From 851e715e5a7ac21007b9491c81916e854fbab22c Mon Sep 17 00:00:00 2001
From: Jason Newcomb <jsnewcomb@pm.me>
Date: Wed, 16 Mar 2022 12:00:27 -0400
Subject: [PATCH] Don't lint `ptr_arg` on `&mut Cow<_>`

---
 clippy_lints/src/ptr.rs | 2 +-
 tests/ui/ptr_arg.rs     | 7 +++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/clippy_lints/src/ptr.rs b/clippy_lints/src/ptr.rs
index 9c776437d..ba1997e70 100644
--- a/clippy_lints/src/ptr.rs
+++ b/clippy_lints/src/ptr.rs
@@ -436,7 +436,7 @@ fn check_fn_args<'cx, 'tcx: 'cx>(
                             DerefTy::Path,
                             None,
                         ),
-                        Some(sym::Cow) => {
+                        Some(sym::Cow) if mutability == Mutability::Not => {
                             let ty_name = name.args
                                 .and_then(|args| {
                                     args.args.iter().find_map(|a| match a {
diff --git a/tests/ui/ptr_arg.rs b/tests/ui/ptr_arg.rs
index 97990fedd..03dd938a2 100644
--- a/tests/ui/ptr_arg.rs
+++ b/tests/ui/ptr_arg.rs
@@ -194,3 +194,10 @@ fn two_vecs(a: &mut Vec<u32>, b: &mut Vec<u32>) {
     a.push(0);
     b.push(1);
 }
+
+// Issue #8495
+fn cow_conditional_to_mut(a: &mut Cow<str>) {
+    if a.is_empty() {
+        a.to_mut().push_str("foo");
+    }
+}