From 46cebf30e9335131d0a669e615f9176fb0b95a6b Mon Sep 17 00:00:00 2001
From: Changyuan Lyu <changyuanl@google.com>
Date: Sat, 1 Aug 2026 23:40:04 -0700
Subject: [PATCH] fix(errors): track callers of BoxTrace::box_trace

Without the marker, error location points to errors.rs instead of the
caller of box_trace.

Signed-off-by: Changyuan Lyu <changyuanl@google.com>
---
 alioth/src/errors.rs        |  1 +
 alioth/tests/errors_test.rs | 39 +++++++++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+)
 create mode 100644 alioth/tests/errors_test.rs

diff --git a/alioth/src/errors.rs b/alioth/src/errors.rs
index f8d2b3be..deb94d27 100644
--- a/alioth/src/errors.rs
+++ b/alioth/src/errors.rs
@@ -30,6 +30,7 @@ impl Error for Box<dyn DebugTrace + Send + Sync + 'static> {
 }
 
 pub trait BoxTrace<'a, T> {
+    #[track_caller]
     fn box_trace<C, E>(self, context: C) -> Result<T, E>
     where
         C: IntoError<E, Source = Box<dyn DebugTrace + Send + Sync + 'a>>,
diff --git a/alioth/tests/errors_test.rs b/alioth/tests/errors_test.rs
new file mode 100644
index 00000000..ca855f26
--- /dev/null
+++ b/alioth/tests/errors_test.rs
@@ -0,0 +1,39 @@
+// Copyright 2026 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use alioth::errors::{BoxTrace, DebugTrace};
+use alioth_macros::trace_error;
+use assert_matches::assert_matches;
+use snafu::Snafu;
+
+#[trace_error]
+#[derive(Snafu, DebugTrace)]
+#[snafu(module, visibility(pub), context(suffix(false)))]
+pub enum Error {
+    #[snafu(display("source error"))]
+    Source,
+    #[snafu(display("any error"))]
+    Any {
+        source: Box<dyn DebugTrace + Send + Sync + 'static>,
+    },
+}
+
+#[test]
+fn test_boxed_error_location() {
+    let e1 = error::Source.build();
+    let r: Result<(), _> = Err(e1).box_trace(error::Any);
+    let e2 = r.unwrap_err();
+    let location = assert_matches! {e2, Error::Any {  _location, .. } => _location};
+    assert_eq!(location.file(), file!());
+}