diff --git a/compiler/rustc_trait_selection/src/solve/assembly/mod.rs b/compiler/rustc_trait_selection/src/solve/assembly/mod.rs
index 25cc82f01d5..d14e6244f7d 100644
--- a/compiler/rustc_trait_selection/src/solve/assembly/mod.rs
+++ b/compiler/rustc_trait_selection/src/solve/assembly/mod.rs
@@ -506,10 +506,12 @@ fn assemble_alias_bound_candidates<G: GoalKind<'tcx>>(
             | ty::Param(_)
             | ty::Placeholder(..)
             | ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
+            | ty::Alias(ty::Inherent, _)
             | ty::Error(_) => return,
             ty::Infer(ty::TyVar(_) | ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_))
             | ty::Bound(..) => bug!("unexpected self type for `{goal:?}`"),
-            ty::Alias(_, alias_ty) => alias_ty,
+            // Excluding IATs here as they don't have meaningful item bounds.
+            ty::Alias(ty::Projection | ty::Opaque, alias_ty) => alias_ty,
         };
 
         for assumption in self.tcx().item_bounds(alias_ty.def_id).subst(self.tcx(), alias_ty.substs)
diff --git a/compiler/rustc_trait_selection/src/traits/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs
index 8e684b7ac23..79ecbabb5f7 100644
--- a/compiler/rustc_trait_selection/src/traits/project.rs
+++ b/compiler/rustc_trait_selection/src/traits/project.rs
@@ -1543,7 +1543,10 @@ fn assemble_candidates_from_trait_def<'cx, 'tcx>(
     // Check whether the self-type is itself a projection.
     // If so, extract what we know from the trait and try to come up with a good answer.
     let bounds = match *obligation.predicate.self_ty().kind() {
-        ty::Alias(_, ref data) => tcx.item_bounds(data.def_id).subst(tcx, data.substs),
+        // Excluding IATs here as they don't have meaningful item bounds.
+        ty::Alias(ty::Projection | ty::Opaque, ref data) => {
+            tcx.item_bounds(data.def_id).subst(tcx, data.substs)
+        }
         ty::Infer(ty::TyVar(_)) => {
             // If the self-type is an inference variable, then it MAY wind up
             // being a projected type, so induce an ambiguity.
diff --git a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
index a8fb55df2d3..aa230936903 100644
--- a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
@@ -143,7 +143,8 @@ fn assemble_candidates_from_projected_tys(
         // Before we go into the whole placeholder thing, just
         // quickly check if the self-type is a projection at all.
         match obligation.predicate.skip_binder().trait_ref.self_ty().kind() {
-            ty::Alias(..) => {}
+            // Excluding IATs here as they don't have meaningful item bounds.
+            ty::Alias(ty::Projection | ty::Opaque, _) => {}
             ty::Infer(ty::TyVar(_)) => {
                 span_bug!(
                     obligation.cause.span,
diff --git a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
index 6a648294efd..de023501f9e 100644
--- a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
@@ -156,7 +156,10 @@ fn confirm_projection_candidate(
         let placeholder_self_ty = placeholder_trait_predicate.self_ty();
         let placeholder_trait_predicate = ty::Binder::dummy(placeholder_trait_predicate);
         let (def_id, substs) = match *placeholder_self_ty.kind() {
-            ty::Alias(_, ty::AliasTy { def_id, substs, .. }) => (def_id, substs),
+            // Excluding IATs here as they don't have meaningful item bounds.
+            ty::Alias(ty::Projection | ty::Opaque, ty::AliasTy { def_id, substs, .. }) => {
+                (def_id, substs)
+            }
             _ => bug!("projection candidate for unexpected type: {:?}", placeholder_self_ty),
         };
 
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index b72ff5b78e4..f1bd9f5bbf8 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -1645,7 +1645,9 @@ fn match_projection_obligation_against_definition_bounds(
 
         let tcx = self.infcx.tcx;
         let (def_id, substs) = match *placeholder_trait_predicate.trait_ref.self_ty().kind() {
-            ty::Alias(_, ty::AliasTy { def_id, substs, .. }) => (def_id, substs),
+            ty::Alias(ty::Projection | ty::Opaque, ty::AliasTy { def_id, substs, .. }) => {
+                (def_id, substs)
+            }
             _ => {
                 span_bug!(
                     obligation.cause.span,
diff --git a/src/tools/clippy/tests/ui/issue-111399.rs b/src/tools/clippy/tests/ui/issue-111399.rs
new file mode 100644
index 00000000000..b65e6c7261a
--- /dev/null
+++ b/src/tools/clippy/tests/ui/issue-111399.rs
@@ -0,0 +1,13 @@
+#![feature(inherent_associated_types)]
+#![allow(incomplete_features)]
+
+// Check that rustc doesn't crash on the trait bound `Self::Ty: std::marker::Freeze`.
+
+pub struct Struct;
+
+impl Struct {
+    pub type Ty = usize;
+    pub const CT: Self::Ty = 42;
+}
+
+fn main() {}