signal: make SignalKind methods const (#4956)

tokio/src/signal/unix.rs

@@ -84,7 +84,7 @@ impl SignalKind {
     // unlikely to change to other types, but technically libc can change this
     // in the future minor version.
     // See https://github.com/tokio-rs/tokio/issues/3767 for more.
-    pub fn from_raw(signum: std::os::raw::c_int) -> Self {
+    pub const fn from_raw(signum: std::os::raw::c_int) -> Self {
         Self(signum as libc::c_int)
     }
 
@@ -95,31 +95,31 @@ impl SignalKind {
     /// let kind = SignalKind::interrupt();
     /// assert_eq!(kind.as_raw_value(), libc::SIGINT);
     /// ```
-    pub fn as_raw_value(&self) -> std::os::raw::c_int {
+    pub const fn as_raw_value(&self) -> std::os::raw::c_int {
         self.0
     }
 
     /// Represents the SIGALRM signal.
     ///
     /// On Unix systems this signal is sent when a real-time timer has expired.
     /// By default, the process is terminated by this signal.
-    pub fn alarm() -> Self {
+    pub const fn alarm() -> Self {
         Self(libc::SIGALRM)
     }
 
     /// Represents the SIGCHLD signal.
     ///
     /// On Unix systems this signal is sent when the status of a child process
     /// has changed. By default, this signal is ignored.
-    pub fn child() -> Self {
+    pub const fn child() -> Self {
         Self(libc::SIGCHLD)
     }
 
     /// Represents the SIGHUP signal.
     ///
     /// On Unix systems this signal is sent when the terminal is disconnected.
     /// By default, the process is terminated by this signal.
-    pub fn hangup() -> Self {
+    pub const fn hangup() -> Self {
         Self(libc::SIGHUP)
     }
 
@@ -134,23 +134,23 @@ impl SignalKind {
         target_os = "netbsd",
         target_os = "openbsd"
     ))]
-    pub fn info() -> Self {
+    pub const fn info() -> Self {
         Self(libc::SIGINFO)
     }
 
     /// Represents the SIGINT signal.
     ///
     /// On Unix systems this signal is sent to interrupt a program.
     /// By default, the process is terminated by this signal.
-    pub fn interrupt() -> Self {
+    pub const fn interrupt() -> Self {
         Self(libc::SIGINT)
     }
 
     /// Represents the SIGIO signal.
     ///
     /// On Unix systems this signal is sent when I/O operations are possible
     /// on some file descriptor. By default, this signal is ignored.
-    pub fn io() -> Self {
+    pub const fn io() -> Self {
         Self(libc::SIGIO)
     }
 
@@ -159,7 +159,7 @@ impl SignalKind {
     /// On Unix systems this signal is sent when the process attempts to write
     /// to a pipe which has no reader. By default, the process is terminated by
     /// this signal.
-    pub fn pipe() -> Self {
+    pub const fn pipe() -> Self {
         Self(libc::SIGPIPE)
     }
 
@@ -168,39 +168,39 @@ impl SignalKind {
     /// On Unix systems this signal is sent to issue a shutdown of the
     /// process, after which the OS will dump the process core.
     /// By default, the process is terminated by this signal.
-    pub fn quit() -> Self {
+    pub const fn quit() -> Self {
         Self(libc::SIGQUIT)
     }
 
     /// Represents the SIGTERM signal.
     ///
     /// On Unix systems this signal is sent to issue a shutdown of the
     /// process. By default, the process is terminated by this signal.
-    pub fn terminate() -> Self {
+    pub const fn terminate() -> Self {
         Self(libc::SIGTERM)
     }
 
     /// Represents the SIGUSR1 signal.
     ///
     /// On Unix systems this is a user defined signal.
     /// By default, the process is terminated by this signal.
-    pub fn user_defined1() -> Self {
+    pub const fn user_defined1() -> Self {
         Self(libc::SIGUSR1)
     }
 
     /// Represents the SIGUSR2 signal.
     ///
     /// On Unix systems this is a user defined signal.
     /// By default, the process is terminated by this signal.
-    pub fn user_defined2() -> Self {
+    pub const fn user_defined2() -> Self {
         Self(libc::SIGUSR2)
     }
 
     /// Represents the SIGWINCH signal.
     ///
     /// On Unix systems this signal is sent when the terminal window is resized.
     /// By default, this signal is ignored.
-    pub fn window_change() -> Self {
+    pub const fn window_change() -> Self {
         Self(libc::SIGWINCH)
     }
 }