From f746e1916999810a1e643077fcb677b077e31bc4 Mon Sep 17 00:00:00 2001
From: y21 <30553356+y21@users.noreply.github.com>
Date: Mon, 14 Aug 2023 19:10:33 +0200
Subject: [PATCH] allow trait alias DefIds in
 `implements_trait_with_env_from_iter`

---
 clippy_utils/src/lib.rs       | 1 +
 clippy_utils/src/ty.rs        | 7 ++++++-
 tests/ui/crashes/ice-11337.rs | 9 +++++++++
 3 files changed, 16 insertions(+), 1 deletion(-)
 create mode 100644 tests/ui/crashes/ice-11337.rs

diff --git a/clippy_utils/src/lib.rs b/clippy_utils/src/lib.rs
index 171b7faf219..64b24c56121 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_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(|_| {}, |_| {});
+}