From 417c09ab2705b38f23b87daa82b1ace0a03a8117 Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Sun, 3 Nov 2019 16:52:27 -0500
Subject: [PATCH] Do not needlessly write-lock

---
 src/librustc_lint/unused.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/librustc_lint/unused.rs b/src/librustc_lint/unused.rs
index af43030d0f2ae..3f85e6d772ec1 100644
--- a/src/librustc_lint/unused.rs
+++ b/src/librustc_lint/unused.rs
@@ -309,7 +309,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedAttributes {
             }
         }
 
-        let plugin_attributes = cx.sess().plugin_attributes.borrow_mut();
+        let plugin_attributes = cx.sess().plugin_attributes.borrow();
         for &(name, ty) in plugin_attributes.iter() {
             if ty == AttributeType::Whitelisted && attr.check_name(name) {
                 debug!("{:?} (plugin attr) is whitelisted with ty {:?}", name, ty);