misc Clippy cleanup

* Fix race conditions in the tests.  Two tests were grabbing a mutex but
  immediately dropping it.  Thank you, Clippy.

* Remove vestigial Windows support.  Remove some code added to support
  Windows in 2015.  Nix is no longer intended to ever run on Windows.

* Various other minor Clippy lints.

8 files changed, 44 insertions, 52 deletions

diff --git a/src/errno.rs b/src/errno.rs
index 0e8839e6..9275febe 100644
--- a/src/errno.rs
+++ b/src/errno.rs
@@ -94,7 +94,7 @@ impl ErrnoSentinel for i64 {
 }
 
 impl ErrnoSentinel for *mut c_void {
-    fn sentinel() -> Self { (-1 as isize) as *mut c_void }
+    fn sentinel() -> Self { -1isize as *mut c_void }
 }
 
 impl ErrnoSentinel for libc::sighandler_t {
diff --git a/src/fcntl.rs b/src/fcntl.rs
index 2532724b..ce30b7d1 100644
--- a/src/fcntl.rs
+++ b/src/fcntl.rs
@@ -166,7 +166,7 @@ libc_bitflags!(
 );
 
 // The conversion is not identical on all operating systems.
-#[allow(clippy::identity_conversion)]
+#[allow(clippy::useless_conversion)]
 pub fn open<P: ?Sized + NixPath>(path: &P, oflag: OFlag, mode: Mode) -> Result<RawFd> {
     let fd = path.with_nix_path(|cstr| {
         unsafe { libc::open(cstr.as_ptr(), oflag.bits(), mode.bits() as c_uint) }
@@ -176,7 +176,7 @@ pub fn open<P: ?Sized + NixPath>(path: &P, oflag: OFlag, mode: Mode) -> Result<R
 }
 
 // The conversion is not identical on all operating systems.
-#[allow(clippy::identity_conversion)]
+#[allow(clippy::useless_conversion)]
 #[cfg(not(target_os = "redox"))]
 pub fn openat<P: ?Sized + NixPath>(
     dirfd: RawFd,
@@ -264,7 +264,7 @@ fn inner_readlink<P: ?Sized + NixPath>(dirfd: Option<RawFd>, path: &P) -> Result
         Some(dirfd) => super::sys::stat::fstatat(dirfd, path, AtFlags::AT_SYMLINK_NOFOLLOW),
         None => super::sys::stat::lstat(path)
     }
-        .and_then(|x| Ok(x.st_size))
+        .map(|x| x.st_size)
         .unwrap_or(0);
     let mut try_size = if reported_size > 0 {
         // Note: even if `lstat`'s apparently valid answer turns out to be
diff --git a/src/sys/aio.rs b/src/sys/aio.rs
index 7868a294..a03caa45 100644
--- a/src/sys/aio.rs
+++ b/src/sys/aio.rs
@@ -513,7 +513,7 @@ impl<'a> AioCb<'a> {
         }
     }
 
-    fn error_unpinned(self: &mut Self) -> Result<()> {
+    fn error_unpinned(&mut self) -> Result<()> {
         let r = unsafe {
             libc::aio_error(&mut self.aiocb.0 as *mut libc::aiocb)
         };
@@ -645,7 +645,7 @@ impl<'a> AioCb<'a> {
         SigEvent::from(&self.aiocb.0.aio_sigevent)
     }
 
-    fn aio_return_unpinned(self: &mut Self) -> Result<isize> {
+    fn aio_return_unpinned(&mut self) -> Result<isize> {
         unsafe {
             let p: *mut libc::aiocb = &mut self.aiocb.0;
             self.in_progress = false;
@@ -838,6 +838,10 @@ unsafe impl<'a> Sync for LioCb<'a> {}
 
 #[cfg(not(any(target_os = "ios", target_os = "macos")))]
 impl<'a> LioCb<'a> {
+    pub fn is_empty(&self) -> bool {
+        self.aiocbs.is_empty()
+    }
+
     /// Return the number of individual [`AioCb`]s contained.
     pub fn len(&self) -> usize {
         self.aiocbs.len()
diff --git a/src/sys/ptrace/bsd.rs b/src/sys/ptrace/bsd.rs
index e85afc76..141dfbc4 100644
--- a/src/sys/ptrace/bsd.rs
+++ b/src/sys/ptrace/bsd.rs
@@ -133,16 +133,14 @@ pub fn kill(pid: Pid) -> Result<()> {
 /// use nix::unistd::Pid;
 /// use nix::sys::signal::Signal;
 /// use nix::sys::wait::*;
-/// fn main() {
-///     // If a process changes state to the stopped state because of a SIGUSR1
-///     // signal, this will step the process forward and forward the user
-///     // signal to the stopped process
-///     match waitpid(Pid::from_raw(-1), None) {
-///         Ok(WaitStatus::Stopped(pid, Signal::SIGUSR1)) => {
-///             let _ = step(pid, Signal::SIGUSR1);
-///         }
-///         _ => {},
+/// // If a process changes state to the stopped state because of a SIGUSR1
+/// // signal, this will step the process forward and forward the user
+/// // signal to the stopped process
+/// match waitpid(Pid::from_raw(-1), None) {
+///     Ok(WaitStatus::Stopped(pid, Signal::SIGUSR1)) => {
+///         let _ = step(pid, Signal::SIGUSR1);
 ///     }
+///     _ => {},
 /// }
 /// ```
 #[cfg(
diff --git a/src/sys/select.rs b/src/sys/select.rs
index 19ae2f1c..5eb64234 100644
--- a/src/sys/select.rs
+++ b/src/sys/select.rs
@@ -50,12 +50,10 @@ impl FdSet {
     ///
     /// ```
     /// # use nix::sys::select::FdSet;
-    /// # fn main() {
     /// let mut set = FdSet::new();
     /// set.insert(4);
     /// set.insert(9);
     /// assert_eq!(set.highest(), Some(9));
-    /// # }
     /// ```
     ///
     /// [`select`]: fn.select.html
diff --git a/src/sys/socket/mod.rs b/src/sys/socket/mod.rs
index e4baeb5d..69070463 100644
--- a/src/sys/socket/mod.rs
+++ b/src/sys/socket/mod.rs
@@ -710,7 +710,7 @@ impl ControlMessageOwned {
             },
             (_, _) => {
                 let sl = slice::from_raw_parts(p, len);
-                let ucmsg = UnknownCmsg(*header, Vec::<u8>::from(&sl[..]));
+                let ucmsg = UnknownCmsg(*header, Vec::<u8>::from(sl));
                 ControlMessageOwned::Unknown(ucmsg)
             }
         }
diff --git a/src/time.rs b/src/time.rs
index e6c3f8de..f7da654a 100644
--- a/src/time.rs
+++ b/src/time.rs
@@ -185,9 +185,9 @@ impl ClockId {
     pub const CLOCK_VIRTUAL: ClockId = ClockId(libc::CLOCK_VIRTUAL);
 }
 
-impl Into<clockid_t> for ClockId {
-    fn into(self) -> clockid_t {
-        self.as_raw()
+impl From<ClockId> for clockid_t {
+    fn from(clock_id: ClockId) -> Self {
+        clock_id.as_raw()
     }
 }
 
diff --git a/src/unistd.rs b/src/unistd.rs
index 11907fa9..8e361bad 100644
--- a/src/unistd.rs
+++ b/src/unistd.rs
@@ -450,15 +450,13 @@ pub fn fchdir(dirfd: RawFd) -> Result<()> {
 /// use nix::sys::stat;
 /// use tempfile::tempdir;
 ///
-/// fn main() {
-///     let tmp_dir1 = tempdir().unwrap();
-///     let tmp_dir2 = tmp_dir1.path().join("new_dir");
-///
-///     // create new directory and give read, write and execute rights to the owner
-///     match unistd::mkdir(&tmp_dir2, stat::Mode::S_IRWXU) {
-///        Ok(_) => println!("created {:?}", tmp_dir2),
-///        Err(err) => println!("Error creating directory: {}", err),
-///     }
+/// let tmp_dir1 = tempdir().unwrap();
+/// let tmp_dir2 = tmp_dir1.path().join("new_dir");
+///
+/// // create new directory and give read, write and execute rights to the owner
+/// match unistd::mkdir(&tmp_dir2, stat::Mode::S_IRWXU) {
+///    Ok(_) => println!("created {:?}", tmp_dir2),
+///    Err(err) => println!("Error creating directory: {}", err),
 /// }
 /// ```
 #[inline]
@@ -490,15 +488,13 @@ pub fn mkdir<P: ?Sized + NixPath>(path: &P, mode: Mode) -> Result<()> {
 /// use nix::sys::stat;
 /// use tempfile::tempdir;
 ///
-/// fn main() {
-///     let tmp_dir = tempdir().unwrap();
-///     let fifo_path = tmp_dir.path().join("foo.pipe");
+/// let tmp_dir = tempdir().unwrap();
+/// let fifo_path = tmp_dir.path().join("foo.pipe");
 ///
-///     // create new fifo and give read, write and execute rights to the owner
-///     match unistd::mkfifo(&fifo_path, stat::Mode::S_IRWXU) {
-///        Ok(_) => println!("created {:?}", fifo_path),
-///        Err(err) => println!("Error creating fifo: {}", err),
-///     }
+/// // create new fifo and give read, write and execute rights to the owner
+/// match unistd::mkfifo(&fifo_path, stat::Mode::S_IRWXU) {
+///    Ok(_) => println!("created {:?}", fifo_path),
+///    Err(err) => println!("Error creating fifo: {}", err),
 /// }
 /// ```
 #[inline]
@@ -587,11 +583,9 @@ fn reserve_double_buffer_size<T>(buf: &mut Vec<T>, limit: usize) -> Result<()> {
 /// ```rust
 /// use nix::unistd;
 ///
-/// fn main() {
-///     // assume that we are allowed to get current directory
-///     let dir = unistd::getcwd().unwrap();
-///     println!("The current directory is {:?}", dir);
-/// }
+/// // assume that we are allowed to get current directory
+/// let dir = unistd::getcwd().unwrap();
+/// println!("The current directory is {:?}", dir);
 /// ```
 #[inline]
 pub fn getcwd() -> Result<PathBuf> {
@@ -624,6 +618,8 @@ pub fn getcwd() -> Result<PathBuf> {
 }
 
 /// Computes the raw UID and GID values to pass to a `*chown` call.
+// The cast is not unnecessary on all platforms.
+#[allow(clippy::unnecessary_cast)]
 fn chown_raw_ids(owner: Option<Uid>, group: Option<Gid>) -> (libc::uid_t, libc::gid_t) {
     // According to the POSIX specification, -1 is used to indicate that owner and group
     // are not to be changed.  Since uid_t and gid_t are unsigned types, we have to wrap
@@ -969,20 +965,16 @@ pub fn gethostname(buffer: &mut [u8]) -> Result<&CStr> {
 /// use std::os::unix::io::AsRawFd;
 /// use nix::unistd::close;
 ///
-/// fn main() {
-///     let f = tempfile::tempfile().unwrap();
-///     close(f.as_raw_fd()).unwrap();   // Bad!  f will also close on drop!
-/// }
+/// let f = tempfile::tempfile().unwrap();
+/// close(f.as_raw_fd()).unwrap();   // Bad!  f will also close on drop!
 /// ```
 ///
 /// ```rust
 /// use std::os::unix::io::IntoRawFd;
 /// use nix::unistd::close;
 ///
-/// fn main() {
-///     let f = tempfile::tempfile().unwrap();
-///     close(f.into_raw_fd()).unwrap(); // Good.  into_raw_fd consumes f
-/// }
+/// let f = tempfile::tempfile().unwrap();
+/// close(f.into_raw_fd()).unwrap(); // Good.  into_raw_fd consumes f
 /// ```
 pub fn close(fd: RawFd) -> Result<()> {
     let res = unsafe { libc::close(fd) };
@@ -1563,7 +1555,7 @@ pub fn getgrouplist(user: &CStr, group: Gid) -> Result<Vec<Gid>> {
             // groups as possible, but Linux manpages do not mention this
             // behavior.
             reserve_double_buffer_size(&mut groups, ngroups_max as usize)
-                .or_else(|_| Err(Error::invalid_argument()))?;
+                .map_err(|_| Error::invalid_argument())?;
         }
     }
 }