More implementations of Write for immutable refs

Fixes #73836

Author: Federico Ponzi

library/std/src/io/stdio.rs

@@ -606,6 +606,33 @@ impl Write for Stdout {
         self.lock().write_fmt(args)
     }
 }
+
+#[stable(feature = "write_mt", since = "1.47.0")]
+impl Write for &Stdout {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        self.lock().write(buf)
+    }
+    fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
+        self.lock().write_vectored(bufs)
+    }
+    #[inline]
+    fn is_write_vectored(&self) -> bool {
+        self.lock().is_write_vectored()
+    }
+    fn flush(&mut self) -> io::Result<()> {
+        self.lock().flush()
+    }
+    fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
+        self.lock().write_all(buf)
+    }
+    fn write_all_vectored(&mut self, bufs: &mut [IoSlice<'_>]) -> io::Result<()> {
+        self.lock().write_all_vectored(bufs)
+    }
+    fn write_fmt(&mut self, args: fmt::Arguments<'_>) -> io::Result<()> {
+        self.lock().write_fmt(args)
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl Write for StdoutLock<'_> {
     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
@@ -782,6 +809,33 @@ impl Write for Stderr {
         self.lock().write_fmt(args)
     }
 }
+
+#[stable(feature = "write_mt", since = "1.47.0")]
+impl Write for &Stderr {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        self.lock().write(buf)
+    }
+    fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
+        self.lock().write_vectored(bufs)
+    }
+    #[inline]
+    fn is_write_vectored(&self) -> bool {
+        self.lock().is_write_vectored()
+    }
+    fn flush(&mut self) -> io::Result<()> {
+        self.lock().flush()
+    }
+    fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
+        self.lock().write_all(buf)
+    }
+    fn write_all_vectored(&mut self, bufs: &mut [IoSlice<'_>]) -> io::Result<()> {
+        self.lock().write_all_vectored(bufs)
+    }
+    fn write_fmt(&mut self, args: fmt::Arguments<'_>) -> io::Result<()> {
+        self.lock().write_fmt(args)
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl Write for StderrLock<'_> {
     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {

library/std/src/io/util.rs

@@ -248,6 +248,30 @@ impl Write for Sink {
     }
 }
 
+#[stable(feature = "write_mt", since = "1.47.0")]
+impl Write for &Sink {
+    #[inline]
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        Ok(buf.len())
+    }
+
+    #[inline]
+    fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
+        let total_len = bufs.iter().map(|b| b.len()).sum();
+        Ok(total_len)
+    }
+
+    #[inline]
+    fn is_write_vectored(&self) -> bool {
+        true
+    }
+
+    #[inline]
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+}
+
 #[stable(feature = "std_debug", since = "1.16.0")]
 impl fmt::Debug for Sink {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {

library/std/src/process.rs

@@ -262,6 +262,25 @@ impl Write for ChildStdin {
     }
 }
 
+#[stable(feature = "write_mt", since = "1.47.0")]
+impl Write for &ChildStdin {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        self.inner.write(buf)
+    }
+
+    fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
+        self.inner.write_vectored(bufs)
+    }
+
+    fn is_write_vectored(&self) -> bool {
+        self.inner.is_write_vectored()
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+}
+
 impl AsInner<AnonPipe> for ChildStdin {
     fn as_inner(&self) -> &AnonPipe {
         &self.inner