diff --git a/library/std/src/fs.rs b/library/std/src/fs.rs
index 85d35072923..9f45e89aa75 100644
--- a/library/std/src/fs.rs
+++ b/library/std/src/fs.rs
@@ -1005,6 +1005,7 @@ impl Metadata {
     ///     Ok(())
     /// }
     /// ```
+    #[must_use]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn is_dir(&self) -> bool {
         self.file_type().is_dir()
@@ -1033,6 +1034,7 @@ impl Metadata {
     ///     Ok(())
     /// }
     /// ```
+    #[must_use]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn is_file(&self) -> bool {
         self.file_type().is_file()
@@ -1059,6 +1061,7 @@ impl Metadata {
     ///     Ok(())
     /// }
     /// ```
+    #[must_use]
     #[unstable(feature = "is_symlink", issue = "85748")]
     pub fn is_symlink(&self) -> bool {
         self.file_type().is_symlink()
@@ -1306,6 +1309,7 @@ impl FileType {
     ///     Ok(())
     /// }
     /// ```
+    #[must_use]
     #[stable(feature = "file_type", since = "1.1.0")]
     pub fn is_dir(&self) -> bool {
         self.0.is_dir()
@@ -1338,6 +1342,7 @@ impl FileType {
     ///     Ok(())
     /// }
     /// ```
+    #[must_use]
     #[stable(feature = "file_type", since = "1.1.0")]
     pub fn is_file(&self) -> bool {
         self.0.is_file()
@@ -1373,6 +1378,7 @@ impl FileType {
     ///     Ok(())
     /// }
     /// ```
+    #[must_use]
     #[stable(feature = "file_type", since = "1.1.0")]
     pub fn is_symlink(&self) -> bool {
         self.0.is_symlink()
diff --git a/library/std/src/net/addr.rs b/library/std/src/net/addr.rs
index cd2007cc2cb..a689d2a56b7 100644
--- a/library/std/src/net/addr.rs
+++ b/library/std/src/net/addr.rs
@@ -232,6 +232,7 @@ impl SocketAddr {
     /// assert_eq!(socket.is_ipv4(), true);
     /// assert_eq!(socket.is_ipv6(), false);
     /// ```
+    #[must_use]
     #[stable(feature = "sockaddr_checker", since = "1.16.0")]
     #[rustc_const_unstable(feature = "const_socketaddr", issue = "82485")]
     pub const fn is_ipv4(&self) -> bool {
@@ -253,6 +254,7 @@ impl SocketAddr {
     /// assert_eq!(socket.is_ipv4(), false);
     /// assert_eq!(socket.is_ipv6(), true);
     /// ```
+    #[must_use]
     #[stable(feature = "sockaddr_checker", since = "1.16.0")]
     #[rustc_const_unstable(feature = "const_socketaddr", issue = "82485")]
     pub const fn is_ipv6(&self) -> bool {
diff --git a/library/std/src/net/ip.rs b/library/std/src/net/ip.rs
index 99922eef61f..68b8bb8f3e1 100644
--- a/library/std/src/net/ip.rs
+++ b/library/std/src/net/ip.rs
@@ -233,6 +233,7 @@ impl IpAddr {
     /// ```
     #[rustc_const_stable(feature = "const_ip", since = "1.50.0")]
     #[stable(feature = "ip_shared", since = "1.12.0")]
+    #[must_use]
     #[inline]
     pub const fn is_unspecified(&self) -> bool {
         match self {
@@ -256,6 +257,7 @@ impl IpAddr {
     /// ```
     #[rustc_const_stable(feature = "const_ip", since = "1.50.0")]
     #[stable(feature = "ip_shared", since = "1.12.0")]
+    #[must_use]
     #[inline]
     pub const fn is_loopback(&self) -> bool {
         match self {
@@ -281,6 +283,7 @@ impl IpAddr {
     /// ```
     #[rustc_const_unstable(feature = "const_ip", issue = "76205")]
     #[unstable(feature = "ip", issue = "27709")]
+    #[must_use]
     #[inline]
     pub const fn is_global(&self) -> bool {
         match self {
@@ -304,6 +307,7 @@ impl IpAddr {
     /// ```
     #[rustc_const_stable(feature = "const_ip", since = "1.50.0")]
     #[stable(feature = "ip_shared", since = "1.12.0")]
+    #[must_use]
     #[inline]
     pub const fn is_multicast(&self) -> bool {
         match self {
@@ -332,6 +336,7 @@ impl IpAddr {
     /// ```
     #[rustc_const_unstable(feature = "const_ip", issue = "76205")]
     #[unstable(feature = "ip", issue = "27709")]
+    #[must_use]
     #[inline]
     pub const fn is_documentation(&self) -> bool {
         match self {
@@ -356,6 +361,7 @@ impl IpAddr {
     /// assert_eq!(IpAddr::V6(Ipv6Addr::new(0x2001, 0x2, 0, 0, 0, 0, 0, 0)).is_benchmarking(), true);
     /// ```
     #[unstable(feature = "ip", issue = "27709")]
+    #[must_use]
     #[inline]
     pub const fn is_benchmarking(&self) -> bool {
         match self {
@@ -379,6 +385,7 @@ impl IpAddr {
     /// ```
     #[rustc_const_stable(feature = "const_ip", since = "1.50.0")]
     #[stable(feature = "ipaddr_checker", since = "1.16.0")]
+    #[must_use]
     #[inline]
     pub const fn is_ipv4(&self) -> bool {
         matches!(self, IpAddr::V4(_))
@@ -399,6 +406,7 @@ impl IpAddr {
     /// ```
     #[rustc_const_stable(feature = "const_ip", since = "1.50.0")]
     #[stable(feature = "ipaddr_checker", since = "1.16.0")]
+    #[must_use]
     #[inline]
     pub const fn is_ipv6(&self) -> bool {
         matches!(self, IpAddr::V6(_))
@@ -527,6 +535,7 @@ impl Ipv4Addr {
     /// ```
     #[rustc_const_stable(feature = "const_ipv4", since = "1.32.0")]
     #[stable(feature = "ip_shared", since = "1.12.0")]
+    #[must_use]
     #[inline]
     pub const fn is_unspecified(&self) -> bool {
         self.inner.s_addr == 0
@@ -548,6 +557,7 @@ impl Ipv4Addr {
     /// ```
     #[rustc_const_stable(feature = "const_ipv4", since = "1.50.0")]
     #[stable(since = "1.7.0", feature = "ip_17")]
+    #[must_use]
     #[inline]
     pub const fn is_loopback(&self) -> bool {
         self.octets()[0] == 127
@@ -578,6 +588,7 @@ impl Ipv4Addr {
     /// ```
     #[rustc_const_stable(feature = "const_ipv4", since = "1.50.0")]
     #[stable(since = "1.7.0", feature = "ip_17")]
+    #[must_use]
     #[inline]
     pub const fn is_private(&self) -> bool {
         match self.octets() {
@@ -605,6 +616,7 @@ impl Ipv4Addr {
     /// ```
     #[rustc_const_stable(feature = "const_ipv4", since = "1.50.0")]
     #[stable(since = "1.7.0", feature = "ip_17")]
+    #[must_use]
     #[inline]
     pub const fn is_link_local(&self) -> bool {
         matches!(self.octets(), [169, 254, ..])
@@ -680,6 +692,7 @@ impl Ipv4Addr {
     /// ```
     #[rustc_const_unstable(feature = "const_ipv4", issue = "76205")]
     #[unstable(feature = "ip", issue = "27709")]
+    #[must_use]
     #[inline]
     pub const fn is_global(&self) -> bool {
         // check if this address is 192.0.0.9 or 192.0.0.10. These addresses are the only two
@@ -720,6 +733,7 @@ impl Ipv4Addr {
     /// ```
     #[rustc_const_unstable(feature = "const_ipv4", issue = "76205")]
     #[unstable(feature = "ip", issue = "27709")]
+    #[must_use]
     #[inline]
     pub const fn is_shared(&self) -> bool {
         self.octets()[0] == 100 && (self.octets()[1] & 0b1100_0000 == 0b0100_0000)
@@ -745,6 +759,7 @@ impl Ipv4Addr {
     /// ```
     #[rustc_const_unstable(feature = "const_ipv4", issue = "76205")]
     #[unstable(feature = "ip", issue = "27709")]
+    #[must_use]
     #[inline]
     pub const fn is_benchmarking(&self) -> bool {
         self.octets()[0] == 198 && (self.octets()[1] & 0xfe) == 18
@@ -779,6 +794,7 @@ impl Ipv4Addr {
     /// ```
     #[rustc_const_unstable(feature = "const_ipv4", issue = "76205")]
     #[unstable(feature = "ip", issue = "27709")]
+    #[must_use]
     #[inline]
     pub const fn is_reserved(&self) -> bool {
         self.octets()[0] & 240 == 240 && !self.is_broadcast()
@@ -802,6 +818,7 @@ impl Ipv4Addr {
     /// ```
     #[rustc_const_stable(feature = "const_ipv4", since = "1.50.0")]
     #[stable(since = "1.7.0", feature = "ip_17")]
+    #[must_use]
     #[inline]
     pub const fn is_multicast(&self) -> bool {
         self.octets()[0] >= 224 && self.octets()[0] <= 239
@@ -823,6 +840,7 @@ impl Ipv4Addr {
     /// ```
     #[rustc_const_stable(feature = "const_ipv4", since = "1.50.0")]
     #[stable(since = "1.7.0", feature = "ip_17")]
+    #[must_use]
     #[inline]
     pub const fn is_broadcast(&self) -> bool {
         u32::from_be_bytes(self.octets()) == u32::from_be_bytes(Self::BROADCAST.octets())
@@ -850,6 +868,7 @@ impl Ipv4Addr {
     /// ```
     #[rustc_const_stable(feature = "const_ipv4", since = "1.50.0")]
     #[stable(since = "1.7.0", feature = "ip_17")]
+    #[must_use]
     #[inline]
     pub const fn is_documentation(&self) -> bool {
         match self.octets() {
@@ -1291,6 +1310,7 @@ impl Ipv6Addr {
     /// ```
     #[rustc_const_stable(feature = "const_ipv6", since = "1.50.0")]
     #[stable(since = "1.7.0", feature = "ip_17")]
+    #[must_use]
     #[inline]
     pub const fn is_unspecified(&self) -> bool {
         u128::from_be_bytes(self.octets()) == u128::from_be_bytes(Ipv6Addr::UNSPECIFIED.octets())
@@ -1314,6 +1334,7 @@ impl Ipv6Addr {
     /// ```
     #[rustc_const_stable(feature = "const_ipv6", since = "1.50.0")]
     #[stable(since = "1.7.0", feature = "ip_17")]
+    #[must_use]
     #[inline]
     pub const fn is_loopback(&self) -> bool {
         u128::from_be_bytes(self.octets()) == u128::from_be_bytes(Ipv6Addr::LOCALHOST.octets())
@@ -1340,6 +1361,7 @@ impl Ipv6Addr {
     /// ```
     #[rustc_const_unstable(feature = "const_ipv6", issue = "76205")]
     #[unstable(feature = "ip", issue = "27709")]
+    #[must_use]
     #[inline]
     pub const fn is_global(&self) -> bool {
         match self.multicast_scope() {
@@ -1367,6 +1389,7 @@ impl Ipv6Addr {
     /// ```
     #[rustc_const_unstable(feature = "const_ipv6", issue = "76205")]
     #[unstable(feature = "ip", issue = "27709")]
+    #[must_use]
     #[inline]
     pub const fn is_unique_local(&self) -> bool {
         (self.segments()[0] & 0xfe00) == 0xfc00
@@ -1395,6 +1418,7 @@ impl Ipv6Addr {
     /// ```
     #[rustc_const_unstable(feature = "const_ipv6", issue = "76205")]
     #[unstable(feature = "ip", issue = "27709")]
+    #[must_use]
     #[inline]
     pub const fn is_unicast(&self) -> bool {
         !self.is_multicast()
@@ -1446,6 +1470,7 @@ impl Ipv6Addr {
     /// ```
     #[rustc_const_unstable(feature = "const_ipv6", issue = "76205")]
     #[unstable(feature = "ip", issue = "27709")]
+    #[must_use]
     #[inline]
     pub const fn is_unicast_link_local(&self) -> bool {
         (self.segments()[0] & 0xffc0) == 0xfe80
@@ -1470,6 +1495,7 @@ impl Ipv6Addr {
     /// ```
     #[rustc_const_unstable(feature = "const_ipv6", issue = "76205")]
     #[unstable(feature = "ip", issue = "27709")]
+    #[must_use]
     #[inline]
     pub const fn is_documentation(&self) -> bool {
         (self.segments()[0] == 0x2001) && (self.segments()[1] == 0xdb8)
@@ -1492,6 +1518,7 @@ impl Ipv6Addr {
     /// assert_eq!(Ipv6Addr::new(0x2001, 0x2, 0, 0, 0, 0, 0, 0).is_benchmarking(), true);
     /// ```
     #[unstable(feature = "ip", issue = "27709")]
+    #[must_use]
     #[inline]
     pub const fn is_benchmarking(&self) -> bool {
         (self.segments()[0] == 0x2001) && (self.segments()[1] == 0x2) && (self.segments()[2] == 0)
@@ -1529,6 +1556,7 @@ impl Ipv6Addr {
     /// ```
     #[rustc_const_unstable(feature = "const_ipv6", issue = "76205")]
     #[unstable(feature = "ip", issue = "27709")]
+    #[must_use]
     #[inline]
     pub const fn is_unicast_global(&self) -> bool {
         self.is_unicast()
@@ -1590,6 +1618,7 @@ impl Ipv6Addr {
     /// ```
     #[rustc_const_stable(feature = "const_ipv6", since = "1.50.0")]
     #[stable(since = "1.7.0", feature = "ip_17")]
+    #[must_use]
     #[inline]
     pub const fn is_multicast(&self) -> bool {
         (self.segments()[0] & 0xff00) == 0xff00
diff --git a/library/std/src/os/unix/net/addr.rs b/library/std/src/os/unix/net/addr.rs
index 62bfde8bfd4..9b2eb793dfd 100644
--- a/library/std/src/os/unix/net/addr.rs
+++ b/library/std/src/os/unix/net/addr.rs
@@ -156,6 +156,7 @@ impl SocketAddr {
     ///     Ok(())
     /// }
     /// ```
+    #[must_use]
     #[stable(feature = "unix_socket", since = "1.10.0")]
     pub fn is_unnamed(&self) -> bool {
         if let AddressKind::Unnamed = self.address() { true } else { false }
diff --git a/library/std/src/path.rs b/library/std/src/path.rs
index a8a79fb9c8f..d3c31b006ba 100644
--- a/library/std/src/path.rs
+++ b/library/std/src/path.rs
@@ -215,6 +215,7 @@ impl<'a> Prefix<'a> {
     /// assert!(!Disk(b'C').is_verbatim());
     /// ```
     #[inline]
+    #[must_use]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn is_verbatim(&self) -> bool {
         use self::Prefix::*;
@@ -247,6 +248,7 @@ impl<'a> Prefix<'a> {
 /// assert!(path::is_separator('/')); // '/' works for both Unix and Windows
 /// assert!(!path::is_separator('❤'));
 /// ```
+#[must_use]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub fn is_separator(c: char) -> bool {
     c.is_ascii() && is_sep_byte(c as u8)
@@ -2011,6 +2013,7 @@ impl Path {
     ///
     /// [`has_root`]: Path::has_root
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[must_use]
     #[allow(deprecated)]
     pub fn is_absolute(&self) -> bool {
         if cfg!(target_os = "redox") {
@@ -2035,6 +2038,7 @@ impl Path {
     ///
     /// [`is_absolute`]: Path::is_absolute
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[must_use]
     #[inline]
     pub fn is_relative(&self) -> bool {
         !self.is_absolute()
@@ -2061,6 +2065,7 @@ impl Path {
     /// assert!(Path::new("/etc/passwd").has_root());
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[must_use]
     #[inline]
     pub fn has_root(&self) -> bool {
         self.components().has_root()
@@ -2698,6 +2703,7 @@ impl Path {
     /// a Unix-like system for example. See [`fs::File::open`] or
     /// [`fs::OpenOptions::open`] for more information.
     #[stable(feature = "path_ext", since = "1.5.0")]
+    #[must_use]
     pub fn is_file(&self) -> bool {
         fs::metadata(self).map(|m| m.is_file()).unwrap_or(false)
     }
@@ -2724,6 +2730,7 @@ impl Path {
     /// check errors, call [`fs::metadata`] and handle its [`Result`]. Then call
     /// [`fs::Metadata::is_dir`] if it was [`Ok`].
     #[stable(feature = "path_ext", since = "1.5.0")]
+    #[must_use]
     pub fn is_dir(&self) -> bool {
         fs::metadata(self).map(|m| m.is_dir()).unwrap_or(false)
     }
@@ -2750,6 +2757,7 @@ impl Path {
     /// assert_eq!(link_path.exists(), false);
     /// ```
     #[unstable(feature = "is_symlink", issue = "85748")]
+    #[must_use]
     pub fn is_symlink(&self) -> bool {
         fs::symlink_metadata(self).map(|m| m.is_symlink()).unwrap_or(false)
     }
diff --git a/library/std/src/sync/barrier.rs b/library/std/src/sync/barrier.rs
index 0e28a2d166f..133c3e46cd8 100644
--- a/library/std/src/sync/barrier.rs
+++ b/library/std/src/sync/barrier.rs
@@ -167,6 +167,7 @@ impl BarrierWaitResult {
     /// println!("{:?}", barrier_wait_result.is_leader());
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[must_use]
     pub fn is_leader(&self) -> bool {
         self.0
     }