From d9165b2ed6e944ab40d0ea6051c3cfe51568b52e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?R=C3=A9my=20Rakic?= <remy.rakic+github@gmail.com>
Date: Tue, 21 Jan 2025 15:54:00 +0000
Subject: [PATCH 1/2] add test for issue 135289

---
 tests/ui/resolve/auxiliary/fake_matches.rs      | 13 +++++++++++++
 ...t-with-typo-in-pattern-binding-ice-135289.rs | 17 +++++++++++++++++
 2 files changed, 30 insertions(+)
 create mode 100644 tests/ui/resolve/auxiliary/fake_matches.rs
 create mode 100644 tests/ui/resolve/const-with-typo-in-pattern-binding-ice-135289.rs

diff --git a/tests/ui/resolve/auxiliary/fake_matches.rs b/tests/ui/resolve/auxiliary/fake_matches.rs
new file mode 100644
index 0000000000000..6d42972cbace0
--- /dev/null
+++ b/tests/ui/resolve/auxiliary/fake_matches.rs
@@ -0,0 +1,13 @@
+// Helper for test tests/ui/resolve/const-with-typo-in-pattern-binding-ice-135289.rs
+
+//@ edition: 2018
+
+#[macro_export]
+macro_rules! assert_matches {
+    ( $e:expr , $($pat:pat)|+ ) => {
+        match $e {
+            $($pat)|+ => (),
+            _ => (),
+        }
+    };
+}
diff --git a/tests/ui/resolve/const-with-typo-in-pattern-binding-ice-135289.rs b/tests/ui/resolve/const-with-typo-in-pattern-binding-ice-135289.rs
new file mode 100644
index 0000000000000..8267a9250ec93
--- /dev/null
+++ b/tests/ui/resolve/const-with-typo-in-pattern-binding-ice-135289.rs
@@ -0,0 +1,17 @@
+// This is a non-regression test for issue 135289, where the "const with typo in pattern" diagnostic
+// caused an ICE when unexpectedly pretty printing a type for unreachable arms via a macro defined
+// in a dependency.
+
+#![warn(unreachable_patterns)] // needed to reproduce the ICE described in #135289
+
+//@ check-pass
+//@ aux-build: fake_matches.rs
+extern crate fake_matches;
+
+const _A: u64 = 0;
+pub fn f() -> u64 {
+    0
+}
+fn main() {
+    fake_matches::assert_matches!(f(), _non_existent);
+}

From 9bad0daef66d5968969e79428d8bc46b98e2627f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?R=C3=A9my=20Rakic?= <remy.rakic+github@gmail.com>
Date: Tue, 21 Jan 2025 16:18:34 +0000
Subject: [PATCH 2/2] add fixme in typoed const pattern lint

---
 compiler/rustc_mir_build/src/thir/pattern/check_match.rs | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
index 6631086720068..b5b7b54a1cc39 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
@@ -1086,6 +1086,12 @@ fn find_fallback_pattern_typo<'tcx>(
                 let vis = cx.tcx.visibility(item.owner_id);
                 if vis.is_accessible_from(parent, cx.tcx) {
                     accessible.push(item_name);
+                    // FIXME: the line below from PR #135310 is a workaround for the ICE in issue
+                    // #135289, where a macro in a dependency can create unreachable patterns in the
+                    // current crate. Path trimming expects diagnostics for a typoed const, but no
+                    // diagnostics are emitted and we ICE. See
+                    // `tests/ui/resolve/const-with-typo-in-pattern-binding-ice-135289.rs` for a
+                    // test that reproduces the ICE if we don't use `with_no_trimmed_paths!`.
                     let path = with_no_trimmed_paths!(cx.tcx.def_path_str(item.owner_id));
                     accessible_path.push(path);
                 } else if name == item_name {