Relax implicit `W: Sized` bound on `LineWriter<W>`

2 files changed, 29 insertions, 27 deletions

diff --git a/library/std/src/io/buffered/linewriter.rs b/library/std/src/io/buffered/linewriter.rs
index a26a4ab330e..3d4ae704193 100644
--- a/library/std/src/io/buffered/linewriter.rs
+++ b/library/std/src/io/buffered/linewriter.rs
@@ -64,7 +64,7 @@ use crate::io::{self, buffered::LineWriterShim, BufWriter, IntoInnerError, IoSli
 /// }
 /// ```
 #[stable(feature = "rust1", since = "1.0.0")]
-pub struct LineWriter<W: Write> {
+pub struct LineWriter<W: ?Sized + Write> {
     inner: BufWriter<W>,
 }
 
@@ -109,27 +109,6 @@ impl<W: Write> LineWriter<W> {
         LineWriter { inner: BufWriter::with_capacity(capacity, inner) }
     }
 
-    /// Gets a reference to the underlying writer.
-    ///
-    /// # Examples
-    ///
-    /// ```no_run
-    /// use std::fs::File;
-    /// use std::io::LineWriter;
-    ///
-    /// fn main() -> std::io::Result<()> {
-    ///     let file = File::create("poem.txt")?;
-    ///     let file = LineWriter::new(file);
-    ///
-    ///     let reference = file.get_ref();
-    ///     Ok(())
-    /// }
-    /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn get_ref(&self) -> &W {
-        self.inner.get_ref()
-    }
-
     /// Gets a mutable reference to the underlying writer.
     ///
     /// Caution must be taken when calling methods on the mutable reference
@@ -184,8 +163,31 @@ impl<W: Write> LineWriter<W> {
     }
 }
 
+impl<W: ?Sized + Write> LineWriter<W> {
+    /// Gets a reference to the underlying writer.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use std::fs::File;
+    /// use std::io::LineWriter;
+    ///
+    /// fn main() -> std::io::Result<()> {
+    ///     let file = File::create("poem.txt")?;
+    ///     let file = LineWriter::new(file);
+    ///
+    ///     let reference = file.get_ref();
+    ///     Ok(())
+    /// }
+    /// ```
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn get_ref(&self) -> &W {
+        self.inner.get_ref()
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<W: Write> Write for LineWriter<W> {
+impl<W: ?Sized + Write> Write for LineWriter<W> {
     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
         LineWriterShim::new(&mut self.inner).write(buf)
     }
@@ -216,7 +218,7 @@ impl<W: Write> Write for LineWriter<W> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<W: Write> fmt::Debug for LineWriter<W>
+impl<W: ?Sized + Write> fmt::Debug for LineWriter<W>
 where
     W: fmt::Debug,
 {
diff --git a/library/std/src/io/buffered/linewritershim.rs b/library/std/src/io/buffered/linewritershim.rs
index 0175d2693e8..f2a55da05b2 100644
--- a/library/std/src/io/buffered/linewritershim.rs
+++ b/library/std/src/io/buffered/linewritershim.rs
@@ -11,11 +11,11 @@ use crate::sys_common::memchr;
 /// `BufWriters` to be temporarily given line-buffering logic; this is what
 /// enables Stdout to be alternately in line-buffered or block-buffered mode.
 #[derive(Debug)]
-pub struct LineWriterShim<'a, W: Write> {
+pub struct LineWriterShim<'a, W: ?Sized + Write> {
     buffer: &'a mut BufWriter<W>,
 }
 
-impl<'a, W: Write> LineWriterShim<'a, W> {
+impl<'a, W: ?Sized + Write> LineWriterShim<'a, W> {
     pub fn new(buffer: &'a mut BufWriter<W>) -> Self {
         Self { buffer }
     }
@@ -49,7 +49,7 @@ impl<'a, W: Write> LineWriterShim<'a, W> {
     }
 }
 
-impl<'a, W: Write> Write for LineWriterShim<'a, W> {
+impl<'a, W: ?Sized + Write> Write for LineWriterShim<'a, W> {
     /// Write some data into this BufReader with line buffering. This means
     /// that, if any newlines are present in the data, the data up to the last
     /// newline is sent directly to the underlying writer, and data after it