constify more functions

Constify more functions, since we're raising the MSRV from 1.41.0 to
1.46.0.

Fixes #1477

4 files changed, 15 insertions, 14 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index c2037cb5..47cd139e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -44,6 +44,7 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 
 - Many more functions, mostly contructors, are now `const`.
   (#[1476](https://github.com/nix-rust/nix/pull/1476))
+  (#[1492](https://github.com/nix-rust/nix/pull/1492))
 
 - `sys::event::KEvent::filter` now returns a `Result` instead of being
   infalliable.  The only cases where it will now return an error are cases
diff --git a/src/errno.rs b/src/errno.rs
index 07c8944c..8e3a924b 100644
--- a/src/errno.rs
+++ b/src/errno.rs
@@ -93,7 +93,7 @@ impl Errno {
         desc(self)
     }
 
-    pub fn from_i32(err: i32) -> Errno {
+    pub const fn from_i32(err: i32) -> Errno {
         from_i32(err)
     }
 
@@ -928,7 +928,7 @@ mod consts {
         pub const ENOTSUP:     Errno = Errno::EOPNOTSUPP;
     }
 
-    pub fn from_i32(e: i32) -> Errno {
+    pub const fn from_i32(e: i32) -> Errno {
         use self::Errno::*;
 
         match e {
@@ -1207,7 +1207,7 @@ mod consts {
         pub const EDEADLOCK:   Errno = Errno::EDEADLK;
     }
 
-    pub fn from_i32(e: i32) -> Errno {
+    pub const fn from_i32(e: i32) -> Errno {
         use self::Errno::*;
 
         match e {
@@ -1455,7 +1455,7 @@ mod consts {
         pub const EOPNOTSUPP:  Errno = Errno::ENOTSUP;
     }
 
-    pub fn from_i32(e: i32) -> Errno {
+    pub const fn from_i32(e: i32) -> Errno {
         use self::Errno::*;
 
         match e {
@@ -1692,7 +1692,7 @@ mod consts {
         pub const EOPNOTSUPP:  Errno = Errno::ENOTSUP;
     }
 
-    pub fn from_i32(e: i32) -> Errno {
+    pub const fn from_i32(e: i32) -> Errno {
         use self::Errno::*;
 
         match e {
@@ -1916,7 +1916,7 @@ mod consts {
         pub const EWOULDBLOCK: Errno = Errno::EAGAIN;
     }
 
-    pub fn from_i32(e: i32) -> Errno {
+    pub const fn from_i32(e: i32) -> Errno {
         use self::Errno::*;
 
         match e {
@@ -2141,7 +2141,7 @@ mod consts {
         pub const EWOULDBLOCK: Errno = Errno::EAGAIN;
     }
 
-    pub fn from_i32(e: i32) -> Errno {
+    pub const fn from_i32(e: i32) -> Errno {
         use self::Errno::*;
 
         match e {
@@ -2350,7 +2350,7 @@ mod consts {
         pub const EWOULDBLOCK: Errno = Errno::EAGAIN;
     }
 
-    pub fn from_i32(e: i32) -> Errno {
+    pub const fn from_i32(e: i32) -> Errno {
         use self::Errno::*;
 
         match e {
@@ -2590,7 +2590,7 @@ mod consts {
         pub const EWOULDBLOCK: Errno = Errno::EAGAIN;
     }
 
-    pub fn from_i32(e: i32) -> Errno {
+    pub const fn from_i32(e: i32) -> Errno {
         use self::Errno::*;
 
         match e {
diff --git a/src/sys/signal.rs b/src/sys/signal.rs
index e68ebf16..95663687 100644
--- a/src/sys/signal.rs
+++ b/src/sys/signal.rs
@@ -133,7 +133,7 @@ impl Signal {
     /// This function is equivalent to `<Signal as AsRef<str>>::as_ref()`,
     /// with difference that returned string is `'static`
     /// and not bound to `self`'s lifetime.
-    pub fn as_str(self) -> &'static str {
+    pub const fn as_str(self) -> &'static str {
         match self {
             Signal::SIGHUP => "SIGHUP",
             Signal::SIGINT => "SIGINT",
diff --git a/src/sys/socket/addr.rs b/src/sys/socket/addr.rs
index 366c9afd..a964d61b 100644
--- a/src/sys/socket/addr.rs
+++ b/src/sys/socket/addr.rs
@@ -237,7 +237,7 @@ impl AddressFamily {
     ///
     /// Currently only supports these address families: Unix, Inet (v4 & v6), Netlink, Link/Packet
     /// and System. Returns None for unsupported or unknown address families.
-    pub fn from_i32(family: i32) -> Option<AddressFamily> {
+    pub const fn from_i32(family: i32) -> Option<AddressFamily> {
         match family {
             libc::AF_UNIX => Some(AddressFamily::Unix),
             libc::AF_INET => Some(AddressFamily::Inet),
@@ -314,7 +314,7 @@ impl InetAddr {
         }
     }
     /// Gets the IP address associated with this socket address.
-    pub fn ip(&self) -> IpAddr {
+    pub const fn ip(&self) -> IpAddr {
         match *self {
             InetAddr::V4(ref sa) => IpAddr::V4(Ipv4Addr(sa.sin_addr)),
             InetAddr::V6(ref sa) => IpAddr::V6(Ipv6Addr(sa.sin6_addr)),
@@ -322,7 +322,7 @@ impl InetAddr {
     }
 
     /// Gets the port number associated with this socket address
-    pub fn port(&self) -> u16 {
+    pub const fn port(&self) -> u16 {
         match *self {
             InetAddr::V6(ref sa) => u16::from_be(sa.sin6_port),
             InetAddr::V4(ref sa) => u16::from_be(sa.sin_port),
@@ -393,7 +393,7 @@ impl IpAddr {
         }
     }
 
-    pub fn to_std(&self) -> net::IpAddr {
+    pub const fn to_std(&self) -> net::IpAddr {
         match *self {
             IpAddr::V4(ref ip) => net::IpAddr::V4(ip.to_std()),
             IpAddr::V6(ref ip) => net::IpAddr::V6(ip.to_std()),