From 6745e8da06e1fd313d2ff20ff9fe8d8dc4714479 Mon Sep 17 00:00:00 2001
From: John Kugelman <john@kugelman.name>
Date: Mon, 11 Oct 2021 16:15:50 -0400
Subject: Add #[must_use] to len and is_empty

---
 library/std/src/ffi/os_str.rs            | 2 ++
 library/std/src/fs.rs                    | 1 +
 library/std/src/os/unix/net/ancillary.rs | 2 ++
 3 files changed, 5 insertions(+)

(limited to 'library/std/src')

diff --git a/library/std/src/ffi/os_str.rs b/library/std/src/ffi/os_str.rs
index f5cef60e126..ca0f27b285f 100644
--- a/library/std/src/ffi/os_str.rs
+++ b/library/std/src/ffi/os_str.rs
@@ -660,6 +660,7 @@ impl OsStr {
     /// assert!(!os_str.is_empty());
     /// ```
     #[stable(feature = "osstring_simple_functions", since = "1.9.0")]
+    #[must_use]
     #[inline]
     pub fn is_empty(&self) -> bool {
         self.inner.inner.is_empty()
@@ -691,6 +692,7 @@ impl OsStr {
     /// assert_eq!(os_str.len(), 3);
     /// ```
     #[stable(feature = "osstring_simple_functions", since = "1.9.0")]
+    #[must_use]
     #[inline]
     pub fn len(&self) -> usize {
         self.inner.inner.len()
diff --git a/library/std/src/fs.rs b/library/std/src/fs.rs
index 726c855c4fd..54b998d12ac 100644
--- a/library/std/src/fs.rs
+++ b/library/std/src/fs.rs
@@ -1077,6 +1077,7 @@ impl Metadata {
     ///     Ok(())
     /// }
     /// ```
+    #[must_use]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn len(&self) -> u64 {
         self.0.size()
diff --git a/library/std/src/os/unix/net/ancillary.rs b/library/std/src/os/unix/net/ancillary.rs
index 1f9d42812ec..0ed3018c802 100644
--- a/library/std/src/os/unix/net/ancillary.rs
+++ b/library/std/src/os/unix/net/ancillary.rs
@@ -430,12 +430,14 @@ impl<'a> SocketAncillary<'a> {
     }
 
     /// Returns `true` if the ancillary data is empty.
+    #[must_use]
     #[unstable(feature = "unix_socket_ancillary_data", issue = "76915")]
     pub fn is_empty(&self) -> bool {
         self.length == 0
     }
 
     /// Returns the number of used bytes.
+    #[must_use]
     #[unstable(feature = "unix_socket_ancillary_data", issue = "76915")]
     pub fn len(&self) -> usize {
         self.length
-- 
cgit 1.4.1-3-g733a5