From e77b14e2acc1efbd649990873a8db678cf2086fa Mon Sep 17 00:00:00 2001
From: Maybe Waffle <waffle.lapkin@gmail.com>
Date: Mon, 1 May 2023 17:17:05 +0000
Subject: [PATCH] Relax implicit `R: Sized` bound on `BufReader<R>`

---
 library/std/src/io/buffered/bufreader.rs | 27 +++++++++++++-----------
 library/std/src/io/mod.rs                |  2 +-
 library/std/src/sys/unix/kernel_copy.rs  |  2 +-
 3 files changed, 17 insertions(+), 14 deletions(-)

diff --git a/library/std/src/io/buffered/bufreader.rs b/library/std/src/io/buffered/bufreader.rs
index 4f339a18a48..3edf9d747ce 100644
--- a/library/std/src/io/buffered/bufreader.rs
+++ b/library/std/src/io/buffered/bufreader.rs
@@ -47,9 +47,9 @@
 /// }
 /// ```
 #[stable(feature = "rust1", since = "1.0.0")]
-pub struct BufReader<R> {
-    inner: R,
+pub struct BufReader<R: ?Sized> {
     buf: Buffer,
+    inner: R,
 }
 
 impl<R: Read> BufReader<R> {
@@ -95,7 +95,7 @@ pub fn with_capacity(capacity: usize, inner: R) -> BufReader<R> {
     }
 }
 
-impl<R> BufReader<R> {
+impl<R: ?Sized> BufReader<R> {
     /// Gets a reference to the underlying reader.
     ///
     /// It is inadvisable to directly read from the underlying reader.
@@ -213,7 +213,10 @@ pub fn capacity(&self) -> usize {
     /// }
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn into_inner(self) -> R {
+    pub fn into_inner(self) -> R
+    where
+        R: Sized,
+    {
         self.inner
     }
 
@@ -226,13 +229,13 @@ fn discard_buffer(&mut self) {
 
 // This is only used by a test which asserts that the initialization-tracking is correct.
 #[cfg(test)]
-impl<R> BufReader<R> {
+impl<R: ?Sized> BufReader<R> {
     pub fn initialized(&self) -> usize {
         self.buf.initialized()
     }
 }
 
-impl<R: Seek> BufReader<R> {
+impl<R: ?Sized + Seek> BufReader<R> {
     /// Seeks relative to the current position. If the new position lies within the buffer,
     /// the buffer will not be flushed, allowing for more efficient seeks.
     /// This method does not return the location of the underlying reader, so the caller
@@ -257,7 +260,7 @@ pub fn seek_relative(&mut self, offset: i64) -> io::Result<()> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<R: Read> Read for BufReader<R> {
+impl<R: ?Sized + Read> Read for BufReader<R> {
     fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
         // If we don't have any buffered data and we're doing a massive read
         // (larger than our internal buffer), bypass our internal buffer
@@ -371,7 +374,7 @@ fn read_to_string(&mut self, buf: &mut String) -> io::Result<usize> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<R: Read> BufRead for BufReader<R> {
+impl<R: ?Sized + Read> BufRead for BufReader<R> {
     fn fill_buf(&mut self) -> io::Result<&[u8]> {
         self.buf.fill_buf(&mut self.inner)
     }
@@ -384,11 +387,11 @@ fn consume(&mut self, amt: usize) {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<R> fmt::Debug for BufReader<R>
 where
-    R: fmt::Debug,
+    R: ?Sized + fmt::Debug,
 {
     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
         fmt.debug_struct("BufReader")
-            .field("reader", &self.inner)
+            .field("reader", &&self.inner)
             .field(
                 "buffer",
                 &format_args!("{}/{}", self.buf.filled() - self.buf.pos(), self.capacity()),
@@ -398,7 +401,7 @@ fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<R: Seek> Seek for BufReader<R> {
+impl<R: ?Sized + Seek> Seek for BufReader<R> {
     /// Seek to an offset, in bytes, in the underlying reader.
     ///
     /// The position used for seeking with <code>[SeekFrom::Current]\(_)</code> is the
@@ -491,7 +494,7 @@ fn stream_position(&mut self) -> io::Result<u64> {
     }
 }
 
-impl<T> SizeHint for BufReader<T> {
+impl<T: ?Sized> SizeHint for BufReader<T> {
     #[inline]
     fn lower_bound(&self) -> usize {
         SizeHint::lower_bound(self.get_ref()) + self.buffer().len()
diff --git a/library/std/src/io/mod.rs b/library/std/src/io/mod.rs
index 9e09ce337bc..bb329dc2446 100644
--- a/library/std/src/io/mod.rs
+++ b/library/std/src/io/mod.rs
@@ -2753,7 +2753,7 @@ fn size_hint(&self) -> (usize, Option<usize>) {
     }
 }
 
-impl<T> SizeHint for T {
+impl<T: ?Sized> SizeHint for T {
     #[inline]
     default fn lower_bound(&self) -> usize {
         0
diff --git a/library/std/src/sys/unix/kernel_copy.rs b/library/std/src/sys/unix/kernel_copy.rs
index 16c8e0c0ebf..81b081e0070 100644
--- a/library/std/src/sys/unix/kernel_copy.rs
+++ b/library/std/src/sys/unix/kernel_copy.rs
@@ -466,7 +466,7 @@ fn properties(&self) -> CopyParams {
     }
 }
 
-impl<T: CopyRead> CopyRead for BufReader<T> {
+impl<T: ?Sized + CopyRead> CopyRead for BufReader<T> {
     fn drain_to<W: Write>(&mut self, writer: &mut W, outer_limit: u64) -> Result<u64> {
         let buf = self.buffer();
         let buf = &buf[0..min(buf.len(), outer_limit.try_into().unwrap_or(usize::MAX))];