3 files changed, 16 insertions, 1 deletions
diff --git a/clippy_utils/src/lib.rs b/clippy_utils/src/lib.rs
index 6c4cec59524..d53cafde45d 100644
--- a/clippy_utils/src/lib.rs
+++ b/clippy_utils/src/lib.rs
@@ -5,6 +5,7 @@
 #![feature(lint_reasons)]
 #![feature(never_type)]
 #![feature(rustc_private)]
+#![feature(assert_matches)]
 #![recursion_limit = "512"]
 #![cfg_attr(feature = "deny-warnings", deny(warnings))]
 #![allow(clippy::missing_errors_doc, clippy::missing_panics_doc, clippy::must_use_candidate)]
diff --git a/clippy_utils/src/ty.rs b/clippy_utils/src/ty.rs
index a05f682aa8c..f0b4ede35fb 100644
--- a/clippy_utils/src/ty.rs
+++ b/clippy_utils/src/ty.rs
@@ -27,6 +27,7 @@ use rustc_target::abi::{Size, VariantIdx};
 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt as _;
 use rustc_trait_selection::traits::query::normalize::QueryNormalizeExt;
 use rustc_trait_selection::traits::{Obligation, ObligationCause};
+use std::assert_matches::debug_assert_matches;
 use std::iter;
 
 use crate::{match_def_path, path_res, paths};
@@ -259,7 +260,11 @@ pub fn implements_trait_with_env_from_iter<'tcx>(
             })),
     );
 
-    debug_assert_eq!(tcx.def_kind(trait_id), DefKind::Trait);
+    debug_assert_matches!(
+        tcx.def_kind(trait_id),
+        DefKind::Trait | DefKind::TraitAlias,
+        "`DefId` must belong to a trait or trait alias"
+    );
     #[cfg(debug_assertions)]
     assert_generic_args_match(tcx, trait_id, trait_ref.args);
 
diff --git a/tests/ui/crashes/ice-11337.rs b/tests/ui/crashes/ice-11337.rs
new file mode 100644
index 00000000000..0bed4035f6b
--- /dev/null
+++ b/tests/ui/crashes/ice-11337.rs
@@ -0,0 +1,9 @@
+#![feature(trait_alias)]
+
+trait Confusing<F> = Fn(i32) where F: Fn(u32);
+
+fn alias<T: Confusing<F>, F>(_: T, _: F) {}
+
+fn main() {
+    alias(|_| {}, |_| {});
+}