Rollup merge of #52732 - SimonSapin:spring, r=Mark-Simulacrum

Remove unstable and deprecated APIs

5 files changed, 0 insertions, 525 deletions

diff --git a/src/libstd/Cargo.toml b/src/libstd/Cargo.toml
index 5a2dce5930a..5348c9a0f34 100644
--- a/src/libstd/Cargo.toml
+++ b/src/libstd/Cargo.toml
@@ -22,7 +22,6 @@ core = { path = "../libcore" }
 libc = { path = "../rustc/libc_shim" }
 compiler_builtins = { path = "../rustc/compiler_builtins_shim" }
 profiler_builtins = { path = "../libprofiler_builtins", optional = true }
-std_unicode = { path = "../libstd_unicode" }
 unwind = { path = "../libunwind" }
 
 [dev-dependencies]
diff --git a/src/libstd/ascii.rs b/src/libstd/ascii.rs
index 37641067734..0c8e95aa426 100644
--- a/src/libstd/ascii.rs
+++ b/src/libstd/ascii.rs
@@ -154,180 +154,6 @@ pub trait AsciiExt {
     /// [`to_ascii_lowercase`]: #tymethod.to_ascii_lowercase
     #[stable(feature = "ascii", since = "1.9.0")]
     fn make_ascii_lowercase(&mut self);
-
-    /// Checks if the value is an ASCII alphabetic character:
-    /// U+0041 'A' ... U+005A 'Z' or U+0061 'a' ... U+007A 'z'.
-    /// For strings, true if all characters in the string are
-    /// ASCII alphabetic.
-    ///
-    /// # Note
-    ///
-    /// This method will be deprecated in favor of the identically-named
-    /// inherent methods on `u8` and `char`.
-    /// For `[u8]` use `.iter().all(u8::is_ascii_alphabetic)`.
-    /// For `str` use `.bytes().all(u8::is_ascii_alphabetic)`.
-    #[unstable(feature = "ascii_ctype", issue = "39658")]
-    #[rustc_deprecated(since = "1.26.0", reason = "use inherent methods instead")]
-    fn is_ascii_alphabetic(&self) -> bool { unimplemented!(); }
-
-    /// Checks if the value is an ASCII uppercase character:
-    /// U+0041 'A' ... U+005A 'Z'.
-    /// For strings, true if all characters in the string are
-    /// ASCII uppercase.
-    ///
-    /// # Note
-    ///
-    /// This method will be deprecated in favor of the identically-named
-    /// inherent methods on `u8` and `char`.
-    /// For `[u8]` use `.iter().all(u8::is_ascii_uppercase)`.
-    /// For `str` use `.bytes().all(u8::is_ascii_uppercase)`.
-    #[unstable(feature = "ascii_ctype", issue = "39658")]
-    #[rustc_deprecated(since = "1.26.0", reason = "use inherent methods instead")]
-    fn is_ascii_uppercase(&self) -> bool { unimplemented!(); }
-
-    /// Checks if the value is an ASCII lowercase character:
-    /// U+0061 'a' ... U+007A 'z'.
-    /// For strings, true if all characters in the string are
-    /// ASCII lowercase.
-    ///
-    /// # Note
-    ///
-    /// This method will be deprecated in favor of the identically-named
-    /// inherent methods on `u8` and `char`.
-    /// For `[u8]` use `.iter().all(u8::is_ascii_lowercase)`.
-    /// For `str` use `.bytes().all(u8::is_ascii_lowercase)`.
-    #[unstable(feature = "ascii_ctype", issue = "39658")]
-    #[rustc_deprecated(since = "1.26.0", reason = "use inherent methods instead")]
-    fn is_ascii_lowercase(&self) -> bool { unimplemented!(); }
-
-    /// Checks if the value is an ASCII alphanumeric character:
-    /// U+0041 'A' ... U+005A 'Z', U+0061 'a' ... U+007A 'z', or
-    /// U+0030 '0' ... U+0039 '9'.
-    /// For strings, true if all characters in the string are
-    /// ASCII alphanumeric.
-    ///
-    /// # Note
-    ///
-    /// This method will be deprecated in favor of the identically-named
-    /// inherent methods on `u8` and `char`.
-    /// For `[u8]` use `.iter().all(u8::is_ascii_alphanumeric)`.
-    /// For `str` use `.bytes().all(u8::is_ascii_alphanumeric)`.
-    #[unstable(feature = "ascii_ctype", issue = "39658")]
-    #[rustc_deprecated(since = "1.26.0", reason = "use inherent methods instead")]
-    fn is_ascii_alphanumeric(&self) -> bool { unimplemented!(); }
-
-    /// Checks if the value is an ASCII decimal digit:
-    /// U+0030 '0' ... U+0039 '9'.
-    /// For strings, true if all characters in the string are
-    /// ASCII digits.
-    ///
-    /// # Note
-    ///
-    /// This method will be deprecated in favor of the identically-named
-    /// inherent methods on `u8` and `char`.
-    /// For `[u8]` use `.iter().all(u8::is_ascii_digit)`.
-    /// For `str` use `.bytes().all(u8::is_ascii_digit)`.
-    #[unstable(feature = "ascii_ctype", issue = "39658")]
-    #[rustc_deprecated(since = "1.26.0", reason = "use inherent methods instead")]
-    fn is_ascii_digit(&self) -> bool { unimplemented!(); }
-
-    /// Checks if the value is an ASCII hexadecimal digit:
-    /// U+0030 '0' ... U+0039 '9', U+0041 'A' ... U+0046 'F', or
-    /// U+0061 'a' ... U+0066 'f'.
-    /// For strings, true if all characters in the string are
-    /// ASCII hex digits.
-    ///
-    /// # Note
-    ///
-    /// This method will be deprecated in favor of the identically-named
-    /// inherent methods on `u8` and `char`.
-    /// For `[u8]` use `.iter().all(u8::is_ascii_hexdigit)`.
-    /// For `str` use `.bytes().all(u8::is_ascii_hexdigit)`.
-    #[unstable(feature = "ascii_ctype", issue = "39658")]
-    #[rustc_deprecated(since = "1.26.0", reason = "use inherent methods instead")]
-    fn is_ascii_hexdigit(&self) -> bool { unimplemented!(); }
-
-    /// Checks if the value is an ASCII punctuation character:
-    ///
-    /// U+0021 ... U+002F `! " # $ % & ' ( ) * + , - . /`
-    /// U+003A ... U+0040 `: ; < = > ? @`
-    /// U+005B ... U+0060 ``[ \\ ] ^ _ ` ``
-    /// U+007B ... U+007E `{ | } ~`
-    ///
-    /// For strings, true if all characters in the string are
-    /// ASCII punctuation.
-    ///
-    /// # Note
-    ///
-    /// This method will be deprecated in favor of the identically-named
-    /// inherent methods on `u8` and `char`.
-    /// For `[u8]` use `.iter().all(u8::is_ascii_punctuation)`.
-    /// For `str` use `.bytes().all(u8::is_ascii_punctuation)`.
-    #[unstable(feature = "ascii_ctype", issue = "39658")]
-    #[rustc_deprecated(since = "1.26.0", reason = "use inherent methods instead")]
-    fn is_ascii_punctuation(&self) -> bool { unimplemented!(); }
-
-    /// Checks if the value is an ASCII graphic character:
-    /// U+0021 '!' ... U+007E '~'.
-    /// For strings, true if all characters in the string are
-    /// ASCII graphic characters.
-    ///
-    /// # Note
-    ///
-    /// This method will be deprecated in favor of the identically-named
-    /// inherent methods on `u8` and `char`.
-    /// For `[u8]` use `.iter().all(u8::is_ascii_graphic)`.
-    /// For `str` use `.bytes().all(u8::is_ascii_graphic)`.
-    #[unstable(feature = "ascii_ctype", issue = "39658")]
-    #[rustc_deprecated(since = "1.26.0", reason = "use inherent methods instead")]
-    fn is_ascii_graphic(&self) -> bool { unimplemented!(); }
-
-    /// Checks if the value is an ASCII whitespace character:
-    /// U+0020 SPACE, U+0009 HORIZONTAL TAB, U+000A LINE FEED,
-    /// U+000C FORM FEED, or U+000D CARRIAGE RETURN.
-    /// For strings, true if all characters in the string are
-    /// ASCII whitespace.
-    ///
-    /// Rust uses the WhatWG Infra Standard's [definition of ASCII
-    /// whitespace][infra-aw].  There are several other definitions in
-    /// wide use.  For instance, [the POSIX locale][pct] includes
-    /// U+000B VERTICAL TAB as well as all the above characters,
-    /// but—from the very same specification—[the default rule for
-    /// "field splitting" in the Bourne shell][bfs] considers *only*
-    /// SPACE, HORIZONTAL TAB, and LINE FEED as whitespace.
-    ///
-    /// If you are writing a program that will process an existing
-    /// file format, check what that format's definition of whitespace is
-    /// before using this function.
-    ///
-    /// [infra-aw]: https://infra.spec.whatwg.org/#ascii-whitespace
-    /// [pct]: http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap07.html#tag_07_03_01
-    /// [bfs]: http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_06_05
-    ///
-    /// # Note
-    ///
-    /// This method will be deprecated in favor of the identically-named
-    /// inherent methods on `u8` and `char`.
-    /// For `[u8]` use `.iter().all(u8::is_ascii_whitespace)`.
-    /// For `str` use `.bytes().all(u8::is_ascii_whitespace)`.
-    #[unstable(feature = "ascii_ctype", issue = "39658")]
-    #[rustc_deprecated(since = "1.26.0", reason = "use inherent methods instead")]
-    fn is_ascii_whitespace(&self) -> bool { unimplemented!(); }
-
-    /// Checks if the value is an ASCII control character:
-    /// U+0000 NUL ... U+001F UNIT SEPARATOR, or U+007F DELETE.
-    /// Note that most ASCII whitespace characters are control
-    /// characters, but SPACE is not.
-    ///
-    /// # Note
-    ///
-    /// This method will be deprecated in favor of the identically-named
-    /// inherent methods on `u8` and `char`.
-    /// For `[u8]` use `.iter().all(u8::is_ascii_control)`.
-    /// For `str` use `.bytes().all(u8::is_ascii_control)`.
-    #[unstable(feature = "ascii_ctype", issue = "39658")]
-    #[rustc_deprecated(since = "1.26.0", reason = "use inherent methods instead")]
-    fn is_ascii_control(&self) -> bool { unimplemented!(); }
 }
 
 macro_rules! delegating_ascii_methods {
@@ -352,47 +178,12 @@ macro_rules! delegating_ascii_methods {
     }
 }
 
-macro_rules! delegating_ascii_ctype_methods {
-    () => {
-        #[inline]
-        fn is_ascii_alphabetic(&self) -> bool { self.is_ascii_alphabetic() }
-
-        #[inline]
-        fn is_ascii_uppercase(&self) -> bool { self.is_ascii_uppercase() }
-
-        #[inline]
-        fn is_ascii_lowercase(&self) -> bool { self.is_ascii_lowercase() }
-
-        #[inline]
-        fn is_ascii_alphanumeric(&self) -> bool { self.is_ascii_alphanumeric() }
-
-        #[inline]
-        fn is_ascii_digit(&self) -> bool { self.is_ascii_digit() }
-
-        #[inline]
-        fn is_ascii_hexdigit(&self) -> bool { self.is_ascii_hexdigit() }
-
-        #[inline]
-        fn is_ascii_punctuation(&self) -> bool { self.is_ascii_punctuation() }
-
-        #[inline]
-        fn is_ascii_graphic(&self) -> bool { self.is_ascii_graphic() }
-
-        #[inline]
-        fn is_ascii_whitespace(&self) -> bool { self.is_ascii_whitespace() }
-
-        #[inline]
-        fn is_ascii_control(&self) -> bool { self.is_ascii_control() }
-    }
-}
-
 #[stable(feature = "rust1", since = "1.0.0")]
 #[allow(deprecated)]
 impl AsciiExt for u8 {
     type Owned = u8;
 
     delegating_ascii_methods!();
-    delegating_ascii_ctype_methods!();
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -401,7 +192,6 @@ impl AsciiExt for char {
     type Owned = char;
 
     delegating_ascii_methods!();
-    delegating_ascii_ctype_methods!();
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -410,56 +200,6 @@ impl AsciiExt for [u8] {
     type Owned = Vec<u8>;
 
     delegating_ascii_methods!();
-
-    #[inline]
-    fn is_ascii_alphabetic(&self) -> bool {
-        self.iter().all(|b| b.is_ascii_alphabetic())
-    }
-
-    #[inline]
-    fn is_ascii_uppercase(&self) -> bool {
-        self.iter().all(|b| b.is_ascii_uppercase())
-    }
-
-    #[inline]
-    fn is_ascii_lowercase(&self) -> bool {
-        self.iter().all(|b| b.is_ascii_lowercase())
-    }
-
-    #[inline]
-    fn is_ascii_alphanumeric(&self) -> bool {
-        self.iter().all(|b| b.is_ascii_alphanumeric())
-    }
-
-    #[inline]
-    fn is_ascii_digit(&self) -> bool {
-        self.iter().all(|b| b.is_ascii_digit())
-    }
-
-    #[inline]
-    fn is_ascii_hexdigit(&self) -> bool {
-        self.iter().all(|b| b.is_ascii_hexdigit())
-    }
-
-    #[inline]
-    fn is_ascii_punctuation(&self) -> bool {
-        self.iter().all(|b| b.is_ascii_punctuation())
-    }
-
-    #[inline]
-    fn is_ascii_graphic(&self) -> bool {
-        self.iter().all(|b| b.is_ascii_graphic())
-    }
-
-    #[inline]
-    fn is_ascii_whitespace(&self) -> bool {
-        self.iter().all(|b| b.is_ascii_whitespace())
-    }
-
-    #[inline]
-    fn is_ascii_control(&self) -> bool {
-        self.iter().all(|b| b.is_ascii_control())
-    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -468,54 +208,4 @@ impl AsciiExt for str {
     type Owned = String;
 
     delegating_ascii_methods!();
-
-    #[inline]
-    fn is_ascii_alphabetic(&self) -> bool {
-        self.bytes().all(|b| b.is_ascii_alphabetic())
-    }
-
-    #[inline]
-    fn is_ascii_uppercase(&self) -> bool {
-        self.bytes().all(|b| b.is_ascii_uppercase())
-    }
-
-    #[inline]
-    fn is_ascii_lowercase(&self) -> bool {
-        self.bytes().all(|b| b.is_ascii_lowercase())
-    }
-
-    #[inline]
-    fn is_ascii_alphanumeric(&self) -> bool {
-        self.bytes().all(|b| b.is_ascii_alphanumeric())
-    }
-
-    #[inline]
-    fn is_ascii_digit(&self) -> bool {
-        self.bytes().all(|b| b.is_ascii_digit())
-    }
-
-    #[inline]
-    fn is_ascii_hexdigit(&self) -> bool {
-        self.bytes().all(|b| b.is_ascii_hexdigit())
-    }
-
-    #[inline]
-    fn is_ascii_punctuation(&self) -> bool {
-        self.bytes().all(|b| b.is_ascii_punctuation())
-    }
-
-    #[inline]
-    fn is_ascii_graphic(&self) -> bool {
-        self.bytes().all(|b| b.is_ascii_graphic())
-    }
-
-    #[inline]
-    fn is_ascii_whitespace(&self) -> bool {
-        self.bytes().all(|b| b.is_ascii_whitespace())
-    }
-
-    #[inline]
-    fn is_ascii_control(&self) -> bool {
-        self.bytes().all(|b| b.is_ascii_control())
-    }
 }
diff --git a/src/libstd/io/buffered.rs b/src/libstd/io/buffered.rs
index 2babf508fdc..03c97de6ec1 100644
--- a/src/libstd/io/buffered.rs
+++ b/src/libstd/io/buffered.rs
@@ -154,33 +154,6 @@ impl<R: Read> BufReader<R> {
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn get_mut(&mut self) -> &mut R { &mut self.inner }
 
-    /// Returns `true` if there are no bytes in the internal buffer.
-    ///
-    /// # Examples
-    //
-    /// ```no_run
-    /// # #![feature(bufreader_is_empty)]
-    /// use std::io::BufReader;
-    /// use std::io::BufRead;
-    /// use std::fs::File;
-    ///
-    /// fn main() -> std::io::Result<()> {
-    ///     let f1 = File::open("log.txt")?;
-    ///     let mut reader = BufReader::new(f1);
-    ///     assert!(reader.is_empty());
-    ///
-    ///     if reader.fill_buf()?.len() > 0 {
-    ///         assert!(!reader.is_empty());
-    ///     }
-    ///     Ok(())
-    /// }
-    /// ```
-    #[unstable(feature = "bufreader_is_empty", issue = "45323", reason = "recently added")]
-    #[rustc_deprecated(since = "1.26.0", reason = "use .buffer().is_empty() instead")]
-    pub fn is_empty(&self) -> bool {
-        self.buffer().is_empty()
-    }
-
     /// Returns a reference to the internally buffered data.
     ///
     /// Unlike `fill_buf`, this will not attempt to fill the buffer if it is empty.
@@ -1266,25 +1239,6 @@ mod tests {
     }
 
     #[test]
-    #[allow(deprecated)]
-    fn read_char_buffered() {
-        let buf = [195, 159];
-        let reader = BufReader::with_capacity(1, &buf[..]);
-        assert_eq!(reader.chars().next().unwrap().unwrap(), 'ß');
-    }
-
-    #[test]
-    #[allow(deprecated)]
-    fn test_chars() {
-        let buf = [195, 159, b'a'];
-        let reader = BufReader::with_capacity(1, &buf[..]);
-        let mut it = reader.chars();
-        assert_eq!(it.next().unwrap().unwrap(), 'ß');
-        assert_eq!(it.next().unwrap().unwrap(), 'a');
-        assert!(it.next().is_none());
-    }
-
-    #[test]
     #[should_panic]
     fn dont_panic_in_drop_on_panicked_flush() {
         struct FailFlushWriter;
diff --git a/src/libstd/io/cursor.rs b/src/libstd/io/cursor.rs
index 3622df16b9d..14f20151dca 100644
--- a/src/libstd/io/cursor.rs
+++ b/src/libstd/io/cursor.rs
@@ -551,26 +551,6 @@ mod tests {
     }
 
     #[test]
-    #[allow(deprecated)]
-    fn test_read_char() {
-        let b = &b"Vi\xE1\xBB\x87t"[..];
-        let mut c = Cursor::new(b).chars();
-        assert_eq!(c.next().unwrap().unwrap(), 'V');
-        assert_eq!(c.next().unwrap().unwrap(), 'i');
-        assert_eq!(c.next().unwrap().unwrap(), 'ệ');
-        assert_eq!(c.next().unwrap().unwrap(), 't');
-        assert!(c.next().is_none());
-    }
-
-    #[test]
-    #[allow(deprecated)]
-    fn test_read_bad_char() {
-        let b = &b"\x80"[..];
-        let mut c = Cursor::new(b).chars();
-        assert!(c.next().unwrap().is_err());
-    }
-
-    #[test]
     fn seek_past_end() {
         let buf = [0xff];
         let mut r = Cursor::new(&buf[..]);
diff --git a/src/libstd/io/mod.rs b/src/libstd/io/mod.rs
index 85304874848..5e89ad45f81 100644
--- a/src/libstd/io/mod.rs
+++ b/src/libstd/io/mod.rs
@@ -270,10 +270,7 @@
 #![stable(feature = "rust1", since = "1.0.0")]
 
 use cmp;
-use core::str as core_str;
-use error as std_error;
 use fmt;
-use result;
 use str;
 use memchr;
 use ptr;
@@ -800,53 +797,6 @@ pub trait Read {
         Bytes { inner: self }
     }
 
-    /// Transforms this `Read` instance to an [`Iterator`] over [`char`]s.
-    ///
-    /// This adaptor will attempt to interpret this reader as a UTF-8 encoded
-    /// sequence of characters. The returned iterator will return [`None`] once
-    /// EOF is reached for this reader. Otherwise each element yielded will be a
-    /// [`Result`]`<`[`char`]`, E>` where `E` may contain information about what I/O error
-    /// occurred or where decoding failed.
-    ///
-    /// Currently this adaptor will discard intermediate data read, and should
-    /// be avoided if this is not desired.
-    ///
-    /// # Examples
-    ///
-    /// [`File`]s implement `Read`:
-    ///
-    /// [`File`]: ../fs/struct.File.html
-    /// [`Iterator`]: ../../std/iter/trait.Iterator.html
-    /// [`Result`]: ../../std/result/enum.Result.html
-    /// [`char`]: ../../std/primitive.char.html
-    /// [`None`]: ../../std/option/enum.Option.html#variant.None
-    ///
-    /// ```no_run
-    /// #![feature(io)]
-    /// use std::io;
-    /// use std::io::prelude::*;
-    /// use std::fs::File;
-    ///
-    /// fn main() -> io::Result<()> {
-    ///     let mut f = File::open("foo.txt")?;
-    ///
-    ///     for c in f.chars() {
-    ///         println!("{}", c.unwrap());
-    ///     }
-    ///     Ok(())
-    /// }
-    /// ```
-    #[unstable(feature = "io", reason = "the semantics of a partial read/write \
-                                         of where errors happen is currently \
-                                         unclear and may change",
-               issue = "27802")]
-    #[rustc_deprecated(since = "1.27.0", reason = "Use str::from_utf8 instead:
-        https://doc.rust-lang.org/nightly/std/str/struct.Utf8Error.html#examples")]
-    #[allow(deprecated)]
-    fn chars(self) -> Chars<Self> where Self: Sized {
-        Chars { inner: self }
-    }
-
     /// Creates an adaptor which will chain this stream with another.
     ///
     /// The returned `Read` instance will first read all bytes from this object
@@ -2005,104 +1955,6 @@ impl<R: Read> Iterator for Bytes<R> {
     }
 }
 
-/// An iterator over the `char`s of a reader.
-///
-/// This struct is generally created by calling [`chars`][chars] on a reader.
-/// Please see the documentation of `chars()` for more details.
-///
-/// [chars]: trait.Read.html#method.chars
-#[unstable(feature = "io", reason = "awaiting stability of Read::chars",
-           issue = "27802")]
-#[rustc_deprecated(since = "1.27.0", reason = "Use str::from_utf8 instead:
-    https://doc.rust-lang.org/nightly/std/str/struct.Utf8Error.html#examples")]
-#[derive(Debug)]
-#[allow(deprecated)]
-pub struct Chars<R> {
-    inner: R,
-}
-
-/// An enumeration of possible errors that can be generated from the `Chars`
-/// adapter.
-#[unstable(feature = "io", reason = "awaiting stability of Read::chars",
-           issue = "27802")]
-#[rustc_deprecated(since = "1.27.0", reason = "Use str::from_utf8 instead:
-    https://doc.rust-lang.org/nightly/std/str/struct.Utf8Error.html#examples")]
-#[derive(Debug)]
-#[allow(deprecated)]
-pub enum CharsError {
-    /// Variant representing that the underlying stream was read successfully
-    /// but it did not contain valid utf8 data.
-    NotUtf8,
-
-    /// Variant representing that an I/O error occurred.
-    Other(Error),
-}
-
-#[unstable(feature = "io", reason = "awaiting stability of Read::chars",
-           issue = "27802")]
-#[allow(deprecated)]
-impl<R: Read> Iterator for Chars<R> {
-    type Item = result::Result<char, CharsError>;
-
-    fn next(&mut self) -> Option<result::Result<char, CharsError>> {
-        let first_byte = match read_one_byte(&mut self.inner)? {
-            Ok(b) => b,
-            Err(e) => return Some(Err(CharsError::Other(e))),
-        };
-        let width = core_str::utf8_char_width(first_byte);
-        if width == 1 { return Some(Ok(first_byte as char)) }
-        if width == 0 { return Some(Err(CharsError::NotUtf8)) }
-        let mut buf = [first_byte, 0, 0, 0];
-        {
-            let mut start = 1;
-            while start < width {
-                match self.inner.read(&mut buf[start..width]) {
-                    Ok(0) => return Some(Err(CharsError::NotUtf8)),
-                    Ok(n) => start += n,
-                    Err(ref e) if e.kind() == ErrorKind::Interrupted => continue,
-                    Err(e) => return Some(Err(CharsError::Other(e))),
-                }
-            }
-        }
-        Some(match str::from_utf8(&buf[..width]).ok() {
-            Some(s) => Ok(s.chars().next().unwrap()),
-            None => Err(CharsError::NotUtf8),
-        })
-    }
-}
-
-#[unstable(feature = "io", reason = "awaiting stability of Read::chars",
-           issue = "27802")]
-#[allow(deprecated)]
-impl std_error::Error for CharsError {
-    fn description(&self) -> &str {
-        match *self {
-            CharsError::NotUtf8 => "invalid utf8 encoding",
-            CharsError::Other(ref e) => std_error::Error::description(e),
-        }
-    }
-    fn cause(&self) -> Option<&dyn std_error::Error> {
-        match *self {
-            CharsError::NotUtf8 => None,
-            CharsError::Other(ref e) => e.cause(),
-        }
-    }
-}
-
-#[unstable(feature = "io", reason = "awaiting stability of Read::chars",
-           issue = "27802")]
-#[allow(deprecated)]
-impl fmt::Display for CharsError {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        match *self {
-            CharsError::NotUtf8 => {
-                "byte stream did not contain valid utf8".fmt(f)
-            }
-            CharsError::Other(ref e) => e.fmt(f),
-        }
-    }
-}
-
 /// An iterator over the contents of an instance of `BufRead` split on a
 /// particular byte.
 ///