Rollup merge of rust-lang#67807 - lzutao:toilet-closure, r=Centril

Use drop instead of the toilet closure `|_| ()`

Author: JohnTitor

src/liballoc/tests/arc.rs

@@ -142,7 +142,7 @@ fn shared_from_iter_trustedlen_normal() {
 
     // Try a ZST to make sure it is handled well.
     {
-        let iter = (0..SHARED_ITER_MAX).map(|_| ());
+        let iter = (0..SHARED_ITER_MAX).map(drop);
         let vec = iter.clone().collect::<Vec<_>>();
         let rc = iter.collect::<Rc<[_]>>();
         assert_eq!(&*vec, &*rc);

src/liballoc/tests/rc.rs

@@ -138,7 +138,7 @@ fn shared_from_iter_trustedlen_normal() {
 
     // Try a ZST to make sure it is handled well.
     {
-        let iter = (0..SHARED_ITER_MAX).map(|_| ());
+        let iter = (0..SHARED_ITER_MAX).map(drop);
         let vec = iter.clone().collect::<Vec<_>>();
         let rc = iter.collect::<Rc<[_]>>();
         assert_eq!(&*vec, &*rc);

src/librustc_parse/parser/diagnostics.rs

@@ -848,7 +848,7 @@ impl<'a> Parser<'a> {
         let appl = Applicability::MachineApplicable;
         if self.token.span == DUMMY_SP || self.prev_span == DUMMY_SP {
             // Likely inside a macro, can't provide meaninful suggestions.
-            return self.expect(&token::Semi).map(|_| ());
+            return self.expect(&token::Semi).map(drop);
         } else if !sm.is_multiline(self.prev_span.until(self.token.span)) {
             // The current token is in the same line as the prior token, not recoverable.
         } else if self.look_ahead(1, |t| {
@@ -887,7 +887,7 @@ impl<'a> Parser<'a> {
                 .emit();
             return Ok(());
         }
-        self.expect(&token::Semi).map(|_| ()) // Error unconditionally
+        self.expect(&token::Semi).map(drop) // Error unconditionally
     }
 
     pub(super) fn parse_semi_or_incorrect_foreign_fn_body(

src/libstd/io/buffered.rs

@@ -232,7 +232,7 @@ impl<R: Seek> BufReader<R> {
                 }
             }
         }
-        self.seek(SeekFrom::Current(offset)).map(|_| ())
+        self.seek(SeekFrom::Current(offset)).map(drop)
     }
 }
 

src/libstd/sys/unix/android.rs

@@ -93,12 +93,12 @@ pub fn ftruncate64(fd: c_int, size: u64) -> io::Result<()> {
 
     unsafe {
         match ftruncate64.get() {
-            Some(f) => cvt_r(|| f(fd, size as i64)).map(|_| ()),
+            Some(f) => cvt_r(|| f(fd, size as i64)).map(drop),
             None => {
                 if size > i32::max_value() as u64 {
                     Err(io::Error::new(io::ErrorKind::InvalidInput, "cannot truncate >2GB"))
                 } else {
-                    cvt_r(|| ftruncate(fd, size as i32)).map(|_| ())
+                    cvt_r(|| ftruncate(fd, size as i32)).map(drop)
                 }
             }
         }
@@ -107,7 +107,7 @@ pub fn ftruncate64(fd: c_int, size: u64) -> io::Result<()> {
 
 #[cfg(target_pointer_width = "64")]
 pub fn ftruncate64(fd: c_int, size: u64) -> io::Result<()> {
-    unsafe { cvt_r(|| ftruncate(fd, size as i64)).map(|_| ()) }
+    unsafe { cvt_r(|| ftruncate(fd, size as i64)).map(drop) }
 }
 
 #[cfg(target_pointer_width = "32")]

src/libstd/sys/unix/fs.rs

@@ -814,7 +814,7 @@ impl File {
             use crate::convert::TryInto;
             let size: off64_t =
                 size.try_into().map_err(|e| io::Error::new(io::ErrorKind::InvalidInput, e))?;
-            cvt_r(|| unsafe { ftruncate64(self.0.raw(), size) }).map(|_| ())
+            cvt_r(|| unsafe { ftruncate64(self.0.raw(), size) }).map(drop)
         }
     }
 

src/libstd/sys/unix/net.rs

@@ -324,7 +324,7 @@ impl Socket {
 
     pub fn set_nonblocking(&self, nonblocking: bool) -> io::Result<()> {
         let mut nonblocking = nonblocking as libc::c_int;
-        cvt(unsafe { libc::ioctl(*self.as_inner(), libc::FIONBIO, &mut nonblocking) }).map(|_| ())
+        cvt(unsafe { libc::ioctl(*self.as_inner(), libc::FIONBIO, &mut nonblocking) }).map(drop)
     }
 
     pub fn take_error(&self) -> io::Result<Option<io::Error>> {

src/libstd/sys/unix/os.rs

@@ -529,7 +529,7 @@ pub fn setenv(k: &OsStr, v: &OsStr) -> io::Result<()> {
 
     unsafe {
         let _guard = env_lock();
-        cvt(libc::setenv(k.as_ptr(), v.as_ptr(), 1)).map(|_| ())
+        cvt(libc::setenv(k.as_ptr(), v.as_ptr(), 1)).map(drop)
     }
 }
 
@@ -538,7 +538,7 @@ pub fn unsetenv(n: &OsStr) -> io::Result<()> {
 
     unsafe {
         let _guard = env_lock();
-        cvt(libc::unsetenv(nbuf.as_ptr())).map(|_| ())
+        cvt(libc::unsetenv(nbuf.as_ptr())).map(drop)
     }
 }
 

src/libstd/sys/unix/pipe.rs

@@ -99,11 +99,11 @@ pub fn read2(p1: AnonPipe, v1: &mut Vec<u8>, p2: AnonPipe, v2: &mut Vec<u8>) ->
 
         if fds[0].revents != 0 && read(&p1, v1)? {
             p2.set_nonblocking(false)?;
-            return p2.read_to_end(v2).map(|_| ());
+            return p2.read_to_end(v2).map(drop);
         }
         if fds[1].revents != 0 && read(&p2, v2)? {
             p1.set_nonblocking(false)?;
-            return p1.read_to_end(v1).map(|_| ());
+            return p1.read_to_end(v1).map(drop);
         }
     }
 

src/libstd/sys/unix/process/process_unix.rs

@@ -425,7 +425,7 @@ impl Process {
                 "invalid argument: can't kill an exited process",
             ))
         } else {
-            cvt(unsafe { libc::kill(self.pid, libc::SIGKILL) }).map(|_| ())
+            cvt(unsafe { libc::kill(self.pid, libc::SIGKILL) }).map(drop)
         }
     }