// type parameters. We extend the mapping to also include
 /// the method parameters.
 ///
-///     trait_to_placeholder_substs = { T => &'i0 U0, Self => Foo, M => N0 }
+/// ```rust,ignore (pseudo-Rust)
+/// trait_to_placeholder_substs = { T => &'i0 U0, Self => Foo, M => N0 }
+/// ```
 ///
 /// Applying this to the trait method type yields:
 ///
-///     <'a> fn(t: &'i0 U0, m: &'a) -> Foo
+/// ```rust,ignore (pseudo-Rust)
+/// <'a> fn(t: &'i0 U0, m: &'a) -> Foo
+/// ```
 ///
 /// This type is also the same but the name of the bound region (`'a`
 /// vs `'b`). However, the normal subtyping rules on fn types handle
@@ -1163,7 +1175,7 @@ fn compare_self_type<'tcx>(
 /// as the number of generics on the respective assoc item in the trait definition.
 ///
 /// For example this code emits the errors in the following code:
-/// ```
+/// ```rust,compile_fail
 /// trait Trait {
 ///     fn foo();
 ///     type Assoc<T>;
@@ -1547,7 +1559,7 @@ fn compare_synthetic_generics<'tcx>(
 /// the same kind as the respective generic parameter in the trait def.
 ///
 /// For example all 4 errors in the following code are emitted here:
-/// ```
+/// ```rust,ignore (pseudo-Rust)
 /// trait Foo {
 ///     fn foo<const N: u8>();
 ///     type bar<const N: u8>;
diff --git a/compiler/rustc_hir_analysis/src/coherence/orphan.rs b/compiler/rustc_hir_analysis/src/coherence/orphan.rs
index 5ce8a83aad7..272177dfbd0 100644
--- a/compiler/rustc_hir_analysis/src/coherence/orphan.rs
+++ b/compiler/rustc_hir_analysis/src/coherence/orphan.rs
@@ -210,6 +210,19 @@ fn do_orphan_check_impl<'tcx>(
                 NonlocalImpl::DisallowOther,
             ),
 
+            // ```
+            // struct S<T>(T);
+            // impl<T: ?Sized> S<T> {
+            //     type This = T;
+            // }
+            // impl<T: ?Sized> AutoTrait for S<T>::This {}
+            // ```
+            // FIXME(inherent_associated_types): The example code above currently leads to a cycle
+            ty::Alias(AliasKind::Inherent, _) => (
+                LocalImpl::Disallow { problematic_kind: "associated type" },
+                NonlocalImpl::DisallowOther,
+            ),
+
             // type Opaque = impl Trait;
             // impl AutoTrait for Opaque {}
             ty::Alias(AliasKind::Opaque, _) => (
diff --git a/compiler/rustc_hir_analysis/src/collect/generics_of.rs b/compiler/rustc_hir_analysis/src/collect/generics_of.rs
index 119933697a1..ab2932bf969 100644
--- a/compiler/rustc_hir_analysis/src/collect/generics_of.rs
+++ b/compiler/rustc_hir_analysis/src/collect/generics_of.rs
@@ -51,7 +51,15 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
                 // of a const parameter type, e.g. `struct Foo<const N: usize, const M: [u8; N]>` is not allowed.
                 None
             } else if tcx.lazy_normalization() {
-                if let Some(param_id) = tcx.hir().opt_const_param_default_param_def_id(hir_id) {
+                let parent_node = tcx.hir().get_parent(hir_id);
+                if let Node::Variant(Variant { disr_expr: Some(constant), .. }) = parent_node
+                    && constant.hir_id == hir_id
+                {
+                    // enum variant discriminants are not allowed to use any kind of generics
+                    None
+                } else if let Some(param_id) =
+                    tcx.hir().opt_const_param_default_param_def_id(hir_id)
+                {
                     // If the def_id we are calling generics_of on is an anon ct default i.e:
                     //
                     // struct Foo<const N: usize = { .. }>;
@@ -94,15 +102,15 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
                         has_self: generics.has_self,
                         has_late_bound_regions: generics.has_late_bound_regions,
                     };
+                } else {
+                    // HACK(eddyb) this provides the correct generics when
+                    // `feature(generic_const_expressions)` is enabled, so that const expressions
+                    // used with const generics, e.g. `Foo<{N+1}>`, can work at all.
+                    //
+                    // Note that we do not supply the parent generics when using
+                    // `min_const_generics`.
+                    Some(parent_def_id.to_def_id())
                 }
-
-                // HACK(eddyb) this provides the correct generics when
-                // `feature(generic_const_expressions)` is enabled, so that const expressions
-                // used with const generics, e.g. `Foo<{N+1}>`, can work at all.
-                //
-                // Note that we do not supply the parent generics when using
-                // `min_const_generics`.
-                Some(parent_def_id.to_def_id())
             } else {
                 let parent_node = tcx.hir().get_parent(hir_id);
                 match parent_node {
@@ -115,11 +123,6 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
                     {
                         Some(parent_def_id.to_def_id())
                     }
-                    Node::Variant(Variant { disr_expr: Some(constant), .. })
-                        if constant.hir_id == hir_id =>
-                    {
-                        Some(parent_def_id.to_def_id())
-                    }
                     Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) => {
                         Some(tcx.typeck_root_def_id(def_id.to_def_id()))
                     }
diff --git a/compiler/rustc_hir_analysis/src/collect/predicates_of.rs b/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
index 6c06957d1ee..e04658c8e77 100644
--- a/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
+++ b/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
@@ -657,14 +657,15 @@ pub(super) fn implied_predicates_with_filter(
         &*tcx.arena.alloc_from_iter(superbounds.predicates().chain(where_bounds_that_match));
     debug!(?implied_bounds);
 
-    // Now require that immediate supertraits are converted,
-    // which will, in turn, reach indirect supertraits.
+    // Now require that immediate supertraits are converted, which will, in
+    // turn, reach indirect supertraits, so we detect cycles now instead of
+    // overflowing during elaboration.
     if matches!(filter, PredicateFilter::SelfOnly) {
-        // Now require that immediate supertraits are converted,
-        // which will, in turn, reach indirect supertraits.
         for &(pred, span) in implied_bounds {
             debug!("superbound: {:?}", pred);
-            if let ty::PredicateKind::Clause(ty::Clause::Trait(bound)) = pred.kind().skip_binder() {
+            if let ty::PredicateKind::Clause(ty::Clause::Trait(bound)) = pred.kind().skip_binder()
+                && bound.polarity == ty::ImplPolarity::Positive
+            {
                 tcx.at(span).super_predicates_of(bound.def_id());
             }
         }
diff --git a/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
index ab0dd01ce3a..5c7f7f10b17 100644
--- a/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
+++ b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
@@ -1923,7 +1923,7 @@ fn is_late_bound_map(
     /// handles cycle detection as we go through the query system.
     ///
     /// This is necessary in the first place for the following case:
-    /// ```
+    /// ```rust,ignore (pseudo-Rust)
     /// type Alias<'a, T> = <T as Trait<'a>>::Assoc;
     /// fn foo<'a>(_: Alias<'a, ()>) -> Alias<'a, ()> { ... }
     /// ```
@@ -1948,7 +1948,7 @@ fn is_late_bound_map(
                 ty::Param(param_ty) => {
                     self.arg_is_constrained[param_ty.index as usize] = true;
                 }
-                ty::Alias(ty::Projection, _) => return ControlFlow::Continue(()),
+                ty::Alias(ty::Projection | ty::Inherent, _) => return ControlFlow::Continue(()),
                 _ => (),
             }
             t.super_visit_with(self)
diff --git a/compiler/rustc_hir_analysis/src/collect/type_of.rs b/compiler/rustc_hir_analysis/src/collect/type_of.rs
index c20fbfd1e40..8df0166f76b 100644
--- a/compiler/rustc_hir_analysis/src/collect/type_of.rs
+++ b/compiler/rustc_hir_analysis/src/collect/type_of.rs
@@ -127,7 +127,7 @@ fn anon_const_type_of<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> Ty<'tcx> {
             // the def_id that this query was called with. We filter to only type and const args here
             // as a precaution for if it's ever allowed to elide lifetimes in GAT's. It currently isn't
             // but it can't hurt to be safe ^^
-            if let ty::Alias(ty::Projection, projection) = ty.kind() {
+            if let ty::Alias(ty::Projection | ty::Inherent, projection) = ty.kind() {
                 let generics = tcx.generics_of(projection.def_id);
 
                 let arg_index = segment
diff --git a/compiler/rustc_hir_analysis/src/constrained_generic_params.rs b/compiler/rustc_hir_analysis/src/constrained_generic_params.rs
index e18b0f08279..9200c2aecf5 100644
--- a/compiler/rustc_hir_analysis/src/constrained_generic_params.rs
+++ b/compiler/rustc_hir_analysis/src/constrained_generic_params.rs
@@ -59,7 +59,7 @@ struct ParameterCollector {
 impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ParameterCollector {
     fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
         match *t.kind() {
-            ty::Alias(ty::Projection, ..) if !self.include_nonconstraining => {
+            ty::Alias(ty::Projection | ty::Inherent, ..) if !self.include_nonconstraining => {
                 // projections are not injective
                 return ControlFlow::Continue(());
             }
diff --git a/compiler/rustc_hir_analysis/src/errors.rs b/compiler/rustc_hir_analysis/src/errors.rs
index 379a88538a9..6e7eb4f6cdc 100644
--- a/compiler/rustc_hir_analysis/src/errors.rs
+++ b/compiler/rustc_hir_analysis/src/errors.rs
@@ -815,6 +815,15 @@ pub(crate) struct ClosureImplicitHrtb {
 }
 
 #[derive(Diagnostic)]
+#[diag(hir_analysis_empty_specialization)]
+pub(crate) struct EmptySpecialization {
+    #[primary_span]
+    pub span: Span,
+    #[note]
+    pub base_impl_span: Span,
+}
+
+#[derive(Diagnostic)]
 #[diag(hir_analysis_const_specialize)]
 pub(crate) struct ConstSpecialize {
     #[primary_span]
diff --git a/compiler/rustc_hir_analysis/src/impl_wf_check/min_specialization.rs b/compiler/rustc_hir_analysis/src/impl_wf_check/min_specialization.rs
index 5cca2dacb5c..e84da2519ae 100644
--- a/compiler/rustc_hir_analysis/src/impl_wf_check/min_specialization.rs
+++ b/compiler/rustc_hir_analysis/src/impl_wf_check/min_specialization.rs
@@ -80,7 +80,7 @@ use rustc_middle::ty::{self, TyCtxt, TypeVisitableExt};
 use rustc_span::Span;
 use rustc_trait_selection::traits::error_reporting::TypeErrCtxtExt;
 use rustc_trait_selection::traits::outlives_bounds::InferCtxtExt as _;
-use rustc_trait_selection::traits::{self, translate_substs, wf, ObligationCtxt};
+use rustc_trait_selection::traits::{self, translate_substs_with_cause, wf, ObligationCtxt};
 
 pub(super) fn check_min_specialization(tcx: TyCtxt<'_>, impl_def_id: LocalDefId) {
     if let Some(node) = parent_specialization_node(tcx, impl_def_id) {
@@ -100,12 +100,19 @@ fn parent_specialization_node(tcx: TyCtxt<'_>, impl1_def_id: LocalDefId) -> Opti
         // Implementing a normal trait isn't a specialization.
         return None;
     }
+    if trait_def.is_marker {
+        // Overlapping marker implementations are not really specializations.
+        return None;
+    }
     Some(impl2_node)
 }
 
 /// Check that `impl1` is a sound specialization
 #[instrument(level = "debug", skip(tcx))]
 fn check_always_applicable(tcx: TyCtxt<'_>, impl1_def_id: LocalDefId, impl2_node: Node) {
+    let span = tcx.def_span(impl1_def_id);
+    check_has_items(tcx, impl1_def_id, impl2_node, span);
+
     if let Some((impl1_substs, impl2_substs)) = get_impl_substs(tcx, impl1_def_id, impl2_node) {
         let impl2_def_id = impl2_node.def_id();
         debug!(?impl2_def_id, ?impl2_substs);
@@ -116,7 +123,6 @@ fn check_always_applicable(tcx: TyCtxt<'_>, impl1_def_id: LocalDefId, impl2_node
             unconstrained_parent_impl_substs(tcx, impl2_def_id, impl2_substs)
         };
 
-        let span = tcx.def_span(impl1_def_id);
         check_constness(tcx, impl1_def_id, impl2_node, span);
         check_static_lifetimes(tcx, &parent_substs, span);
         check_duplicate_params(tcx, impl1_substs, &parent_substs, span);
@@ -124,6 +130,13 @@ fn check_always_applicable(tcx: TyCtxt<'_>, impl1_def_id: LocalDefId, impl2_node
     }
 }
 
+fn check_has_items(tcx: TyCtxt<'_>, impl1_def_id: LocalDefId, impl2_node: Node, span: Span) {
+    if let Node::Impl(impl2_id) = impl2_node && tcx.associated_item_def_ids(impl1_def_id).is_empty() {
+        let base_impl_span = tcx.def_span(impl2_id);
+        tcx.sess.emit_err(errors::EmptySpecialization { span, base_impl_span });
+    }
+}
+
 /// Check that the specializing impl `impl1` is at least as const as the base
 /// impl `impl2`
 fn check_constness(tcx: TyCtxt<'_>, impl1_def_id: LocalDefId, impl2_node: Node, span: Span) {
@@ -167,8 +180,21 @@ fn get_impl_substs(
         ocx.assumed_wf_types(param_env, tcx.def_span(impl1_def_id), impl1_def_id);
 
     let impl1_substs = InternalSubsts::identity_for_item(tcx, impl1_def_id);
-    let impl2_substs =
-        translate_substs(infcx, param_env, impl1_def_id.to_def_id(), impl1_substs, impl2_node);
+    let impl1_span = tcx.def_span(impl1_def_id);
+    let impl2_substs = translate_substs_with_cause(
+        infcx,
+        param_env,
+        impl1_def_id.to_def_id(),
+        impl1_substs,
+        impl2_node,
+        |_, span| {
+            traits::ObligationCause::new(
+                impl1_span,
+                impl1_def_id,
+                traits::ObligationCauseCode::BindingObligation(impl2_node.def_id(), span),
+            )
+        },
+    );
 
     let errors = ocx.select_all_or_error();
     if !errors.is_empty() {
diff --git a/compiler/rustc_hir_analysis/src/outlives/implicit_infer.rs b/compiler/rustc_hir_analysis/src/outlives/implicit_infer.rs
index d53c429ca15..0cd2fc1aa29 100644
--- a/compiler/rustc_hir_analysis/src/outlives/implicit_infer.rs
+++ b/compiler/rustc_hir_analysis/src/outlives/implicit_infer.rs
@@ -210,6 +210,9 @@ fn insert_required_predicates_to_be_wf<'tcx>(
                 );
             }
 
+            // FIXME(inherent_associated_types): Handle this case properly.
+            ty::Alias(ty::Inherent, _) => {}
+
             _ => {}
         }
     }