Added W: Writer bound to BufferedWriter<W> to avoid specialized Drop impl.

Author: pnkfelix

src/libstd/old_io/buffered.rs

@@ -148,14 +148,14 @@ impl<R: Reader> Reader for BufferedReader<R> {
 /// writer.write_str("hello, world").unwrap();
 /// writer.flush().unwrap();
 /// ```
-pub struct BufferedWriter<W> {
+pub struct BufferedWriter<W: Writer> {
     inner: Option<W>,
     buf: Vec<u8>,
     pos: uint
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<W> fmt::Debug for BufferedWriter<W> where W: fmt::Debug {
+impl<W: Writer> fmt::Debug for BufferedWriter<W> where W: fmt::Debug {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
         write!(fmt, "BufferedWriter {{ writer: {:?}, buffer: {}/{} }}",
                self.inner.as_ref().unwrap(), self.pos, self.buf.len())
@@ -250,12 +250,12 @@ impl<W: Writer> Drop for BufferedWriter<W> {
 /// `'\n'`) is detected.
 ///
 /// This writer will be flushed when it is dropped.
-pub struct LineBufferedWriter<W> {
+pub struct LineBufferedWriter<W: Writer> {
     inner: BufferedWriter<W>,
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<W> fmt::Debug for LineBufferedWriter<W> where W: fmt::Debug {
+impl<W: Writer> fmt::Debug for LineBufferedWriter<W> where W: fmt::Debug {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
         write!(fmt, "LineBufferedWriter {{ writer: {:?}, buffer: {}/{} }}",
                self.inner.inner, self.inner.pos, self.inner.buf.len())
@@ -299,16 +299,16 @@ impl<W: Writer> Writer for LineBufferedWriter<W> {
     fn flush(&mut self) -> IoResult<()> { self.inner.flush() }
 }
 
-struct InternalBufferedWriter<W>(BufferedWriter<W>);
+struct InternalBufferedWriter<W: Writer>(BufferedWriter<W>);
 
-impl<W> InternalBufferedWriter<W> {
+impl<W: Writer> InternalBufferedWriter<W> {
     fn get_mut<'a>(&'a mut self) -> &'a mut BufferedWriter<W> {
         let InternalBufferedWriter(ref mut w) = *self;
         return w;
     }
 }
 
-impl<W: Reader> Reader for InternalBufferedWriter<W> {
+impl<W: Reader + Writer> Reader for InternalBufferedWriter<W> {
     fn read(&mut self, buf: &mut [u8]) -> IoResult<uint> {
         self.get_mut().inner.as_mut().unwrap().read(buf)
     }
@@ -343,12 +343,12 @@ impl<W: Reader> Reader for InternalBufferedWriter<W> {
 ///     Err(e) => println!("error reading: {}", e)
 /// }
 /// ```
-pub struct BufferedStream<S> {
+pub struct BufferedStream<S: Writer> {
     inner: BufferedReader<InternalBufferedWriter<S>>
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<S> fmt::Debug for BufferedStream<S> where S: fmt::Debug {
+impl<S: Writer> fmt::Debug for BufferedStream<S> where S: fmt::Debug {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
         let reader = &self.inner;
         let writer = &self.inner.inner.0;