fix(errors): track callers of BoxTrace::box_trace

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>>,

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!());
+}