From 781b92c3f1bbf88252c6de7fbddc386c0c0c26b4 Mon Sep 17 00:00:00 2001
From: Thalia Archibald <thalia@archibald.dev>
Date: Sat, 5 Apr 2025 18:18:31 -0700
Subject: [PATCH] Implement AsRef<OsStr> for Cow<'_, Path>

In #31751, `impl AsRef<Path> for Cow<'_, OsStr>` was added, but the
converse was omitted and it wasn't mentioned in discussion. This seems
to have been a simple oversight, as it otherwise implemented traits
mutually between `OsStr` and `Path`.
---
 library/std/src/path.rs              | 8 ++++++++
 src/tools/compiletest/src/runtest.rs | 2 +-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/library/std/src/path.rs b/library/std/src/path.rs
index 980213be7ea..6d3ec9d4c63 100644
--- a/library/std/src/path.rs
+++ b/library/std/src/path.rs
@@ -3173,6 +3173,14 @@ impl AsRef<OsStr> for Path {
     }
 }
 
+#[stable(feature = "cow_path_as_ref_os_str", since = "CURRENT_RUSTC_VERSION")]
+impl AsRef<OsStr> for Cow<'_, Path> {
+    #[inline]
+    fn as_ref(&self) -> &OsStr {
+        self.as_os_str()
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl fmt::Debug for Path {
     fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
diff --git a/src/tools/compiletest/src/runtest.rs b/src/tools/compiletest/src/runtest.rs
index c8a60b68da8..1c0339ab26a 100644
--- a/src/tools/compiletest/src/runtest.rs
+++ b/src/tools/compiletest/src/runtest.rs
@@ -941,7 +941,7 @@ impl<'test> TestCx<'test> {
             .arg("-L")
             .arg(aux_dir)
             .arg("-o")
-            .arg(out_dir.as_ref())
+            .arg(out_dir)
             .arg("--deny")
             .arg("warnings")
             .arg(&self.testpaths.file)