Clippy cleanup

And this time, start running Clippy in CI

41 files changed, 154 insertions, 189 deletions

diff --git a/.cirrus.yml b/.cirrus.yml
index 515b1c97..c3d87611 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -18,6 +18,7 @@ build: &BUILD
     - . $HOME/.cargo/env || true
     - $TOOL +$TOOLCHAIN $BUILD $ZFLAGS --target $TARGET --all-targets
     - $TOOL +$TOOLCHAIN doc $ZFLAGS --no-deps --target $TARGET
+    - $TOOL +$TOOLCHAIN clippy $ZFLAGS --target $TARGET -- -D warnings
 
 # Tests that do require executing the binaries
 test: &TEST
@@ -39,7 +40,9 @@ task:
   setup_script:
     - fetch https://sh.rustup.rs -o rustup.sh
     - sh rustup.sh -y --profile=minimal --default-toolchain $TOOLCHAIN
-    - $HOME/.cargo/bin/rustup target add i686-unknown-freebsd
+    - . $HOME/.cargo/env
+    - rustup target add i686-unknown-freebsd
+    - rustup component add --toolchain $TOOLCHAIN clippy
   << : *TEST
   i386_test_script:
     - . $HOME/.cargo/env
@@ -60,6 +63,7 @@ task:
     - curl --proto '=https' --tlsv1.2 -sSf -o rustup.sh https://sh.rustup.rs
     - sh rustup.sh -y --profile=minimal --default-toolchain $TOOLCHAIN
     - . $HOME/.cargo/env
+    - rustup component add --toolchain $TOOLCHAIN clippy
   << : *TEST
   before_cache_script: rm -rf $CARGO_HOME/registry/index
 
@@ -142,6 +146,7 @@ task:
         TARGET: x86_64-unknown-linux-musl
   setup_script:
     - rustup target add $TARGET
+    - rustup component add clippy
   << : *TEST
   before_cache_script: rm -rf $CARGO_HOME/registry/index
 
@@ -224,6 +229,7 @@ task:
   setup_script:
     - rustup target add $TARGET
     - rustup toolchain install $TOOLCHAIN --profile minimal --target $TARGET
+    - rustup component add --toolchain $TOOLCHAIN clippy
   << : *BUILD
   before_cache_script: rm -rf $CARGO_HOME/registry/index
 
diff --git a/src/dir.rs b/src/dir.rs
index 65ed2e9d..ed70a458 100644
--- a/src/dir.rs
+++ b/src/dir.rs
@@ -84,7 +84,7 @@ impl AsRawFd for Dir {
 impl Drop for Dir {
     fn drop(&mut self) {
         let e = Errno::result(unsafe { libc::closedir(self.0.as_ptr()) });
-        if !std::thread::panicking() && e == Err(Error::from(Errno::EBADF)) {
+        if !std::thread::panicking() && e == Err(Errno::EBADF) {
             panic!("Closing an invalid file descriptor!");
         };
     }
@@ -211,6 +211,7 @@ impl Entry {
                   target_os = "linux",
                   target_os = "macos",
                   target_os = "solaris")))]
+    #[allow(clippy::useless_conversion)]    // Not useless on all OSes
     pub fn ino(&self) -> u64 {
         u64::from(self.0.d_fileno)
     }
diff --git a/src/errno.rs b/src/errno.rs
index 2be3179c..3da246e8 100644
--- a/src/errno.rs
+++ b/src/errno.rs
@@ -72,8 +72,9 @@ impl Errno {
         since = "0.22.0",
         note = "It's a no-op now; just delete it."
     )]
+    #[allow(clippy::wrong_self_convention)] // False positive
     pub fn from_errno(errno: Errno) -> Error {
-        Error::from(errno)
+        errno
     }
 
     /// Create a new invalid argument error (`EINVAL`)
diff --git a/src/fcntl.rs b/src/fcntl.rs
index 0a50e748..aded27b4 100644
--- a/src/fcntl.rs
+++ b/src/fcntl.rs
@@ -325,7 +325,7 @@ fn inner_readlink<P: ?Sized + NixPath>(dirfd: Option<RawFd>, path: &P) -> Result
                 Some(next_size) => try_size = next_size,
                 // It's absurd that this would happen, but handle it sanely
                 // anyway.
-                None => break Err(super::Error::from(Errno::ENAMETOOLONG)),
+                None => break Err(Errno::ENAMETOOLONG),
             }
         }
     }
@@ -646,7 +646,6 @@ pub fn fallocate(
 ))]
 mod posix_fadvise {
     use crate::errno::Errno;
-    use libc;
     use std::os::unix::io::RawFd;
     use crate::Result;
 
@@ -687,6 +686,6 @@ pub fn posix_fallocate(fd: RawFd, offset: libc::off_t, len: libc::off_t) -> Resu
     match Errno::result(res) {
         Err(err) => Err(err),
         Ok(0) => Ok(()),
-        Ok(errno) => Err(crate::Error::from(Errno::from_i32(errno))),
+        Ok(errno) => Err(Errno::from_i32(errno)),
     }
 }
diff --git a/src/kmod.rs b/src/kmod.rs
index 89e577a7..c42068c7 100644
--- a/src/kmod.rs
+++ b/src/kmod.rs
@@ -2,7 +2,6 @@
 //!
 //! For more details see
 
-use libc;
 use std::ffi::CStr;
 use std::os::unix::io::AsRawFd;
 
diff --git a/src/lib.rs b/src/lib.rs
index 7a64b97a..3a2b63ab 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -160,7 +160,7 @@ impl NixPath for CStr {
             where F: FnOnce(&CStr) -> T {
         // Equivalence with the [u8] impl.
         if self.len() >= PATH_MAX as usize {
-            return Err(Error::from(Errno::ENAMETOOLONG))
+            return Err(Errno::ENAMETOOLONG)
         }
 
         Ok(f(self))
@@ -181,11 +181,11 @@ impl NixPath for [u8] {
         let mut buf = [0u8; PATH_MAX as usize];
 
         if self.len() >= PATH_MAX as usize {
-            return Err(Error::from(Errno::ENAMETOOLONG))
+            return Err(Errno::ENAMETOOLONG)
         }
 
         match self.iter().position(|b| *b == 0) {
-            Some(_) => Err(Error::from(Errno::EINVAL)),
+            Some(_) => Err(Errno::EINVAL),
             None => {
                 unsafe {
                     // TODO: Replace with bytes::copy_memory. rust-lang/rust#24028
diff --git a/src/mount/bsd.rs b/src/mount/bsd.rs
index 9913fc20..23331a0a 100644
--- a/src/mount/bsd.rs
+++ b/src/mount/bsd.rs
@@ -383,7 +383,7 @@ impl<'a> Nmount<'a> {
                         Some(CStr::from_bytes_with_nul(sl).unwrap())
                     }
                 };
-                Err(NmountError::new(error.into(), errmsg))
+                Err(NmountError::new(error, errmsg))
             }
         }
     }
diff --git a/src/mount/linux.rs b/src/mount/linux.rs
index edb8afbd..4cb2fa54 100644
--- a/src/mount/linux.rs
+++ b/src/mount/linux.rs
@@ -1,3 +1,4 @@
+#![allow(missing_docs)]
 use libc::{self, c_ulong, c_int};
 use crate::{Result, NixPath};
 use crate::errno::Errno;
diff --git a/src/mount/mod.rs b/src/mount/mod.rs
index 00303b6a..14bf2a96 100644
--- a/src/mount/mod.rs
+++ b/src/mount/mod.rs
@@ -1,10 +1,8 @@
 //! Mount file systems
 #[cfg(any(target_os = "android", target_os = "linux"))]
-#[allow(missing_docs)]
 mod linux;
 
 #[cfg(any(target_os = "android", target_os = "linux"))]
-#[allow(missing_docs)]
 pub use self::linux::*;
 
 #[cfg(any(target_os = "dragonfly",
diff --git a/src/mqueue.rs b/src/mqueue.rs
index 8598eaf2..34fd8027 100644
--- a/src/mqueue.rs
+++ b/src/mqueue.rs
@@ -155,6 +155,7 @@ pub fn mq_setattr(mqd: mqd_t, newattr: &MqAttr) -> Result<MqAttr> {
 /// Convenience function.
 /// Sets the `O_NONBLOCK` attribute for a given message queue descriptor
 /// Returns the old attributes
+#[allow(clippy::useless_conversion)]    // Not useless on all OSes
 pub fn mq_set_nonblock(mqd: mqd_t) -> Result<MqAttr> {
     let oldattr = mq_getattr(mqd)?;
     let newattr = MqAttr::new(mq_attr_member_t::from(MQ_OFlag::O_NONBLOCK.bits()),
diff --git a/src/pty.rs b/src/pty.rs
index a8eb938d..facc9aaf 100644
--- a/src/pty.rs
+++ b/src/pty.rs
@@ -10,7 +10,7 @@ use std::os::unix::prelude::*;
 
 use crate::sys::termios::Termios;
 use crate::unistd::{self, ForkResult, Pid};
-use crate::{Result, Error, fcntl};
+use crate::{Result, fcntl};
 use crate::errno::Errno;
 
 /// Representation of a master/slave pty pair
@@ -99,7 +99,7 @@ impl io::Write for PtyMaster {
 #[inline]
 pub fn grantpt(fd: &PtyMaster) -> Result<()> {
     if unsafe { libc::grantpt(fd.as_raw_fd()) } < 0 {
-        return Err(Error::from(Errno::last()));
+        return Err(Errno::last());
     }
 
     Ok(())
@@ -145,7 +145,7 @@ pub fn posix_openpt(flags: fcntl::OFlag) -> Result<PtyMaster> {
     };
 
     if fd < 0 {
-        return Err(Error::from(Errno::last()));
+        return Err(Errno::last());
     }
 
     Ok(PtyMaster(fd))
@@ -171,7 +171,7 @@ pub fn posix_openpt(flags: fcntl::OFlag) -> Result<PtyMaster> {
 pub unsafe fn ptsname(fd: &PtyMaster) -> Result<String> {
     let name_ptr = libc::ptsname(fd.as_raw_fd());
     if name_ptr.is_null() {
-        return Err(Error::from(Errno::last()));
+        return Err(Errno::last());
     }
 
     let name = CStr::from_ptr(name_ptr);
@@ -195,7 +195,7 @@ pub fn ptsname_r(fd: &PtyMaster) -> Result<String> {
     let cname = unsafe {
         let cap = name_buf.capacity();
         if libc::ptsname_r(fd.as_raw_fd(), name_buf_ptr, cap) != 0 {
-            return Err(Error::last());
+            return Err(crate::Error::last());
         }
         CStr::from_ptr(name_buf.as_ptr())
     };
@@ -213,7 +213,7 @@ pub fn ptsname_r(fd: &PtyMaster) -> Result<String> {
 #[inline]
 pub fn unlockpt(fd: &PtyMaster) -> Result<()> {
     if unsafe { libc::unlockpt(fd.as_raw_fd()) } < 0 {
-        return Err(Error::from(Errno::last()));
+        return Err(Errno::last());
     }
 
     Ok(())
diff --git a/src/sched.rs b/src/sched.rs
index 69436fdf..c2dd7b84 100644
--- a/src/sched.rs
+++ b/src/sched.rs
@@ -15,7 +15,7 @@ mod sched_linux_like {
     use std::option::Option;
     use std::os::unix::io::RawFd;
     use crate::unistd::Pid;
-    use crate::{Error, Result};
+    use crate::Result;
 
     // For some functions taking with a parameter of type CloneFlags,
     // only a subset of these flags have an effect.
@@ -109,7 +109,7 @@ mod sched_linux_like {
         /// `field` is the CPU id to test
         pub fn is_set(&self, field: usize) -> Result<bool> {
             if field >= CpuSet::count() {
-                Err(Error::from(Errno::EINVAL))
+                Err(Errno::EINVAL)
             } else {
                 Ok(unsafe { libc::CPU_ISSET(field, &self.cpu_set) })
             }
@@ -119,7 +119,7 @@ mod sched_linux_like {
         /// `field` is the CPU id to add
         pub fn set(&mut self, field: usize) -> Result<()> {
             if field >= CpuSet::count() {
-                Err(Error::from(Errno::EINVAL))
+                Err(Errno::EINVAL)
             } else {
                 unsafe { libc::CPU_SET(field, &mut self.cpu_set); }
                 Ok(())
@@ -130,7 +130,7 @@ mod sched_linux_like {
         /// `field` is the CPU id to remove
         pub fn unset(&mut self, field: usize) -> Result<()> {
             if field >= CpuSet::count() {
-                Err(Error::from(Errno::EINVAL))
+                Err(Errno::EINVAL)
             } else {
                 unsafe { libc::CPU_CLR(field, &mut self.cpu_set);}
                 Ok(())
diff --git a/src/sys/aio.rs b/src/sys/aio.rs
index fcee28c5..e64a2a82 100644
--- a/src/sys/aio.rs
+++ b/src/sys/aio.rs
@@ -21,7 +21,7 @@
 //! [`aio_cancel_all`](fn.aio_cancel_all.html), though the operating system may
 //! not support this for all filesystems and devices.
 
-use crate::{Error, Result};
+use crate::Result;
 use crate::errno::Errno;
 use std::os::unix::io::RawFd;
 use libc::{c_void, off_t, size_t};
@@ -148,15 +148,13 @@ impl<'a> AioCb<'a> {
     /// # use std::{thread, time};
     /// # use std::os::unix::io::AsRawFd;
     /// # use tempfile::tempfile;
-    /// # fn main() {
     /// let f = tempfile().unwrap();
     /// let mut aiocb = AioCb::from_fd( f.as_raw_fd(), 0, SigevNone);
     /// aiocb.fsync(AioFsyncMode::O_SYNC).expect("aio_fsync failed early");
-    /// while (aiocb.error() == Err(Error::from(Errno::EINPROGRESS))) {
+    /// while (aiocb.error() == Err(Errno::EINPROGRESS)) {
     ///     thread::sleep(time::Duration::from_millis(10));
     /// }
     /// aiocb.aio_return().expect("aio_fsync failed late");
-    /// # }
     /// ```
     pub fn from_fd(fd: RawFd, prio: libc::c_int,
                     sigev_notify: SigevNotify) -> Pin<Box<AioCb<'a>>> {
@@ -229,7 +227,6 @@ impl<'a> AioCb<'a> {
     /// # use std::io::Write;
     /// # use std::os::unix::io::AsRawFd;
     /// # use tempfile::tempfile;
-    /// # fn main() {
     /// const INITIAL: &[u8] = b"abcdef123456";
     /// const LEN: usize = 4;
     /// let mut rbuf = vec![0; LEN];
@@ -243,13 +240,12 @@ impl<'a> AioCb<'a> {
     ///         SigevNotify::SigevNone,
     ///         LioOpcode::LIO_NOP);
     ///     aiocb.read().unwrap();
-    ///     while (aiocb.error() == Err(Error::from(Errno::EINPROGRESS))) {
+    ///     while (aiocb.error() == Err(Errno::EINPROGRESS)) {
     ///         thread::sleep(time::Duration::from_millis(10));
     ///     }
     ///     assert_eq!(aiocb.aio_return().unwrap() as usize, LEN);
     /// }
     /// assert_eq!(rbuf, b"cdef");
-    /// # }
     /// ```
     pub fn from_mut_slice(fd: RawFd, offs: off_t, buf: &'a mut [u8],
                           prio: libc::c_int, sigev_notify: SigevNotify,
@@ -404,7 +400,6 @@ impl<'a> AioCb<'a> {
     /// # use std::{thread, time};
     /// # use std::os::unix::io::AsRawFd;
     /// # use tempfile::tempfile;
-    /// # fn main() {
     /// const WBUF: &[u8] = b"abcdef123456";
     /// let mut f = tempfile().unwrap();
     /// let mut aiocb = AioCb::from_slice( f.as_raw_fd(),
@@ -414,11 +409,10 @@ impl<'a> AioCb<'a> {
     ///     SigevNotify::SigevNone,
     ///     LioOpcode::LIO_NOP);
     /// aiocb.write().unwrap();
-    /// while (aiocb.error() == Err(Error::from(Errno::EINPROGRESS))) {
+    /// while (aiocb.error() == Err(Errno::EINPROGRESS)) {
     ///     thread::sleep(time::Duration::from_millis(10));
     /// }
     /// assert_eq!(aiocb.aio_return().unwrap() as usize, WBUF.len());
-    /// # }
     /// ```
     // Note: another solution to the problem of writing const buffers would be
     // to genericize AioCb for both &mut [u8] and &[u8] buffers.  AioCb::read
@@ -480,7 +474,6 @@ impl<'a> AioCb<'a> {
     /// # use std::io::Write;
     /// # use std::os::unix::io::AsRawFd;
     /// # use tempfile::tempfile;
-    /// # fn main() {
     /// let wbuf = b"CDEF";
     /// let mut f = tempfile().unwrap();
     /// let mut aiocb = AioCb::from_slice( f.as_raw_fd(),
@@ -492,13 +485,12 @@ impl<'a> AioCb<'a> {
     /// aiocb.write().unwrap();
     /// let cs = aiocb.cancel().unwrap();
     /// if cs == AioCancelStat::AioNotCanceled {
-    ///     while (aiocb.error() == Err(Error::from(Errno::EINPROGRESS))) {
+    ///     while (aiocb.error() == Err(Errno::EINPROGRESS)) {
     ///         thread::sleep(time::Duration::from_millis(10));
     ///     }
     /// }
     /// // Must call `aio_return`, but ignore the result
     /// let _ = aiocb.aio_return();
-    /// # }
     /// ```
     ///
     /// # References
@@ -513,7 +505,7 @@ impl<'a> AioCb<'a> {
             libc::AIO_CANCELED => Ok(AioCancelStat::AioCanceled),
             libc::AIO_NOTCANCELED => Ok(AioCancelStat::AioNotCanceled),
             libc::AIO_ALLDONE => Ok(AioCancelStat::AioAllDone),
-            -1 => Err(Error::from(Errno::last())),
+            -1 => Err(Errno::last()),
             _ => panic!("unknown aio_cancel return value")
         }
     }
@@ -524,8 +516,8 @@ impl<'a> AioCb<'a> {
         };
         match r {
             0 => Ok(()),
-            num if num > 0 => Err(Error::from(Errno::from_i32(num))),
-            -1 => Err(Error::from(Errno::last())),
+            num if num > 0 => Err(Errno::from_i32(num)),
+            -1 => Err(Errno::last()),
             num => panic!("unknown aio_error return value {:?}", num)
         }
     }
@@ -548,7 +540,6 @@ impl<'a> AioCb<'a> {
     /// # use std::{thread, time};
     /// # use std::os::unix::io::AsRawFd;
     /// # use tempfile::tempfile;
-    /// # fn main() {
     /// const WBUF: &[u8] = b"abcdef123456";
     /// let mut f = tempfile().unwrap();
     /// let mut aiocb = AioCb::from_slice( f.as_raw_fd(),
@@ -558,11 +549,10 @@ impl<'a> AioCb<'a> {
     ///     SigevNotify::SigevNone,
     ///     LioOpcode::LIO_NOP);
     /// aiocb.write().unwrap();
-    /// while (aiocb.error() == Err(Error::from(Errno::EINPROGRESS))) {
+    /// while (aiocb.error() == Err(Errno::EINPROGRESS)) {
     ///     thread::sleep(time::Duration::from_millis(10));
     /// }
     /// assert_eq!(aiocb.aio_return().unwrap() as usize, WBUF.len());
-    /// # }
     /// ```
     ///
     /// # References
@@ -711,7 +701,6 @@ impl<'a> AioCb<'a> {
 /// # use std::io::Write;
 /// # use std::os::unix::io::AsRawFd;
 /// # use tempfile::tempfile;
-/// # fn main() {
 /// let wbuf = b"CDEF";
 /// let mut f = tempfile().unwrap();
 /// let mut aiocb = AioCb::from_slice( f.as_raw_fd(),
@@ -723,13 +712,12 @@ impl<'a> AioCb<'a> {
 /// aiocb.write().unwrap();
 /// let cs = aio_cancel_all(f.as_raw_fd()).unwrap();
 /// if cs == AioCancelStat::AioNotCanceled {
-///     while (aiocb.error() == Err(Error::from(Errno::EINPROGRESS))) {
+///     while (aiocb.error() == Err(Errno::EINPROGRESS)) {
 ///         thread::sleep(time::Duration::from_millis(10));
 ///     }
 /// }
 /// // Must call `aio_return`, but ignore the result
 /// let _ = aiocb.aio_return();
-/// # }
 /// ```
 ///
 /// # References
@@ -740,7 +728,7 @@ pub fn aio_cancel_all(fd: RawFd) -> Result<AioCancelStat> {
         libc::AIO_CANCELED => Ok(AioCancelStat::AioCanceled),
         libc::AIO_NOTCANCELED => Ok(AioCancelStat::AioNotCanceled),
         libc::AIO_ALLDONE => Ok(AioCancelStat::AioAllDone),
-        -1 => Err(Error::from(Errno::last())),
+        -1 => Err(Errno::last()),
         _ => panic!("unknown aio_cancel return value")
     }
 }
@@ -759,7 +747,6 @@ pub fn aio_cancel_all(fd: RawFd) -> Result<AioCancelStat> {
 /// # use nix::sys::signal::SigevNotify;
 /// # use std::os::unix::io::AsRawFd;
 /// # use tempfile::tempfile;
-/// # fn main() {
 /// const WBUF: &[u8] = b"abcdef123456";
 /// let mut f = tempfile().unwrap();
 /// let mut aiocb = AioCb::from_slice( f.as_raw_fd(),
@@ -771,7 +758,6 @@ pub fn aio_cancel_all(fd: RawFd) -> Result<AioCancelStat> {
 /// aiocb.write().unwrap();
 /// aio_suspend(&[aiocb.as_ref()], None).expect("aio_suspend failed");
 /// assert_eq!(aiocb.aio_return().unwrap() as usize, WBUF.len());
-/// # }
 /// ```
 /// # References
 ///
@@ -876,7 +862,6 @@ impl<'a> LioCb<'a> {
     /// # use nix::sys::signal::SigevNotify;
     /// # use std::os::unix::io::AsRawFd;
     /// # use tempfile::tempfile;
-    /// # fn main() {
     /// const WBUF: &[u8] = b"abcdef123456";
     /// let mut f = tempfile().unwrap();
     /// let mut liocb = LioCbBuilder::with_capacity(1)
@@ -891,7 +876,6 @@ impl<'a> LioCb<'a> {
     /// liocb.listio(LioMode::LIO_WAIT,
     ///              SigevNotify::SigevNone).unwrap();
     /// assert_eq!(liocb.aio_return(0).unwrap() as usize, WBUF.len());
-    /// # }
     /// ```
     ///
     /// # References
@@ -936,7 +920,6 @@ impl<'a> LioCb<'a> {
     /// # use std::os::unix::io::AsRawFd;
     /// # use std::{thread, time};
     /// # use tempfile::tempfile;
-    /// # fn main() {
     /// const WBUF: &[u8] = b"abcdef123456";
     /// let mut f = tempfile().unwrap();
     /// let mut liocb = LioCbBuilder::with_capacity(1)
@@ -949,13 +932,12 @@ impl<'a> LioCb<'a> {
     ///         LioOpcode::LIO_WRITE
     ///     ).finish();
     /// let mut err = liocb.listio(LioMode::LIO_WAIT, SigevNotify::SigevNone);
-    /// while err == Err(Error::from(Errno::EIO)) ||
-    ///       err == Err(Error::from(Errno::EAGAIN)) {
+    /// while err == Err(Errno::EIO) ||
+    ///       err == Err(Errno::EAGAIN) {
     ///     thread::sleep(time::Duration::from_millis(10));
     ///     err = liocb.listio_resubmit(LioMode::LIO_WAIT, SigevNotify::SigevNone);
     /// }
     /// assert_eq!(liocb.aio_return(0).unwrap() as usize, WBUF.len());
-    /// # }
     /// ```
     ///
     /// # References
diff --git a/src/sys/epoll.rs b/src/sys/epoll.rs
index 9f68d5ce..6bc2a253 100644
--- a/src/sys/epoll.rs
+++ b/src/sys/epoll.rs
@@ -1,4 +1,4 @@
-use crate::{Error, Result};
+use crate::Result;
 use crate::errno::Errno;
 use libc::{self, c_int};
 use std::os::unix::io::RawFd;
@@ -86,7 +86,7 @@ pub fn epoll_ctl<'a, T>(epfd: RawFd, op: EpollOp, fd: RawFd, event: T) -> Result
 {
     let mut event: Option<&mut EpollEvent> = event.into();
     if event.is_none() && op != EpollOp::EpollCtlDel {
-        Err(Error::from(Errno::EINVAL))
+        Err(Errno::EINVAL)
     } else {
         let res = unsafe {
             if let Some(ref mut event) = event {
diff --git a/src/sys/eventfd.rs b/src/sys/eventfd.rs
index baaaa89d..c54f952f 100644
--- a/src/sys/eventfd.rs
+++ b/src/sys/eventfd.rs
@@ -1,4 +1,3 @@
-use libc;
 use std::os::unix::io::RawFd;
 use crate::Result;
 use crate::errno::Errno;
diff --git a/src/sys/memfd.rs b/src/sys/memfd.rs
index 51b7e6b1..0236eef6 100644
--- a/src/sys/memfd.rs
+++ b/src/sys/memfd.rs
@@ -1,4 +1,3 @@
-use libc;
 use std::os::unix::io::RawFd;
 use crate::Result;
 use crate::errno::Errno;
diff --git a/src/sys/mman.rs b/src/sys/mman.rs
index e3c36208..0ea7edaf 100644
--- a/src/sys/mman.rs
+++ b/src/sys/mman.rs
@@ -1,4 +1,4 @@
-use crate::{Error, Result};
+use crate::Result;
 #[cfg(not(target_os = "android"))]
 use crate::NixPath;
 use crate::errno::Errno;
@@ -333,7 +333,7 @@ pub unsafe fn mmap(addr: *mut c_void, length: size_t, prot: ProtFlags, flags: Ma
     let ret = libc::mmap(addr, length, prot.bits(), flags.bits(), fd, offset);
 
     if ret == libc::MAP_FAILED {
-        Err(Error::from(Errno::last()))
+        Err(Errno::last())
     } else {
         Ok(ret)
     }
@@ -366,7 +366,7 @@ pub unsafe fn mremap(
         );
 
     if ret == libc::MAP_FAILED {
-        Err(Error::from(Errno::last()))
+        Err(Errno::last())
     } else {
         Ok(ret)
     }
diff --git a/src/sys/personality.rs b/src/sys/personality.rs
index 6548b654..b15956c4 100644
--- a/src/sys/personality.rs
+++ b/src/sys/personality.rs
@@ -39,7 +39,7 @@ pub fn get() -> Result<Persona> {
         libc::personality(0xFFFFFFFF)
     };
 
-    Errno::result(res).map(|r| Persona::from_bits_truncate(r))
+    Errno::result(res).map(Persona::from_bits_truncate)
 }
 
 /// Set the current process personality.
@@ -66,5 +66,5 @@ pub fn set(persona: Persona) -> Result<Persona> {
         libc::personality(persona.bits() as c_ulong)
     };
 
-    Errno::result(res).map(|r| Persona::from_bits_truncate(r))
+    Errno::result(res).map(Persona::from_bits_truncate)
 }
diff --git a/src/sys/ptrace/linux.rs b/src/sys/ptrace/linux.rs
index 1bfde0d2..37236790 100644
--- a/src/sys/ptrace/linux.rs
+++ b/src/sys/ptrace/linux.rs
@@ -415,16 +415,15 @@ 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);
 ///     }
+///     _ => {},
 /// }
 /// ```
 pub fn step<T: Into<Option<Signal>>>(pid: Pid, sig: T) -> Result<()> {
diff --git a/src/sys/reboot.rs b/src/sys/reboot.rs
index be5067a9..46ab68b6 100644
--- a/src/sys/reboot.rs
+++ b/src/sys/reboot.rs
@@ -1,8 +1,7 @@
 //! Reboot/shutdown or enable/disable Ctrl-Alt-Delete.
 
-use crate::{Error, Result};
+use crate::Result;
 use crate::errno::Errno;
-use libc;
 use std::convert::Infallible;
 use std::mem::drop;
 
@@ -27,7 +26,7 @@ pub fn reboot(how: RebootMode) -> Result<Infallible> {
     unsafe {
         libc::reboot(how as libc::c_int)
     };
-    Err(Error::from(Errno::last()))
+    Err(Errno::last())
 }
 
 /// Enable or disable the reboot keystroke (Ctrl-Alt-Delete).
diff --git a/src/sys/select.rs b/src/sys/select.rs
index 0a0e830d..5f3337f3 100644
--- a/src/sys/select.rs
+++ b/src/sys/select.rs
@@ -111,7 +111,7 @@ impl<'a> Iterator for Fds<'a> {
     type Item = RawFd;
 
     fn next(&mut self) -> Option<RawFd> {
-        while let Some(i) = self.range.next() {
+        for i in &mut self.range {
             if self.set.contains(i as RawFd) {
                 return Some(i as RawFd);
             }
diff --git a/src/sys/signal.rs b/src/sys/signal.rs
index 1011930f..e8c79d33 100644
--- a/src/sys/signal.rs
+++ b/src/sys/signal.rs
@@ -156,7 +156,7 @@ impl FromStr for Signal {
                           target_os = "fuchsia", target_os = "linux",
                           target_os = "redox")))]
             "SIGINFO" => Signal::SIGINFO,
-            _ => return Err(Error::from(Errno::EINVAL)),
+            _ => return Err(Errno::EINVAL),
         })
     }
 }
@@ -779,7 +779,7 @@ pub unsafe fn signal(signal: Signal, handler: SigHandler) -> Result<SigHandler>
         SigHandler::SigIgn => libc::signal(signal, libc::SIG_IGN),
         SigHandler::Handler(handler) => libc::signal(signal, handler as libc::sighandler_t),
         #[cfg(not(target_os = "redox"))]
-        SigHandler::SigAction(_) => return Err(Error::from(Errno::ENOTSUP)),
+        SigHandler::SigAction(_) => return Err(Errno::ENOTSUP),
     };
     Errno::result(res).map(|oldhandler| {
         match oldhandler {
@@ -1091,7 +1091,7 @@ mod tests {
 
     #[test]
     fn test_from_str_invalid_value() {
-        let errval = Err(Error::from(Errno::EINVAL));
+        let errval = Err(Errno::EINVAL);
         assert_eq!("NOSIGNAL".parse::<Signal>(), errval);
         assert_eq!("kill".parse::<Signal>(), errval);
         assert_eq!("9".parse::<Signal>(), errval);
diff --git a/src/sys/signalfd.rs b/src/sys/signalfd.rs
index 2ede8b8f..bc4a4522 100644
--- a/src/sys/signalfd.rs
+++ b/src/sys/signalfd.rs
@@ -15,9 +15,8 @@
 //!
 //! Please note that signal discarding is not specific to `signalfd`, but also happens with regular
 //! signal handlers.
-use libc;
 use crate::unistd;
-use crate::{Error, Result};
+use crate::Result;
 use crate::errno::Errno;
 pub use crate::sys::signal::{self, SigSet};
 pub use libc::signalfd_siginfo as siginfo;
@@ -117,7 +116,7 @@ impl SignalFd {
 impl Drop for SignalFd {
     fn drop(&mut self) {
         let e = unistd::close(self.0);
-        if !std::thread::panicking() && e == Err(Error::from(Errno::EBADF)) {
+        if !std::thread::panicking() && e == Err(Errno::EBADF) {
             panic!("Closing an invalid file descriptor!");
         };
     }
diff --git a/src/sys/socket/addr.rs b/src/sys/socket/addr.rs
index 38dd4190..832a153f 100644
--- a/src/sys/socket/addr.rs
+++ b/src/sys/socket/addr.rs
@@ -1,5 +1,5 @@
 use super::sa_family_t;
-use crate::{Error, Result, NixPath};
+use crate::{Result, NixPath};
 use crate::errno::Errno;
 use memoffset::offset_of;
 use std::{fmt, mem, net, ptr, slice};
@@ -270,6 +270,7 @@ pub enum InetAddr {
 }
 
 impl InetAddr {
+    #[allow(clippy::needless_update)]   // It isn't needless on all OSes
     pub fn from_std(std: &net::SocketAddr) -> InetAddr {
         match *std {
             net::SocketAddr::V4(ref addr) => {
@@ -293,6 +294,7 @@ impl InetAddr {
         }
     }
 
+    #[allow(clippy::needless_update)]   // It isn't needless on all OSes
     pub fn new(ip: IpAddr, port: u16) -> InetAddr {
         match ip {
             IpAddr::V4(ref ip) => {
@@ -565,7 +567,7 @@ impl UnixAddr {
                 let bytes = cstr.to_bytes();
 
                 if bytes.len() >= ret.sun_path.len() {
-                    return Err(Error::from(Errno::ENAMETOOLONG));
+                    return Err(Errno::ENAMETOOLONG);
                 }
 
                 ptr::copy_nonoverlapping(bytes.as_ptr(),
@@ -592,7 +594,7 @@ impl UnixAddr {
             };
 
             if path.len() >= ret.sun_path.len() {
-                return Err(Error::from(Errno::ENAMETOOLONG));
+                return Err(Errno::ENAMETOOLONG);
             }
 
             // Abstract addresses are represented by sun_path[0] ==
@@ -751,7 +753,7 @@ impl SockAddr {
 
     #[cfg(any(target_os = "ios", target_os = "macos"))]
     pub fn new_sys_control(sockfd: RawFd, name: &str, unit: u32) -> Result<SockAddr> {
-        SysControlAddr::from_name(sockfd, name, unit).map(|a| SockAddr::SysControl(a))
+        SysControlAddr::from_name(sockfd, name, unit).map(SockAddr::SysControl)
     }
 
     #[cfg(any(target_os = "android", target_os = "linux"))]
@@ -1064,7 +1066,7 @@ pub mod sys_control {
     use libc::{self, c_uchar};
     use std::{fmt, mem};
     use std::os::unix::io::RawFd;
-    use crate::{Errno, Error, Result};
+    use crate::{Errno, Result};
 
     // FIXME: Move type into `libc`
     #[repr(C)]
@@ -1075,7 +1077,7 @@ pub mod sys_control {
         pub ctl_name: [c_uchar; MAX_KCTL_NAME],
     }
 
-    const CTL_IOC_MAGIC: u8 = 'N' as u8;
+    const CTL_IOC_MAGIC: u8 = b'N';
     const CTL_IOC_INFO: u8 = 3;
     const MAX_KCTL_NAME: usize = 96;
 
@@ -1101,7 +1103,7 @@ pub mod sys_control {
 
         pub fn from_name(sockfd: RawFd, name: &str, unit: u32) -> Result<SysControlAddr> {
             if name.len() > MAX_KCTL_NAME {
-                return Err(Error::from(Errno::ENAMETOOLONG));
+                return Err(Errno::ENAMETOOLONG);
             }
 
             let mut ctl_name = [0; MAX_KCTL_NAME];
diff --git a/src/sys/socket/mod.rs b/src/sys/socket/mod.rs
index 96328842..97eea3dc 100644
--- a/src/sys/socket/mod.rs
+++ b/src/sys/socket/mod.rs
@@ -2,7 +2,7 @@
 //!
 //! [Further reading](https://man7.org/linux/man-pages/man7/socket.7.html)
 use cfg_if::cfg_if;
-use crate::{Error, Result, errno::Errno};
+use crate::{Result, errno::Errno};
 use libc::{self, c_void, c_int, iovec, socklen_t, size_t,
         CMSG_FIRSTHDR, CMSG_NXTHDR, CMSG_DATA, CMSG_LEN};
 use memoffset::offset_of;
@@ -311,9 +311,9 @@ cfg_if! {
             }
         }
 
-        impl Into<libc::ucred> for UnixCredentials {
-            fn into(self) -> libc::ucred {
-                self.0
+        impl From<UnixCredentials> for libc::ucred {
+            fn from(uc: UnixCredentials) -> Self {
+                uc.0
             }
         }
     } else if #[cfg(any(target_os = "freebsd", target_os = "dragonfly"))] {
@@ -1300,6 +1300,7 @@ pub struct RecvMmsgData<'a, I>
     target_os = "freebsd",
     target_os = "netbsd",
 ))]
+#[allow(clippy::needless_collect)]  // Complicated false positive
 pub fn recvmmsg<'a, I>(
     fd: RawFd,
     data: impl std::iter::IntoIterator<Item=&'a mut RecvMmsgData<'a, I>,
@@ -1813,7 +1814,7 @@ pub fn sockaddr_storage_to_addr(
 
     assert!(len <= mem::size_of::<sockaddr_storage>());
     if len < mem::size_of_val(&addr.ss_family) {
-        return Err(Error::from(Errno::ENOTCONN));
+        return Err(Errno::ENOTCONN);
     }
 
     match c_int::from(addr.ss_family) {
diff --git a/src/sys/statvfs.rs b/src/sys/statvfs.rs
index 508fa8db..15e7a7d4 100644
--- a/src/sys/statvfs.rs
+++ b/src/sys/statvfs.rs
@@ -150,7 +150,7 @@ mod test {
 
     #[test]
     fn statvfs_call() {
-        statvfs("/".as_bytes()).unwrap();
+        statvfs(&b"/"[..]).unwrap();
     }
 
     #[test]
diff --git a/src/sys/timerfd.rs b/src/sys/timerfd.rs
index 5d87b7c2..705a3c4d 100644
--- a/src/sys/timerfd.rs
+++ b/src/sys/timerfd.rs
@@ -257,14 +257,9 @@ impl TimerFd {
     ///
     /// Note: If the alarm is unset, then you will wait forever.
     pub fn wait(&self) -> Result<()> {
-        loop {
-            if let Err(e) = read(self.fd, &mut [0u8; 8]) {
-                match e {
-                    Errno::EINTR => continue,
-                    _ => return Err(e),
-                }
-            } else {
-                break;
+        while let Err(e) = read(self.fd, &mut [0u8; 8]) {
+            if e != Errno::EINTR {
+                return Err(e)
             }
         }
 
diff --git a/src/time.rs b/src/time.rs
index 1731e60e..6275b59c 100644
--- a/src/time.rs
+++ b/src/time.rs
@@ -6,7 +6,7 @@ use crate::sys::time::TimeSpec;
     target_os = "android",
     target_os = "emscripten",
 ))]
-use crate::{unistd::Pid, Error};
+use crate::unistd::Pid;
 use crate::{Errno, Result};
 use libc::{self, clockid_t};
 use std::mem::MaybeUninit;
@@ -255,6 +255,6 @@ pub fn clock_getcpuclockid(pid: Pid) -> Result<ClockId> {
         let res = unsafe { clk_id.assume_init() };
         Ok(ClockId::from(res))
     } else {
-        Err(Error::from(Errno::from_i32(ret)))
+        Err(Errno::from_i32(ret))
     }
 }
diff --git a/src/ucontext.rs b/src/ucontext.rs
index a5b8cc75..f2338bd4 100644
--- a/src/ucontext.rs
+++ b/src/ucontext.rs
@@ -1,4 +1,3 @@
-use libc;
 #[cfg(not(target_env = "musl"))]
 use crate::Result;
 #[cfg(not(target_env = "musl"))]
diff --git a/src/unistd.rs b/src/unistd.rs
index 2f47b260..64759dc6 100644
--- a/src/unistd.rs
+++ b/src/unistd.rs
@@ -180,10 +180,7 @@ impl ForkResult {
     /// Return `true` if this is the child process of the `fork()`
     #[inline]
     pub fn is_child(self) -> bool {
-        match self {
-            ForkResult::Child => true,
-            _ => false
-        }
+        matches!(self, ForkResult::Child)
     }
 
     /// Returns `true` if this is the parent process of the `fork()`
@@ -398,7 +395,7 @@ pub fn dup3(oldfd: RawFd, newfd: RawFd, flags: OFlag) -> Result<RawFd> {
 #[inline]
 fn dup3_polyfill(oldfd: RawFd, newfd: RawFd, flags: OFlag) -> Result<RawFd> {
     if oldfd == newfd {
-        return Err(Error::from(Errno::EINVAL));
+        return Err(Errno::EINVAL);
     }
 
     let fd = dup2(oldfd, newfd)?;
@@ -572,7 +569,7 @@ fn reserve_double_buffer_size<T>(buf: &mut Vec<T>, limit: usize) -> Result<()> {
     use std::cmp::min;
 
     if buf.capacity() >= limit {
-        return Err(Error::from(Errno::ERANGE))
+        return Err(Errno::ERANGE)
     }
 
     let capacity = min(buf.capacity() * 2, limit);
@@ -615,9 +612,9 @@ pub fn getcwd() -> Result<PathBuf> {
                 let error = Errno::last();
                 // ERANGE means buffer was too small to store directory name
                 if error != Errno::ERANGE {
-                    return Err(Error::from(error));
+                    return Err(error);
                 }
-            }
+           }
 
             // Trigger the internal buffer resizing logic.
             reserve_double_buffer_size(&mut buf, PATH_MAX as usize)?;
@@ -739,7 +736,7 @@ pub fn execv<S: AsRef<CStr>>(path: &CStr, argv: &[S]) -> Result<Infallible> {
         libc::execv(path.as_ptr(), args_p.as_ptr())
     };
 
-    Err(Error::from(Errno::last()))
+    Err(Errno::last())
 }
 
 
@@ -764,7 +761,7 @@ pub fn execve<SA: AsRef<CStr>, SE: AsRef<CStr>>(path: &CStr, args: &[SA], env: &
         libc::execve(path.as_ptr(), args_p.as_ptr(), env_p.as_ptr())
     };
 
-    Err(Error::from(Errno::last()))
+    Err(Errno::last())
 }
 
 /// Replace the current process image with a new one and replicate shell `PATH`
@@ -784,7 +781,7 @@ pub fn execvp<S: AsRef<CStr>>(filename: &CStr, args: &[S]) -> Result<Infallible>
         libc::execvp(filename.as_ptr(), args_p.as_ptr())
     };
 
-    Err(Error::from(Errno::last()))
+    Err(Errno::last())
 }
 
 /// Replace the current process image with a new one and replicate shell `PATH`
@@ -805,7 +802,7 @@ pub fn execvpe<SA: AsRef<CStr>, SE: AsRef<CStr>>(filename: &CStr, args: &[SA], e
         libc::execvpe(filename.as_ptr(), args_p.as_ptr(), env_p.as_ptr())
     };
 
-    Err(Error::from(Errno::last()))
+    Err(Errno::last())
 }
 
 /// Replace the current process image with a new one (see
@@ -833,7 +830,7 @@ pub fn fexecve<SA: AsRef<CStr> ,SE: AsRef<CStr>>(fd: RawFd, args: &[SA], env: &[
         libc::fexecve(fd, args_p.as_ptr(), env_p.as_ptr())
     };
 
-    Err(Error::from(Errno::last()))
+    Err(Errno::last())
 }
 
 /// Execute program relative to a directory file descriptor (see
@@ -858,7 +855,7 @@ pub fn execveat<SA: AsRef<CStr>,SE: AsRef<CStr>>(dirfd: RawFd, pathname: &CStr,
                       args_p.as_ptr(), env_p.as_ptr(), flags);
     };
 
-    Err(Error::from(Errno::last()))
+    Err(Errno::last())
 }
 
 /// Daemonize this process by detaching from the controlling terminal (see
@@ -1138,9 +1135,9 @@ pub fn isatty(fd: RawFd) -> Result<bool> {
         } else {
             match Errno::last() {
                 Errno::ENOTTY => Ok(false),
-                err => Err(Error::from(err)),
+                err => Err(err),
             }
-        }
+       }
     }
 }
 
@@ -1449,7 +1446,7 @@ pub fn getgroups() -> Result<Vec<Gid>> {
                 // EINVAL indicates that the buffer size was too
                 // small, resize it up to ngroups_max as limit.
                 reserve_double_buffer_size(&mut groups, ngroups_max)
-                    .or(Err(Error::from(Errno::EINVAL)))?;
+                    .or(Err(Errno::EINVAL))?;
             },
             Err(e) => return Err(e)
         }
@@ -1571,7 +1568,7 @@ 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)
-                .map_err(|_| Error::from(Errno::EINVAL))?;
+                .map_err(|_| Errno::EINVAL)?;
         }
     }
 }
@@ -1930,7 +1927,7 @@ pub fn fpathconf(fd: RawFd, var: PathconfVar) -> Result<Option<c_long>> {
         if errno::errno() == 0 {
             Ok(None)
         } else {
-            Err(Error::from(Errno::last()))
+            Err(Errno::last())
         }
     } else {
         Ok(Some(raw))
@@ -1969,7 +1966,7 @@ pub fn pathconf<P: ?Sized + NixPath>(path: &P, var: PathconfVar) -> Result<Optio
         if errno::errno() == 0 {
             Ok(None)
         } else {
-            Err(Error::from(Errno::last()))
+            Err(Errno::last())
         }
     } else {
         Ok(Some(raw))
@@ -2469,7 +2466,7 @@ pub fn sysconf(var: SysconfVar) -> Result<Option<c_long>> {
         if errno::errno() == 0 {
             Ok(None)
         } else {
-            Err(Error::from(Errno::last()))
+            Err(Errno::last())
         }
     } else {
         Ok(Some(raw))
@@ -2788,7 +2785,7 @@ impl User {
                 // Trigger the internal buffer resizing logic.
                 reserve_double_buffer_size(&mut cbuf, buflimit)?;
             } else {
-                return Err(Error::from(Errno::last()));
+                return Err(Errno::last());
             }
         }
     }
@@ -2909,7 +2906,7 @@ impl Group {
                 // Trigger the internal buffer resizing logic.
                 reserve_double_buffer_size(&mut cbuf, buflimit)?;
             } else {
-                return Err(Error::from(Errno::last()));
+                return Err(Errno::last());
             }
         }
     }
@@ -2968,7 +2965,7 @@ pub fn ttyname(fd: RawFd) -> Result<PathBuf> {
 
     let ret = unsafe { libc::ttyname_r(fd, c_buf, buf.len()) };
     if ret != 0 {
-        return Err(Error::from(Errno::from_i32(ret)));
+        return Err(Errno::from_i32(ret));
     }
 
     let nul = buf.iter().position(|c| *c == b'\0').unwrap();
diff --git a/test/sys/test_aio.rs b/test/sys/test_aio.rs
index 3208410e..b4eb3129 100644
--- a/test/sys/test_aio.rs
+++ b/test/sys/test_aio.rs
@@ -1,5 +1,5 @@
 use libc::{c_int, c_void};
-use nix::{Error, Result};
+use nix::Result;
 use nix::errno::*;
 use nix::sys::aio::*;
 use nix::sys::signal::{SaFlags, SigAction, sigaction, SigevNotify, SigHandler, Signal, SigSet};
@@ -16,7 +16,7 @@ use tempfile::tempfile;
 fn poll_aio(aiocb: &mut Pin<Box<AioCb>>) -> Result<()> {
     loop {
         let err = aiocb.error();
-        if err != Err(Error::from(Errno::EINPROGRESS)) { return err; };
+        if err != Err(Errno::EINPROGRESS) { return err; };
         thread::sleep(time::Duration::from_millis(10));
     }
 }
@@ -26,7 +26,7 @@ fn poll_aio(aiocb: &mut Pin<Box<AioCb>>) -> Result<()> {
 fn poll_lio(liocb: &mut LioCb, i: usize) -> Result<()> {
     loop {
         let err = liocb.error(i);
-        if err != Err(Error::from(Errno::EINPROGRESS)) { return err; };
+        if err != Err(Errno::EINPROGRESS) { return err; };
         thread::sleep(time::Duration::from_millis(10));
     }
 }
@@ -70,7 +70,7 @@ fn test_cancel() {
                             LioOpcode::LIO_NOP);
     aiocb.write().unwrap();
     let err = aiocb.error();
-    assert!(err == Ok(()) || err == Err(Error::from(Errno::EINPROGRESS)));
+    assert!(err == Ok(()) || err == Err(Errno::EINPROGRESS));
 
     let cancelstat = aiocb.cancel();
     assert!(cancelstat.is_ok());
@@ -95,7 +95,7 @@ fn test_aio_cancel_all() {
                             LioOpcode::LIO_NOP);
     aiocb.write().unwrap();
     let err = aiocb.error();
-    assert!(err == Ok(()) || err == Err(Error::from(Errno::EINPROGRESS)));
+    assert!(err == Ok(()) || err == Err(Errno::EINPROGRESS));
 
     let cancelstat = aio_cancel_all(f.as_raw_fd());
     assert!(cancelstat.is_ok());
@@ -182,8 +182,8 @@ fn test_aio_suspend() {
                 Ok(_) => ()
             };
         }
-        if rcb.error() != Err(Error::from(Errno::EINPROGRESS)) &&
-           wcb.error() != Err(Error::from(Errno::EINPROGRESS)) {
+        if rcb.error() != Err(Errno::EINPROGRESS) &&
+           wcb.error() != Err(Errno::EINPROGRESS) {
             break
         }
     }
diff --git a/test/sys/test_epoll.rs b/test/sys/test_epoll.rs
index 57bc4844..8d44cd08 100644
--- a/test/sys/test_epoll.rs
+++ b/test/sys/test_epoll.rs
@@ -1,6 +1,5 @@
 use nix::sys::epoll::{EpollCreateFlags, EpollFlags, EpollOp, EpollEvent};
 use nix::sys::epoll::{epoll_create1, epoll_ctl};
-use nix::Error;
 use nix::errno::Errno;
 
 #[test]
@@ -8,11 +7,11 @@ pub fn test_epoll_errno() {
     let efd = epoll_create1(EpollCreateFlags::empty()).unwrap();
     let result = epoll_ctl(efd, EpollOp::EpollCtlDel, 1, None);
     assert!(result.is_err());
-    assert_eq!(result.unwrap_err(), Error::from(Errno::ENOENT));
+    assert_eq!(result.unwrap_err(), Errno::ENOENT);
 
     let result = epoll_ctl(efd, EpollOp::EpollCtlAdd, 1, None);
     assert!(result.is_err());
-    assert_eq!(result.unwrap_err(), Error::from(Errno::EINVAL));
+    assert_eq!(result.unwrap_err(), Errno::EINVAL);
 }
 
 #[test]
diff --git a/test/sys/test_inotify.rs b/test/sys/test_inotify.rs
index 121b726c..137816a3 100644
--- a/test/sys/test_inotify.rs
+++ b/test/sys/test_inotify.rs
@@ -1,7 +1,5 @@
 use nix::sys::inotify::{AddWatchFlags,InitFlags,Inotify};
-use nix::Error;
 use nix::errno::Errno;
-use tempfile;
 use std::ffi::OsString;
 use std::fs::{rename, File};
 
@@ -14,7 +12,7 @@ pub fn test_inotify() {
     instance.add_watch(tempdir.path(), AddWatchFlags::IN_ALL_EVENTS).unwrap();
 
     let events = instance.read_events();
-    assert_eq!(events.unwrap_err(), Error::from(Errno::EAGAIN));
+    assert_eq!(events.unwrap_err(), Errno::EAGAIN);
 
     File::create(tempdir.path().join("test")).unwrap();
 
@@ -31,7 +29,7 @@ pub fn test_inotify_multi_events() {
     instance.add_watch(tempdir.path(), AddWatchFlags::IN_ALL_EVENTS).unwrap();
 
     let events = instance.read_events();
-    assert_eq!(events.unwrap_err(), Error::from(Errno::EAGAIN));
+    assert_eq!(events.unwrap_err(), Errno::EAGAIN);
 
     File::create(tempdir.path().join("test")).unwrap();
     rename(tempdir.path().join("test"), tempdir.path().join("test2")).unwrap();
diff --git a/test/sys/test_socket.rs b/test/sys/test_socket.rs
index 6b998cb6..0f6fac66 100644
--- a/test/sys/test_socket.rs
+++ b/test/sys/test_socket.rs
@@ -152,7 +152,7 @@ pub fn test_abstract_sun_path_too_long() {
 pub fn test_addr_equality_abstract() {
     let name = String::from("nix\0abstract\0test");
     let addr1 = UnixAddr::new_abstract(name.as_bytes()).unwrap();
-    let mut addr2 = addr1.clone();
+    let mut addr2 = addr1;
 
     assert_eq!(addr1, addr2);
     assert_eq!(calculate_hash(&addr1), calculate_hash(&addr2));
@@ -367,7 +367,6 @@ mod recvfrom {
         target_os = "freebsd",
         target_os = "netbsd",
     ))]
-    #[allow(clippy::vec_init_then_push)]
     #[test]
     pub fn udp_sendmmsg() {
         use nix::sys::uio::IoVec;
@@ -394,14 +393,14 @@ mod recvfrom {
 
         let from = sendrecv(rsock, ssock, move |s, m, flags| {
             let iov = [IoVec::from_slice(m)];
-            let mut msgs = Vec::new();
-            msgs.push(
+            let mut msgs = vec![
                 SendMmsgData {
                     iov: &iov,
                     cmsgs: &[],
                     addr: Some(sock_addr),
                     _lt: Default::default(),
-                });
+                }
+            ];
 
             let batch_size = 15;
 
@@ -640,7 +639,6 @@ pub fn test_scm_rights() {
 #[cfg_attr(qemu, ignore)]
 #[test]
 pub fn test_af_alg_cipher() {
-    use libc;
     use nix::sys::uio::IoVec;
     use nix::unistd::read;
     use nix::sys::socket::{socket, sendmsg, bind, accept, setsockopt,
@@ -837,7 +835,7 @@ pub fn test_sendmsg_ipv4packetinfo() {
     if let InetAddr::V4(sin) = inet_addr {
         cfg_if! {
             if #[cfg(target_os = "netbsd")] {
-                drop(sin);
+                let _dontcare = sin;
                 let pi = libc::in_pktinfo {
                     ipi_ifindex: 0, /* Unspecified interface */
                     ipi_addr: libc::in_addr { s_addr: 0 },
@@ -925,7 +923,6 @@ fn test_scm_rights_single_cmsg_multiple_fds() {
     use nix::sys::socket::{ControlMessage, ControlMessageOwned, MsgFlags,
         sendmsg, recvmsg};
     use nix::sys::uio::IoVec;
-    use libc;
 
     let (send, receive) = UnixDatagram::pair().unwrap();
     let thread = thread::spawn(move || {
@@ -1068,8 +1065,6 @@ fn test_scm_credentials() {
 #[cfg_attr(qemu, ignore)]
 #[test]
 fn test_scm_credentials_and_rights() {
-    use libc;
-
     let space = cmsg_space!(libc::ucred, RawFd);
     test_impl_scm_credentials_and_rights(space);
 }
@@ -1278,7 +1273,6 @@ fn loopback_address(family: AddressFamily) -> Option<nix::ifaddrs::InterfaceAddr
 ), ignore)]
 #[test]
 pub fn test_recv_ipv4pktinfo() {
-    use libc;
     use nix::sys::socket::sockopt::Ipv4PacketInfo;
     use nix::sys::socket::{bind, SockFlag, SockType};
     use nix::sys::socket::{getsockname, setsockopt, socket};
@@ -1331,18 +1325,15 @@ pub fn test_recv_ipv4pktinfo() {
         );
 
         let mut cmsgs = msg.cmsgs();
-        match cmsgs.next() {
-            Some(ControlMessageOwned::Ipv4PacketInfo(pktinfo)) => {
-                let i = if_nametoindex(lo_name.as_bytes()).expect("if_nametoindex");
-                assert_eq!(
-                    pktinfo.ipi_ifindex as libc::c_uint,
-                    i,
-                    "unexpected ifindex (expected {}, got {})",
-                    i,
-                    pktinfo.ipi_ifindex
-                );
-            }
-            _ => (),
+        if let Some(ControlMessageOwned::Ipv4PacketInfo(pktinfo)) = cmsgs.next() {
+            let i = if_nametoindex(lo_name.as_bytes()).expect("if_nametoindex");
+            assert_eq!(
+                pktinfo.ipi_ifindex as libc::c_uint,
+                i,
+                "unexpected ifindex (expected {}, got {})",
+                i,
+                pktinfo.ipi_ifindex
+            );
         }
         assert!(cmsgs.next().is_none(), "unexpected additional control msg");
         assert_eq!(msg.bytes, 8);
@@ -1371,7 +1362,6 @@ pub fn test_recv_ipv4pktinfo() {
 ), ignore)]
 #[test]
 pub fn test_recvif() {
-    use libc;
     use nix::net::if_::*;
     use nix::sys::socket::sockopt::{Ipv4RecvIf, Ipv4RecvDstAddr};
     use nix::sys::socket::{bind, SockFlag, SockType};
@@ -1485,7 +1475,6 @@ pub fn test_recvif() {
 ), ignore)]
 #[test]
 pub fn test_recv_ipv6pktinfo() {
-    use libc;
     use nix::net::if_::*;
     use nix::sys::socket::sockopt::Ipv6RecvPacketInfo;
     use nix::sys::socket::{bind, SockFlag, SockType};
@@ -1562,7 +1551,6 @@ pub fn test_recv_ipv6pktinfo() {
 #[cfg_attr(graviton, ignore = "Not supported by the CI environment")]
 #[test]
 pub fn test_vsock() {
-    use libc;
     use nix::errno::Errno;
     use nix::sys::socket::{AddressFamily, socket, bind, connect, listen,
                            SockAddr, SockType, SockFlag};
@@ -1838,7 +1826,7 @@ mod linux_errqueue {
                     } else {
                         panic!("Expected some error origin");
                     }
-                    return *ext_err
+                    *ext_err
                 } else {
                     panic!("Unexpected control message {:?}", cmsg);
                 }
@@ -1884,7 +1872,7 @@ mod linux_errqueue {
                     } else {
                         panic!("Expected some error origin");
                     }
-                    return *ext_err
+                    *ext_err
                 } else {
                     panic!("Unexpected control message {:?}", cmsg);
                 }
diff --git a/test/test_dir.rs b/test/test_dir.rs
index 0dc7308e..2940b6ea 100644
--- a/test/test_dir.rs
+++ b/test/test_dir.rs
@@ -17,6 +17,7 @@ fn flags() -> OFlag {
 }
 
 #[test]
+#[allow(clippy::unnecessary_sort_by)]   // False positive
 fn read() {
     let tmp = tempdir().unwrap();
     File::create(&tmp.path().join("foo")).unwrap();
diff --git a/test/test_fcntl.rs b/test/test_fcntl.rs
index c19a1b0a..76252e6e 100644
--- a/test/test_fcntl.rs
+++ b/test/test_fcntl.rs
@@ -127,14 +127,14 @@ fn test_renameat2_exchange() {
     let old_path = old_dir.path().join("old");
     {
         let mut old_f = File::create(&old_path).unwrap();
-        old_f.write(b"old").unwrap();
+        old_f.write_all(b"old").unwrap();
     }
     let new_dir = tempfile::tempdir().unwrap();
     let new_dirfd = open(new_dir.path(), OFlag::empty(), Mode::empty()).unwrap();
     let new_path = new_dir.path().join("new");
     {
         let mut new_f = File::create(&new_path).unwrap();
-        new_f.write(b"new").unwrap();
+        new_f.write_all(b"new").unwrap();
     }
     renameat2(
         Some(old_dirfd),
@@ -319,9 +319,10 @@ mod linux_android {
 
         let buf1 = b"abcdef";
         let buf2 = b"defghi";
-        let mut iovecs = Vec::with_capacity(2);
-        iovecs.push(IoVec::from_slice(&buf1[0..3]));
-        iovecs.push(IoVec::from_slice(&buf2[0..3]));
+        let iovecs = vec![
+            IoVec::from_slice(&buf1[0..3]),
+            IoVec::from_slice(&buf2[0..3])
+        ];
 
         let res = vmsplice(wr, &iovecs[..], SpliceFFlags::empty()).unwrap();
 
diff --git a/test/test_kmod/mod.rs b/test/test_kmod/mod.rs
index e53e7a9e..0f7fc48e 100644
--- a/test/test_kmod/mod.rs
+++ b/test/test_kmod/mod.rs
@@ -34,7 +34,6 @@ fn compile_kernel_module() -> (PathBuf, String, TempDir) {
 use nix::errno::Errno;
 use nix::kmod::{delete_module, DeleteModuleFlags};
 use nix::kmod::{finit_module, init_module, ModuleInitFlags};
-use nix::Error;
 use std::ffi::CString;
 use std::fs::File;
 use std::io::Read;
@@ -90,7 +89,7 @@ fn test_init_and_delete_module() {
     let mut contents: Vec<u8> = Vec::new();
     f.read_to_end(&mut contents)
         .expect("unable to read kernel module content to buffer");
-    init_module(&mut contents, &CString::new("").unwrap()).expect("unable to load kernel module");
+    init_module(&contents, &CString::new("").unwrap()).expect("unable to load kernel module");
 
     delete_module(
         &CString::new(kmod_name).unwrap(),
@@ -110,7 +109,7 @@ fn test_init_and_delete_module_with_params() {
     let mut contents: Vec<u8> = Vec::new();
     f.read_to_end(&mut contents)
         .expect("unable to read kernel module content to buffer");
-    init_module(&mut contents, &CString::new("who=Nix number=2015").unwrap())
+    init_module(&contents, &CString::new("who=Nix number=2015").unwrap())
         .expect("unable to load kernel module");
 
     delete_module(
@@ -130,7 +129,7 @@ fn test_finit_module_invalid() {
     let f = File::open(kmod_path).expect("unable to open kernel module");
     let result = finit_module(&f, &CString::new("").unwrap(), ModuleInitFlags::empty());
 
-    assert_eq!(result.unwrap_err(), Error::from(Errno::EINVAL));
+    assert_eq!(result.unwrap_err(), Errno::EINVAL);
 }
 
 #[test]
@@ -147,7 +146,7 @@ fn test_finit_module_twice_and_delete_module() {
 
     let result = finit_module(&f, &CString::new("").unwrap(), ModuleInitFlags::empty());
 
-    assert_eq!(result.unwrap_err(), Error::from(Errno::EEXIST));
+    assert_eq!(result.unwrap_err(), Errno::EEXIST);
 
     delete_module(
         &CString::new(kmod_name).unwrap(),
@@ -163,5 +162,5 @@ fn test_delete_module_not_loaded() {
 
     let result = delete_module(&CString::new("hello").unwrap(), DeleteModuleFlags::empty());
 
-    assert_eq!(result.unwrap_err(), Error::from(Errno::ENOENT));
+    assert_eq!(result.unwrap_err(), Errno::ENOENT);
 }
diff --git a/test/test_mount.rs b/test/test_mount.rs
index c1b6c8a3..44287f97 100644
--- a/test/test_mount.rs
+++ b/test/test_mount.rs
@@ -21,14 +21,13 @@ mod test_mount {
     use nix::sys::stat::{self, Mode};
     use nix::unistd::getuid;
 
-    use tempfile;
-
-    static SCRIPT_CONTENTS: &'static [u8] = b"#!/bin/sh
+    static SCRIPT_CONTENTS: &[u8] = b"#!/bin/sh
 exit 23";
 
     const EXPECTED_STATUS: i32 = 23;
 
     const NONE: Option<&'static [u8]> = None;
+    #[allow(clippy::bind_instead_of_map)]   // False positive
     pub fn test_mount_tmpfs_without_flags_allows_rwx() {
         let tempdir = tempfile::tempdir().unwrap();
 
diff --git a/test/test_pty.rs b/test/test_pty.rs
index 52b63342..57874de3 100644
--- a/test/test_pty.rs
+++ b/test/test_pty.rs
@@ -114,6 +114,8 @@ fn open_ptty_pair() -> (PtyMaster, File) {
     let slave_fd = open(Path::new(&slave_name), OFlag::O_RDWR, stat::Mode::empty()).unwrap();
 
     #[cfg(target_os = "illumos")]
+    // TODO: rewrite using ioctl! 
+    #[allow(clippy::comparison_chain)]
     {
         use libc::{ioctl, I_FIND, I_PUSH};
 
diff --git a/test/test_stat.rs b/test/test_stat.rs
index 922c25fd..33cf748d 100644
--- a/test/test_stat.rs
+++ b/test/test_stat.rs
@@ -59,6 +59,7 @@ fn assert_stat_results(stat_result: Result<FileStat>) {
 #[cfg(not(any(target_os = "netbsd", target_os = "redox")))]
 // (Android's st_blocks is ulonglong which is always non-negative.)
 #[cfg_attr(target_os = "android", allow(unused_comparisons))]
+#[allow(clippy::absurd_extreme_comparisons)]    // Not absurd on all OSes
 fn assert_lstat_results(stat_result: Result<FileStat>) {
     let stats = stat_result.expect("stat call failed");
     assert!(stats.st_dev > 0);      // must be positive integer, exact number machine dependent
diff --git a/test/test_unistd.rs b/test/test_unistd.rs
index cb23ba75..3a3d49dd 100644
--- a/test/test_unistd.rs
+++ b/test/test_unistd.rs
@@ -10,7 +10,7 @@ use nix::sys::stat::{self, Mode, SFlag};
 #[cfg(not(any(target_os = "redox", target_os = "fuchsia")))]
 use nix::pty::{posix_openpt, grantpt, unlockpt, ptsname};
 use nix::errno::Errno;
-use std::{env, iter};
+use std::env;
 #[cfg(not(any(target_os = "fuchsia", target_os = "redox")))]
 use std::ffi::CString;
 #[cfg(not(target_os = "redox"))]
@@ -443,7 +443,7 @@ fn test_getcwd() {
     // 4096 on linux, 1024 on macos)
     let mut inner_tmp_dir = tmpdir_path;
     for _ in 0..5 {
-        let newdir = iter::repeat("a").take(100).collect::<String>();
+        let newdir = "a".repeat(100);
         inner_tmp_dir.push(newdir);
         assert!(mkdir(inner_tmp_dir.as_path(), Mode::S_IRWXU).is_ok());
     }
@@ -1051,7 +1051,7 @@ fn test_setfsuid() {
     dbg!(&temp_path);
     let temp_path_2 = (&temp_path).to_path_buf();
     let mut permissions = fs::metadata(&temp_path).unwrap().permissions();
-    permissions.set_mode(640);
+    permissions.set_mode(0o640);
 
     // spawn a new thread where to test setfsuid
     thread::spawn(move || {