Auto merge of #44042 - LukasKalbertodt:ascii-methods-on-instrinsics, r=alexcrichton

Copy all `AsciiExt` methods to the primitive types directly in order to deprecate it later

**EDIT:** [this PR is ready now](https://github.com/rust-lang/rust/pull/44042#issuecomment-333883548). I edited this post to reflect the current status of discussion, which is (apart from code review) pretty much settled.

---

This is my current progress in order to prepare stabilization of #39658. As discussed there (and in #39659), the idea is to deprecated `AsciiExt` and copy all methods to the type directly. Apparently there isn't really a reason to have those methods in an extension trait¹.

~~This is **work in progress**: copy&pasting code while slightly modifying the documentation isn't the most exciting thing to do. Therefore I wanted to already open this WIP PR after doing basically 1/4 of the job (copying methods to `&[u8]`, `char` and `&str` is still missing) to get some feedback before I continue. Some questions possibly worth discussing:~~

1. ~~Does everyone agree that deprecating `AsciiExt` is a good idea? Does everyone agree with the goal of this PR?~~ => apparently yes
2. ~~Are my changes OK so far? Did I do something wrong?~~
3. ~~The issue of the unstable-attribute is currently set to 0. I would wait until you say "Ok" to the whole thing, then create a tracking issue and then insert the correct issue id. Is that ok?~~
4. ~~I tweaked `eq_ignore_ascii_case()`: it now takes the argument `other: u8` instead of `other: &u8`. The latter was enforced by the trait. Since we're not bound to a trait anymore, we can drop the reference, ok?~~ => I reverted this, because the interface has to match the `AsciiExt` interface exactly.

¹ ~~Could it be that we can't write `impl [u8] {}`? This might be the reason for `AsciiExt`. If that is the case: is there a good reason we can't write such an impl block? What can we do instead?~~ => we couldn't at the time this PR was opened, but Simon made it possible.

/cc @SimonSapin @zackw

28 files changed, 1791 insertions, 625 deletions

diff --git a/src/liballoc/benches/str.rs b/src/liballoc/benches/str.rs
index fc4063fae92..38c94d4d8b5 100644
--- a/src/liballoc/benches/str.rs
+++ b/src/liballoc/benches/str.rs
@@ -272,15 +272,12 @@ make_test!(match_indices_a_str, s, s.match_indices("a").count());
 make_test!(split_a_str, s, s.split("a").count());
 
 make_test!(trim_ascii_char, s, {
-    use std::ascii::AsciiExt;
     s.trim_matches(|c: char| c.is_ascii())
 });
 make_test!(trim_left_ascii_char, s, {
-    use std::ascii::AsciiExt;
     s.trim_left_matches(|c: char| c.is_ascii())
 });
 make_test!(trim_right_ascii_char, s, {
-    use std::ascii::AsciiExt;
     s.trim_right_matches(|c: char| c.is_ascii())
 });
 
diff --git a/src/liballoc/borrow.rs b/src/liballoc/borrow.rs
index a662e4b1f4f..e8aff099871 100644
--- a/src/liballoc/borrow.rs
+++ b/src/liballoc/borrow.rs
@@ -191,7 +191,6 @@ impl<'a, B: ?Sized> Cow<'a, B>
     /// # Examples
     ///
     /// ```
-    /// use std::ascii::AsciiExt;
     /// use std::borrow::Cow;
     ///
     /// let mut cow = Cow::Borrowed("foo");
diff --git a/src/liballoc/lib.rs b/src/liballoc/lib.rs
index f654a6b5ba4..a40ed060604 100644
--- a/src/liballoc/lib.rs
+++ b/src/liballoc/lib.rs
@@ -83,6 +83,7 @@
 #![cfg_attr(not(test), feature(generator_trait))]
 #![cfg_attr(test, feature(rand, test))]
 #![feature(allow_internal_unstable)]
+#![feature(ascii_ctype)]
 #![feature(box_patterns)]
 #![feature(box_syntax)]
 #![feature(cfg_target_has_atomic)]
diff --git a/src/liballoc/slice.rs b/src/liballoc/slice.rs
index 0c5fec2cf74..b41cb912fe7 100644
--- a/src/liballoc/slice.rs
+++ b/src/liballoc/slice.rs
@@ -1533,6 +1533,215 @@ impl<T> [T] {
     }
 }
 
+// FIXME(LukasKalbertodt): the `not(stage0)` constraint can be removed in the
+// future once the stage0 compiler is new enough to know about the `slice_u8`
+// lang item.
+#[lang = "slice_u8"]
+#[cfg(all(not(stage0), not(test)))]
+impl [u8] {
+    /// Checks if all bytes in this slice are within the ASCII range.
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[inline]
+    pub fn is_ascii(&self) -> bool {
+        self.iter().all(|b| b.is_ascii())
+    }
+
+    /// Returns a vector containing a copy of this slice where each byte
+    /// is mapped to its ASCII upper case equivalent.
+    ///
+    /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
+    /// but non-ASCII letters are unchanged.
+    ///
+    /// To uppercase the value in-place, use [`make_ascii_uppercase`].
+    ///
+    /// [`make_ascii_uppercase`]: #method.make_ascii_uppercase
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[inline]
+    pub fn to_ascii_uppercase(&self) -> Vec<u8> {
+        let mut me = self.to_vec();
+        me.make_ascii_uppercase();
+        me
+    }
+
+    /// Returns a vector containing a copy of this slice where each byte
+    /// is mapped to its ASCII lower case equivalent.
+    ///
+    /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
+    /// but non-ASCII letters are unchanged.
+    ///
+    /// To lowercase the value in-place, use [`make_ascii_lowercase`].
+    ///
+    /// [`make_ascii_lowercase`]: #method.make_ascii_lowercase
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[inline]
+    pub fn to_ascii_lowercase(&self) -> Vec<u8> {
+        let mut me = self.to_vec();
+        me.make_ascii_lowercase();
+        me
+    }
+
+    /// Checks that two slices are an ASCII case-insensitive match.
+    ///
+    /// Same as `to_ascii_lowercase(a) == to_ascii_lowercase(b)`,
+    /// but without allocating and copying temporaries.
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[inline]
+    pub fn eq_ignore_ascii_case(&self, other: &[u8]) -> bool {
+        self.len() == other.len() &&
+            self.iter().zip(other).all(|(a, b)| {
+                a.eq_ignore_ascii_case(b)
+            })
+    }
+
+    /// Converts this slice to its ASCII upper case equivalent in-place.
+    ///
+    /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
+    /// but non-ASCII letters are unchanged.
+    ///
+    /// To return a new uppercased value without modifying the existing one, use
+    /// [`to_ascii_uppercase`].
+    ///
+    /// [`to_ascii_uppercase`]: #method.to_ascii_uppercase
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[inline]
+    pub fn make_ascii_uppercase(&mut self) {
+        for byte in self {
+            byte.make_ascii_uppercase();
+        }
+    }
+
+    /// Converts this slice to its ASCII lower case equivalent in-place.
+    ///
+    /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
+    /// but non-ASCII letters are unchanged.
+    ///
+    /// To return a new lowercased value without modifying the existing one, use
+    /// [`to_ascii_lowercase`].
+    ///
+    /// [`to_ascii_lowercase`]: #method.to_ascii_lowercase
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[inline]
+    pub fn make_ascii_lowercase(&mut self) {
+        for byte in self {
+            byte.make_ascii_lowercase();
+        }
+    }
+
+    /// Checks if all bytes of this slice are ASCII alphabetic characters:
+    ///
+    /// - U+0041 'A' ... U+005A 'Z', or
+    /// - U+0061 'a' ... U+007A 'z'.
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_alphabetic(&self) -> bool {
+        self.iter().all(|b| b.is_ascii_alphabetic())
+    }
+
+    /// Checks if all bytes of this slice are ASCII uppercase characters:
+    /// U+0041 'A' ... U+005A 'Z'.
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_uppercase(&self) -> bool {
+        self.iter().all(|b| b.is_ascii_uppercase())
+    }
+
+    /// Checks if all bytes of this slice are ASCII lowercase characters:
+    /// U+0061 'a' ... U+007A 'z'.
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_lowercase(&self) -> bool {
+        self.iter().all(|b| b.is_ascii_lowercase())
+    }
+
+    /// Checks if all bytes of this slice are ASCII alphanumeric characters:
+    ///
+    /// - U+0041 'A' ... U+005A 'Z', or
+    /// - U+0061 'a' ... U+007A 'z', or
+    /// - U+0030 '0' ... U+0039 '9'.
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_alphanumeric(&self) -> bool {
+        self.iter().all(|b| b.is_ascii_alphanumeric())
+    }
+
+    /// Checks if all bytes of this slice are ASCII decimal digit:
+    /// U+0030 '0' ... U+0039 '9'.
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_digit(&self) -> bool {
+        self.iter().all(|b| b.is_ascii_digit())
+    }
+
+    /// Checks if all bytes of this slice are ASCII hexadecimal digits:
+    ///
+    /// - U+0030 '0' ... U+0039 '9', or
+    /// - U+0041 'A' ... U+0046 'F', or
+    /// - U+0061 'a' ... U+0066 'f'.
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_hexdigit(&self) -> bool {
+        self.iter().all(|b| b.is_ascii_hexdigit())
+    }
+
+    /// Checks if all bytes of this slice are ASCII punctuation characters:
+    ///
+    /// - U+0021 ... U+002F `! " # $ % & ' ( ) * + , - . /`, or
+    /// - U+003A ... U+0040 `: ; < = > ? @`, or
+    /// - U+005B ... U+0060 `[ \\ ] ^ _ \``, or
+    /// - U+007B ... U+007E `{ | } ~`
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_punctuation(&self) -> bool {
+        self.iter().all(|b| b.is_ascii_punctuation())
+    }
+
+    /// Checks if all bytes of this slice are ASCII graphic characters:
+    /// U+0021 '@' ... U+007E '~'.
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_graphic(&self) -> bool {
+        self.iter().all(|b| b.is_ascii_graphic())
+    }
+
+    /// Checks if all bytes of this slice are ASCII whitespace characters:
+    /// U+0020 SPACE, U+0009 HORIZONTAL TAB, U+000A LINE FEED,
+    /// U+000C FORM FEED, or U+000D CARRIAGE RETURN.
+    ///
+    /// 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
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_whitespace(&self) -> bool {
+        self.iter().all(|b| b.is_ascii_whitespace())
+    }
+
+    /// Checks if all bytes of this slice are ASCII control characters:
+    ///
+    /// - U+0000 NUL ... U+001F UNIT SEPARATOR, or
+    /// - U+007F DELETE.
+    ///
+    /// Note that most ASCII whitespace characters are control
+    /// characters, but SPACE is not.
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_control(&self) -> bool {
+        self.iter().all(|b| b.is_ascii_control())
+    }
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // Extension traits for slices over specific kinds of data
 ////////////////////////////////////////////////////////////////////////////////
diff --git a/src/liballoc/str.rs b/src/liballoc/str.rs
index 895607ff8d4..5f0b4088fc0 100644
--- a/src/liballoc/str.rs
+++ b/src/liballoc/str.rs
@@ -390,8 +390,6 @@ impl str {
     /// # Examples
     ///
     /// ```
-    /// use std::ascii::AsciiExt;
-    ///
     /// let mut v = String::from("hello");
     /// // correct length
     /// assert!(v.get_mut(0..5).is_some());
@@ -617,8 +615,6 @@ impl str {
     /// Basic usage:
     ///
     /// ```
-    /// use std::ascii::AsciiExt;
-    ///
     /// let mut s = "Per Martin-Löf".to_string();
     /// {
     ///     let (first, last) = s.split_at_mut(3);
@@ -2070,6 +2066,286 @@ impl str {
         s.extend((0..n).map(|_| self));
         s
     }
+
+    /// Checks if all characters in this string are within the ASCII range.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let ascii = "hello!\n";
+    /// let non_ascii = "Grüße, Jürgen ❤";
+    ///
+    /// assert!(ascii.is_ascii());
+    /// assert!(!non_ascii.is_ascii());
+    /// ```
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[inline]
+    pub fn is_ascii(&self) -> bool {
+        // We can treat each byte as character here: all multibyte characters
+        // start with a byte that is not in the ascii range, so we will stop
+        // there already.
+        self.bytes().all(|b| b.is_ascii())
+    }
+
+    /// Returns a copy of this string where each character is mapped to its
+    /// ASCII upper case equivalent.
+    ///
+    /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
+    /// but non-ASCII letters are unchanged.
+    ///
+    /// To uppercase the value in-place, use [`make_ascii_uppercase`].
+    ///
+    /// To uppercase ASCII characters in addition to non-ASCII characters, use
+    /// [`to_uppercase`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let s = "Grüße, Jürgen ❤";
+    ///
+    /// assert_eq!("GRüßE, JüRGEN ❤", s.to_ascii_uppercase());
+    /// ```
+    ///
+    /// [`make_ascii_uppercase`]: #method.make_ascii_uppercase
+    /// [`to_uppercase`]: #method.to_uppercase
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[inline]
+    #[cfg(not(stage0))]
+    pub fn to_ascii_uppercase(&self) -> String {
+        let mut bytes = self.as_bytes().to_vec();
+        bytes.make_ascii_uppercase();
+        // make_ascii_uppercase() preserves the UTF-8 invariant.
+        unsafe { String::from_utf8_unchecked(bytes) }
+    }
+
+    /// Returns a copy of this string where each character is mapped to its
+    /// ASCII lower case equivalent.
+    ///
+    /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
+    /// but non-ASCII letters are unchanged.
+    ///
+    /// To lowercase the value in-place, use [`make_ascii_lowercase`].
+    ///
+    /// To lowercase ASCII characters in addition to non-ASCII characters, use
+    /// [`to_lowercase`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let s = "Grüße, Jürgen ❤";
+    ///
+    /// assert_eq!("grüße, jürgen ❤", s.to_ascii_lowercase());
+    /// ```
+    ///
+    /// [`make_ascii_lowercase`]: #method.make_ascii_lowercase
+    /// [`to_lowercase`]: #method.to_lowercase
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[inline]
+    #[cfg(not(stage0))]
+    pub fn to_ascii_lowercase(&self) -> String {
+        let mut bytes = self.as_bytes().to_vec();
+        bytes.make_ascii_lowercase();
+        // make_ascii_lowercase() preserves the UTF-8 invariant.
+        unsafe { String::from_utf8_unchecked(bytes) }
+    }
+
+    /// Checks that two strings are an ASCII case-insensitive match.
+    ///
+    /// Same as `to_ascii_lowercase(a) == to_ascii_lowercase(b)`,
+    /// but without allocating and copying temporaries.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// assert!("Ferris".eq_ignore_ascii_case("FERRIS"));
+    /// assert!("Ferrös".eq_ignore_ascii_case("FERRöS"));
+    /// assert!(!"Ferrös".eq_ignore_ascii_case("FERRÖS"));
+    /// ```
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[inline]
+    #[cfg(not(stage0))]
+    pub fn eq_ignore_ascii_case(&self, other: &str) -> bool {
+        self.as_bytes().eq_ignore_ascii_case(other.as_bytes())
+    }
+
+    /// Converts this string to its ASCII upper case equivalent in-place.
+    ///
+    /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
+    /// but non-ASCII letters are unchanged.
+    ///
+    /// To return a new uppercased value without modifying the existing one, use
+    /// [`to_ascii_uppercase`].
+    ///
+    /// [`to_ascii_uppercase`]: #method.to_ascii_uppercase
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[cfg(not(stage0))]
+    pub fn make_ascii_uppercase(&mut self) {
+        let me = unsafe { self.as_bytes_mut() };
+        me.make_ascii_uppercase()
+    }
+
+    /// Converts this string to its ASCII lower case equivalent in-place.
+    ///
+    /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
+    /// but non-ASCII letters are unchanged.
+    ///
+    /// To return a new lowercased value without modifying the existing one, use
+    /// [`to_ascii_lowercase`].
+    ///
+    /// [`to_ascii_lowercase`]: #method.to_ascii_lowercase
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[cfg(not(stage0))]
+    pub fn make_ascii_lowercase(&mut self) {
+        let me = unsafe { self.as_bytes_mut() };
+        me.make_ascii_lowercase()
+    }
+
+    /// Checks if all characters of this string are ASCII alphabetic
+    /// characters:
+    ///
+    /// - U+0041 'A' ... U+005A 'Z', or
+    /// - U+0061 'a' ... U+007A 'z'.
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_alphabetic(&self) -> bool {
+        self.bytes().all(|b| b.is_ascii_alphabetic())
+    }
+
+    /// Checks if all characters of this string are ASCII uppercase characters:
+    /// U+0041 'A' ... U+005A 'Z'.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// #![feature(ascii_ctype)]
+    ///
+    /// // Only ascii uppercase characters
+    /// assert!("HELLO".is_ascii_uppercase());
+    ///
+    /// // While all characters are ascii, 'y' and 'e' are not uppercase
+    /// assert!(!"Bye".is_ascii_uppercase());
+    ///
+    /// // While all characters are uppercase, 'Ü' is not ascii
+    /// assert!(!"TSCHÜSS".is_ascii_uppercase());
+    /// ```
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_uppercase(&self) -> bool {
+        self.bytes().all(|b| b.is_ascii_uppercase())
+    }
+
+    /// Checks if all characters of this string are ASCII lowercase characters:
+    /// U+0061 'a' ... U+007A 'z'.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// #![feature(ascii_ctype)]
+    ///
+    /// // Only ascii uppercase characters
+    /// assert!("hello".is_ascii_lowercase());
+    ///
+    /// // While all characters are ascii, 'B' is not lowercase
+    /// assert!(!"Bye".is_ascii_lowercase());
+    ///
+    /// // While all characters are lowercase, 'Ü' is not ascii
+    /// assert!(!"tschüss".is_ascii_lowercase());
+    /// ```
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_lowercase(&self) -> bool {
+        self.bytes().all(|b| b.is_ascii_lowercase())
+    }
+
+    /// Checks if all characters of this string are ASCII alphanumeric
+    /// characters:
+    ///
+    /// - U+0041 'A' ... U+005A 'Z', or
+    /// - U+0061 'a' ... U+007A 'z', or
+    /// - U+0030 '0' ... U+0039 '9'.
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_alphanumeric(&self) -> bool {
+        self.bytes().all(|b| b.is_ascii_alphanumeric())
+    }
+
+    /// Checks if all characters of this string are ASCII decimal digit:
+    /// U+0030 '0' ... U+0039 '9'.
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_digit(&self) -> bool {
+        self.bytes().all(|b| b.is_ascii_digit())
+    }
+
+    /// Checks if all characters of this string are ASCII hexadecimal digits:
+    ///
+    /// - U+0030 '0' ... U+0039 '9', or
+    /// - U+0041 'A' ... U+0046 'F', or
+    /// - U+0061 'a' ... U+0066 'f'.
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_hexdigit(&self) -> bool {
+        self.bytes().all(|b| b.is_ascii_hexdigit())
+    }
+
+    /// Checks if all characters of this string are ASCII punctuation
+    /// characters:
+    ///
+    /// - U+0021 ... U+002F `! " # $ % & ' ( ) * + , - . /`, or
+    /// - U+003A ... U+0040 `: ; < = > ? @`, or
+    /// - U+005B ... U+0060 `[ \\ ] ^ _ \``, or
+    /// - U+007B ... U+007E `{ | } ~`
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_punctuation(&self) -> bool {
+        self.bytes().all(|b| b.is_ascii_punctuation())
+    }
+
+    /// Checks if all characters of this string are ASCII graphic characters:
+    /// U+0021 '@' ... U+007E '~'.
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_graphic(&self) -> bool {
+        self.bytes().all(|b| b.is_ascii_graphic())
+    }
+
+    /// Checks if all characters of this string are ASCII whitespace characters:
+    /// U+0020 SPACE, U+0009 HORIZONTAL TAB, U+000A LINE FEED,
+    /// U+000C FORM FEED, or U+000D CARRIAGE RETURN.
+    ///
+    /// 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
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_whitespace(&self) -> bool {
+        self.bytes().all(|b| b.is_ascii_whitespace())
+    }
+
+    /// Checks if all characters of this string are ASCII control characters:
+    ///
+    /// - U+0000 NUL ... U+001F UNIT SEPARATOR, or
+    /// - U+007F DELETE.
+    ///
+    /// Note that most ASCII whitespace characters are control
+    /// characters, but SPACE is not.
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_control(&self) -> bool {
+        self.bytes().all(|b| b.is_ascii_control())
+    }
 }
 
 /// Converts a boxed slice of bytes to a boxed string slice without checking
diff --git a/src/liballoc/string.rs b/src/liballoc/string.rs
index 6d0bb264df1..25fcc1ccdab 100644
--- a/src/liballoc/string.rs
+++ b/src/liballoc/string.rs
@@ -773,8 +773,6 @@ impl String {
     /// Basic usage:
     ///
     /// ```
-    /// use std::ascii::AsciiExt;
-    ///
     /// let mut s = String::from("foobar");
     /// let s_mut_str = s.as_mut_str();
     ///
diff --git a/src/liballoc/tests/str.rs b/src/liballoc/tests/str.rs
index b3178064505..6b075e7ac0e 100644
--- a/src/liballoc/tests/str.rs
+++ b/src/liballoc/tests/str.rs
@@ -706,7 +706,6 @@ fn test_split_at() {
 
 #[test]
 fn test_split_at_mut() {
-    use std::ascii::AsciiExt;
     let mut s = "Hello World".to_string();
     {
         let (a, b) = s.split_at_mut(5);
diff --git a/src/liballoc/tests/vec.rs b/src/liballoc/tests/vec.rs
index 0e25da5bd30..9cfde5dcc73 100644
--- a/src/liballoc/tests/vec.rs
+++ b/src/liballoc/tests/vec.rs
@@ -8,7 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use std::ascii::AsciiExt;
 use std::borrow::Cow;
 use std::mem::size_of;
 use std::panic;
@@ -966,5 +965,3 @@ fn drain_filter_complex() {
         assert_eq!(vec, vec![1, 3, 5, 7, 9, 11, 13, 15, 17, 19]);
     }
 }
-
-
diff --git a/src/liballoc/vec.rs b/src/liballoc/vec.rs
index cf34e195dea..5aca199cf40 100644
--- a/src/liballoc/vec.rs
+++ b/src/liballoc/vec.rs
@@ -853,8 +853,6 @@ impl<T> Vec<T> {
     /// # Examples
     ///
     /// ```
-    /// use std::ascii::AsciiExt;
-    ///
     /// let mut vec = vec!["foo", "bar", "Bar", "baz", "bar"];
     ///
     /// vec.dedup_by(|a, b| a.eq_ignore_ascii_case(b));
diff --git a/src/libcore/num/mod.rs b/src/libcore/num/mod.rs
index a50779bedfd..7fe0aabeec9 100644
--- a/src/libcore/num/mod.rs
+++ b/src/libcore/num/mod.rs
@@ -2259,6 +2259,547 @@ impl u8 {
         intrinsics::add_with_overflow,
         intrinsics::sub_with_overflow,
         intrinsics::mul_with_overflow }
+
+
+    /// Checks if the value is within the ASCII range.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let ascii = 97u8;
+    /// let non_ascii = 150u8;
+    ///
+    /// assert!(ascii.is_ascii());
+    /// assert!(!non_ascii.is_ascii());
+    /// ```
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[inline]
+    pub fn is_ascii(&self) -> bool {
+        *self & 128 == 0
+    }
+
+    /// Makes a copy of the value in its ASCII upper case equivalent.
+    ///
+    /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
+    /// but non-ASCII letters are unchanged.
+    ///
+    /// To uppercase the value in-place, use [`make_ascii_uppercase`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let lowercase_a = 97u8;
+    ///
+    /// assert_eq!(65, lowercase_a.to_ascii_uppercase());
+    /// ```
+    ///
+    /// [`make_ascii_uppercase`]: #method.make_ascii_uppercase
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[inline]
+    pub fn to_ascii_uppercase(&self) -> u8 {
+        ASCII_UPPERCASE_MAP[*self as usize]
+    }
+
+    /// Makes a copy of the value in its ASCII lower case equivalent.
+    ///
+    /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
+    /// but non-ASCII letters are unchanged.
+    ///
+    /// To lowercase the value in-place, use [`make_ascii_lowercase`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let uppercase_a = 65u8;
+    ///
+    /// assert_eq!(97, uppercase_a.to_ascii_lowercase());
+    /// ```
+    ///
+    /// [`make_ascii_lowercase`]: #method.make_ascii_lowercase
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[inline]
+    pub fn to_ascii_lowercase(&self) -> u8 {
+        ASCII_LOWERCASE_MAP[*self as usize]
+    }
+
+    /// Checks that two values are an ASCII case-insensitive match.
+    ///
+    /// This is equivalent to `to_ascii_lowercase(a) == to_ascii_lowercase(b)`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let lowercase_a = 97u8;
+    /// let uppercase_a = 65u8;
+    ///
+    /// assert!(lowercase_a.eq_ignore_ascii_case(&uppercase_a));
+    /// ```
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[inline]
+    pub fn eq_ignore_ascii_case(&self, other: &u8) -> bool {
+        self.to_ascii_lowercase() == other.to_ascii_lowercase()
+    }
+
+    /// Converts this value to its ASCII upper case equivalent in-place.
+    ///
+    /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
+    /// but non-ASCII letters are unchanged.
+    ///
+    /// To return a new uppercased value without modifying the existing one, use
+    /// [`to_ascii_uppercase`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let mut byte = b'a';
+    ///
+    /// byte.make_ascii_uppercase();
+    ///
+    /// assert_eq!(b'A', byte);
+    /// ```
+    ///
+    /// [`to_ascii_uppercase`]: #method.to_ascii_uppercase
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[inline]
+    pub fn make_ascii_uppercase(&mut self) {
+        *self = self.to_ascii_uppercase();
+    }
+
+    /// Converts this value to its ASCII lower case equivalent in-place.
+    ///
+    /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
+    /// but non-ASCII letters are unchanged.
+    ///
+    /// To return a new lowercased value without modifying the existing one, use
+    /// [`to_ascii_lowercase`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let mut byte = b'A';
+    ///
+    /// byte.make_ascii_lowercase();
+    ///
+    /// assert_eq!(b'a', byte);
+    /// ```
+    ///
+    /// [`to_ascii_lowercase`]: #method.to_ascii_lowercase
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[inline]
+    pub fn make_ascii_lowercase(&mut self) {
+        *self = self.to_ascii_lowercase();
+    }
+
+    /// Checks if the value is an ASCII alphabetic character:
+    ///
+    /// - U+0041 'A' ... U+005A 'Z', or
+    /// - U+0061 'a' ... U+007A 'z'.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(ascii_ctype)]
+    ///
+    /// let uppercase_a = b'A';
+    /// let uppercase_g = b'G';
+    /// let a = b'a';
+    /// let g = b'g';
+    /// let zero = b'0';
+    /// let percent = b'%';
+    /// let space = b' ';
+    /// let lf = b'\n';
+    /// let esc = 0x1b_u8;
+    ///
+    /// assert!(uppercase_a.is_ascii_alphabetic());
+    /// assert!(uppercase_g.is_ascii_alphabetic());
+    /// assert!(a.is_ascii_alphabetic());
+    /// assert!(g.is_ascii_alphabetic());
+    /// assert!(!zero.is_ascii_alphabetic());
+    /// assert!(!percent.is_ascii_alphabetic());
+    /// assert!(!space.is_ascii_alphabetic());
+    /// assert!(!lf.is_ascii_alphabetic());
+    /// assert!(!esc.is_ascii_alphabetic());
+    /// ```
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_alphabetic(&self) -> bool {
+        if *self >= 0x80 { return false; }
+        match ASCII_CHARACTER_CLASS[*self as usize] {
+            L | Lx | U | Ux => true,
+            _ => false
+        }
+    }
+
+    /// Checks if the value is an ASCII uppercase character:
+    /// U+0041 'A' ... U+005A 'Z'.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(ascii_ctype)]
+    ///
+    /// let uppercase_a = b'A';
+    /// let uppercase_g = b'G';
+    /// let a = b'a';
+    /// let g = b'g';
+    /// let zero = b'0';
+    /// let percent = b'%';
+    /// let space = b' ';
+    /// let lf = b'\n';
+    /// let esc = 0x1b_u8;
+    ///
+    /// assert!(uppercase_a.is_ascii_uppercase());
+    /// assert!(uppercase_g.is_ascii_uppercase());
+    /// assert!(!a.is_ascii_uppercase());
+    /// assert!(!g.is_ascii_uppercase());
+    /// assert!(!zero.is_ascii_uppercase());
+    /// assert!(!percent.is_ascii_uppercase());
+    /// assert!(!space.is_ascii_uppercase());
+    /// assert!(!lf.is_ascii_uppercase());
+    /// assert!(!esc.is_ascii_uppercase());
+    /// ```
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_uppercase(&self) -> bool {
+        if *self >= 0x80 { return false }
+        match ASCII_CHARACTER_CLASS[*self as usize] {
+            U | Ux => true,
+            _ => false
+        }
+    }
+
+    /// Checks if the value is an ASCII lowercase character:
+    /// U+0061 'a' ... U+007A 'z'.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(ascii_ctype)]
+    ///
+    /// let uppercase_a = b'A';
+    /// let uppercase_g = b'G';
+    /// let a = b'a';
+    /// let g = b'g';
+    /// let zero = b'0';
+    /// let percent = b'%';
+    /// let space = b' ';
+    /// let lf = b'\n';
+    /// let esc = 0x1b_u8;
+    ///
+    /// assert!(!uppercase_a.is_ascii_lowercase());
+    /// assert!(!uppercase_g.is_ascii_lowercase());
+    /// assert!(a.is_ascii_lowercase());
+    /// assert!(g.is_ascii_lowercase());
+    /// assert!(!zero.is_ascii_lowercase());
+    /// assert!(!percent.is_ascii_lowercase());
+    /// assert!(!space.is_ascii_lowercase());
+    /// assert!(!lf.is_ascii_lowercase());
+    /// assert!(!esc.is_ascii_lowercase());
+    /// ```
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_lowercase(&self) -> bool {
+        if *self >= 0x80 { return false }
+        match ASCII_CHARACTER_CLASS[*self as usize] {
+            L | Lx => true,
+            _ => false
+        }
+    }
+
+    /// Checks if the value is an ASCII alphanumeric character:
+    ///
+    /// - U+0041 'A' ... U+005A 'Z', or
+    /// - U+0061 'a' ... U+007A 'z', or
+    /// - U+0030 '0' ... U+0039 '9'.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(ascii_ctype)]
+    ///
+    /// let uppercase_a = b'A';
+    /// let uppercase_g = b'G';
+    /// let a = b'a';
+    /// let g = b'g';
+    /// let zero = b'0';
+    /// let percent = b'%';
+    /// let space = b' ';
+    /// let lf = b'\n';
+    /// let esc = 0x1b_u8;
+    ///
+    /// assert!(uppercase_a.is_ascii_alphanumeric());
+    /// assert!(uppercase_g.is_ascii_alphanumeric());
+    /// assert!(a.is_ascii_alphanumeric());
+    /// assert!(g.is_ascii_alphanumeric());
+    /// assert!(zero.is_ascii_alphanumeric());
+    /// assert!(!percent.is_ascii_alphanumeric());
+    /// assert!(!space.is_ascii_alphanumeric());
+    /// assert!(!lf.is_ascii_alphanumeric());
+    /// assert!(!esc.is_ascii_alphanumeric());
+    /// ```
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_alphanumeric(&self) -> bool {
+        if *self >= 0x80 { return false }
+        match ASCII_CHARACTER_CLASS[*self as usize] {
+            D | L | Lx | U | Ux => true,
+            _ => false
+        }
+    }
+
+    /// Checks if the value is an ASCII decimal digit:
+    /// U+0030 '0' ... U+0039 '9'.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(ascii_ctype)]
+    ///
+    /// let uppercase_a = b'A';
+    /// let uppercase_g = b'G';
+    /// let a = b'a';
+    /// let g = b'g';
+    /// let zero = b'0';
+    /// let percent = b'%';
+    /// let space = b' ';
+    /// let lf = b'\n';
+    /// let esc = 0x1b_u8;
+    ///
+    /// assert!(!uppercase_a.is_ascii_digit());
+    /// assert!(!uppercase_g.is_ascii_digit());
+    /// assert!(!a.is_ascii_digit());
+    /// assert!(!g.is_ascii_digit());
+    /// assert!(zero.is_ascii_digit());
+    /// assert!(!percent.is_ascii_digit());
+    /// assert!(!space.is_ascii_digit());
+    /// assert!(!lf.is_ascii_digit());
+    /// assert!(!esc.is_ascii_digit());
+    /// ```
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_digit(&self) -> bool {
+        if *self >= 0x80 { return false }
+        match ASCII_CHARACTER_CLASS[*self as usize] {
+            D => true,
+            _ => false
+        }
+    }
+
+    /// Checks if the value is an ASCII hexadecimal digit:
+    ///
+    /// - U+0030 '0' ... U+0039 '9', or
+    /// - U+0041 'A' ... U+0046 'F', or
+    /// - U+0061 'a' ... U+0066 'f'.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(ascii_ctype)]
+    ///
+    /// let uppercase_a = b'A';
+    /// let uppercase_g = b'G';
+    /// let a = b'a';
+    /// let g = b'g';
+    /// let zero = b'0';
+    /// let percent = b'%';
+    /// let space = b' ';
+    /// let lf = b'\n';
+    /// let esc = 0x1b_u8;
+    ///
+    /// assert!(uppercase_a.is_ascii_hexdigit());
+    /// assert!(!uppercase_g.is_ascii_hexdigit());
+    /// assert!(a.is_ascii_hexdigit());
+    /// assert!(!g.is_ascii_hexdigit());
+    /// assert!(zero.is_ascii_hexdigit());
+    /// assert!(!percent.is_ascii_hexdigit());
+    /// assert!(!space.is_ascii_hexdigit());
+    /// assert!(!lf.is_ascii_hexdigit());
+    /// assert!(!esc.is_ascii_hexdigit());
+    /// ```
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_hexdigit(&self) -> bool {
+        if *self >= 0x80 { return false }
+        match ASCII_CHARACTER_CLASS[*self as usize] {
+            D | Lx | Ux => true,
+            _ => false
+        }
+    }
+
+    /// Checks if the value is an ASCII punctuation character:
+    ///
+    /// - U+0021 ... U+002F `! " # $ % & ' ( ) * + , - . /`, or
+    /// - U+003A ... U+0040 `: ; < = > ? @`, or
+    /// - U+005B ... U+0060 `[ \\ ] ^ _ \``, or
+    /// - U+007B ... U+007E `{ | } ~`
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(ascii_ctype)]
+    ///
+    /// let uppercase_a = b'A';
+    /// let uppercase_g = b'G';
+    /// let a = b'a';
+    /// let g = b'g';
+    /// let zero = b'0';
+    /// let percent = b'%';
+    /// let space = b' ';
+    /// let lf = b'\n';
+    /// let esc = 0x1b_u8;
+    ///
+    /// assert!(!uppercase_a.is_ascii_punctuation());
+    /// assert!(!uppercase_g.is_ascii_punctuation());
+    /// assert!(!a.is_ascii_punctuation());
+    /// assert!(!g.is_ascii_punctuation());
+    /// assert!(!zero.is_ascii_punctuation());
+    /// assert!(percent.is_ascii_punctuation());
+    /// assert!(!space.is_ascii_punctuation());
+    /// assert!(!lf.is_ascii_punctuation());
+    /// assert!(!esc.is_ascii_punctuation());
+    /// ```
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_punctuation(&self) -> bool {
+        if *self >= 0x80 { return false }
+        match ASCII_CHARACTER_CLASS[*self as usize] {
+            P => true,
+            _ => false
+        }
+    }
+
+    /// Checks if the value is an ASCII graphic character:
+    /// U+0021 '@' ... U+007E '~'.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(ascii_ctype)]
+    ///
+    /// let uppercase_a = b'A';
+    /// let uppercase_g = b'G';
+    /// let a = b'a';
+    /// let g = b'g';
+    /// let zero = b'0';
+    /// let percent = b'%';
+    /// let space = b' ';
+    /// let lf = b'\n';
+    /// let esc = 0x1b_u8;
+    ///
+    /// assert!(uppercase_a.is_ascii_graphic());
+    /// assert!(uppercase_g.is_ascii_graphic());
+    /// assert!(a.is_ascii_graphic());
+    /// assert!(g.is_ascii_graphic());
+    /// assert!(zero.is_ascii_graphic());
+    /// assert!(percent.is_ascii_graphic());
+    /// assert!(!space.is_ascii_graphic());
+    /// assert!(!lf.is_ascii_graphic());
+    /// assert!(!esc.is_ascii_graphic());
+    /// ```
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_graphic(&self) -> bool {
+        if *self >= 0x80 { return false; }
+        match ASCII_CHARACTER_CLASS[*self as usize] {
+            Ux | U | Lx | L | D | P => true,
+            _ => false
+        }
+    }
+
+    /// 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.
+    ///
+    /// 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
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(ascii_ctype)]
+    ///
+    /// let uppercase_a = b'A';
+    /// let uppercase_g = b'G';
+    /// let a = b'a';
+    /// let g = b'g';
+    /// let zero = b'0';
+    /// let percent = b'%';
+    /// let space = b' ';
+    /// let lf = b'\n';
+    /// let esc = 0x1b_u8;
+    ///
+    /// assert!(!uppercase_a.is_ascii_whitespace());
+    /// assert!(!uppercase_g.is_ascii_whitespace());
+    /// assert!(!a.is_ascii_whitespace());
+    /// assert!(!g.is_ascii_whitespace());
+    /// assert!(!zero.is_ascii_whitespace());
+    /// assert!(!percent.is_ascii_whitespace());
+    /// assert!(space.is_ascii_whitespace());
+    /// assert!(lf.is_ascii_whitespace());
+    /// assert!(!esc.is_ascii_whitespace());
+    /// ```
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_whitespace(&self) -> bool {
+        if *self >= 0x80 { return false; }
+        match ASCII_CHARACTER_CLASS[*self as usize] {
+            Cw | W => true,
+            _ => false
+        }
+    }
+
+    /// 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.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(ascii_ctype)]
+    ///
+    /// let uppercase_a = b'A';
+    /// let uppercase_g = b'G';
+    /// let a = b'a';
+    /// let g = b'g';
+    /// let zero = b'0';
+    /// let percent = b'%';
+    /// let space = b' ';
+    /// let lf = b'\n';
+    /// let esc = 0x1b_u8;
+    ///
+    /// assert!(!uppercase_a.is_ascii_control());
+    /// assert!(!uppercase_g.is_ascii_control());
+    /// assert!(!a.is_ascii_control());
+    /// assert!(!g.is_ascii_control());
+    /// assert!(!zero.is_ascii_control());
+    /// assert!(!percent.is_ascii_control());
+    /// assert!(!space.is_ascii_control());
+    /// assert!(lf.is_ascii_control());
+    /// assert!(esc.is_ascii_control());
+    /// ```
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_control(&self) -> bool {
+        if *self >= 0x80 { return false; }
+        match ASCII_CHARACTER_CLASS[*self as usize] {
+            C | Cw => true,
+            _ => false
+        }
+    }
 }
 
 #[lang = "u16"]
@@ -2928,3 +3469,106 @@ impl_from! { u32, f64, #[stable(feature = "lossless_float_conv", since = "1.6.0"
 
 // Float -> Float
 impl_from! { f32, f64, #[stable(feature = "lossless_float_conv", since = "1.6.0")] }
+
+static ASCII_LOWERCASE_MAP: [u8; 256] = [
+    0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+    0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
+    0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
+    0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f,
+    b' ', b'!', b'"', b'#', b'$', b'%', b'&', b'\'',
+    b'(', b')', b'*', b'+', b',', b'-', b'.', b'/',
+    b'0', b'1', b'2', b'3', b'4', b'5', b'6', b'7',
+    b'8', b'9', b':', b';', b'<', b'=', b'>', b'?',
+    b'@',
+
+          b'a', b'b', b'c', b'd', b'e', b'f', b'g',
+    b'h', b'i', b'j', b'k', b'l', b'm', b'n', b'o',
+    b'p', b'q', b'r', b's', b't', b'u', b'v', b'w',
+    b'x', b'y', b'z',
+
+                      b'[', b'\\', b']', b'^', b'_',
+    b'`', b'a', b'b', b'c', b'd', b'e', b'f', b'g',
+    b'h', b'i', b'j', b'k', b'l', b'm', b'n', b'o',
+    b'p', b'q', b'r', b's', b't', b'u', b'v', b'w',
+    b'x', b'y', b'z', b'{', b'|', b'}', b'~', 0x7f,
+    0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
+    0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f,
+    0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97,
+    0x98, 0x99, 0x9a, 0x9b, 0x9c, 0x9d, 0x9e, 0x9f,
+    0xa0, 0xa1, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7,
+    0xa8, 0xa9, 0xaa, 0xab, 0xac, 0xad, 0xae, 0xaf,
+    0xb0, 0xb1, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6, 0xb7,
+    0xb8, 0xb9, 0xba, 0xbb, 0xbc, 0xbd, 0xbe, 0xbf,
+    0xc0, 0xc1, 0xc2, 0xc3, 0xc4, 0xc5, 0xc6, 0xc7,
+    0xc8, 0xc9, 0xca, 0xcb, 0xcc, 0xcd, 0xce, 0xcf,
+    0xd0, 0xd1, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7,
+    0xd8, 0xd9, 0xda, 0xdb, 0xdc, 0xdd, 0xde, 0xdf,
+    0xe0, 0xe1, 0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7,
+    0xe8, 0xe9, 0xea, 0xeb, 0xec, 0xed, 0xee, 0xef,
+    0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7,
+    0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff,
+];
+
+static ASCII_UPPERCASE_MAP: [u8; 256] = [
+    0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+    0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
+    0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
+    0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f,
+    b' ', b'!', b'"', b'#', b'$', b'%', b'&', b'\'',
+    b'(', b')', b'*', b'+', b',', b'-', b'.', b'/',
+    b'0', b'1', b'2', b'3', b'4', b'5', b'6', b'7',
+    b'8', b'9', b':', b';', b'<', b'=', b'>', b'?',
+    b'@', b'A', b'B', b'C', b'D', b'E', b'F', b'G',
+    b'H', b'I', b'J', b'K', b'L', b'M', b'N', b'O',
+    b'P', b'Q', b'R', b'S', b'T', b'U', b'V', b'W',
+    b'X', b'Y', b'Z', b'[', b'\\', b']', b'^', b'_',
+    b'`',
+
+          b'A', b'B', b'C', b'D', b'E', b'F', b'G',
+    b'H', b'I', b'J', b'K', b'L', b'M', b'N', b'O',
+    b'P', b'Q', b'R', b'S', b'T', b'U', b'V', b'W',
+    b'X', b'Y', b'Z',
+
+                      b'{', b'|', b'}', b'~', 0x7f,
+    0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
+    0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f,
+    0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97,
+    0x98, 0x99, 0x9a, 0x9b, 0x9c, 0x9d, 0x9e, 0x9f,
+    0xa0, 0xa1, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7,
+    0xa8, 0xa9, 0xaa, 0xab, 0xac, 0xad, 0xae, 0xaf,
+    0xb0, 0xb1, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6, 0xb7,
+    0xb8, 0xb9, 0xba, 0xbb, 0xbc, 0xbd, 0xbe, 0xbf,
+    0xc0, 0xc1, 0xc2, 0xc3, 0xc4, 0xc5, 0xc6, 0xc7,
+    0xc8, 0xc9, 0xca, 0xcb, 0xcc, 0xcd, 0xce, 0xcf,
+    0xd0, 0xd1, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7,
+    0xd8, 0xd9, 0xda, 0xdb, 0xdc, 0xdd, 0xde, 0xdf,
+    0xe0, 0xe1, 0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7,
+    0xe8, 0xe9, 0xea, 0xeb, 0xec, 0xed, 0xee, 0xef,
+    0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7,
+    0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff,
+];
+
+enum AsciiCharacterClass {
+    C,  // control
+    Cw, // control whitespace
+    W,  // whitespace
+    D,  // digit
+    L,  // lowercase
+    Lx, // lowercase hex digit
+    U,  // uppercase
+    Ux, // uppercase hex digit
+    P,  // punctuation
+}
+use self::AsciiCharacterClass::*;
+
+static ASCII_CHARACTER_CLASS: [AsciiCharacterClass; 128] = [
+//  _0 _1 _2 _3 _4 _5 _6 _7 _8 _9 _a _b _c _d _e _f
+    C, C, C, C, C, C, C, C, C, Cw,Cw,C, Cw,Cw,C, C, // 0_
+    C, C, C, C, C, C, C, C, C, C, C, C, C, C, C, C, // 1_
+    W, P, P, P, P, P, P, P, P, P, P, P, P, P, P, P, // 2_
+    D, D, D, D, D, D, D, D, D, D, P, P, P, P, P, P, // 3_
+    P, Ux,Ux,Ux,Ux,Ux,Ux,U, U, U, U, U, U, U, U, U, // 4_
+    U, U, U, U, U, U, U, U, U, U, U, P, P, P, P, P, // 5_
+    P, Lx,Lx,Lx,Lx,Lx,Lx,L, L, L, L, L, L, L, L, L, // 6_
+    L, L, L, L, L, L, L, L, L, L, L, P, P, P, P, C, // 7_
+];
diff --git a/src/librustc/lint/mod.rs b/src/librustc/lint/mod.rs
index bca4dad220f..d648099d74d 100644
--- a/src/librustc/lint/mod.rs
+++ b/src/librustc/lint/mod.rs
@@ -38,6 +38,7 @@ use hir::def_id::{CrateNum, LOCAL_CRATE};
 use hir::intravisit::{self, FnKind};
 use hir;
 use session::Session;
+#[cfg(stage0)]
 use std::ascii::AsciiExt;
 use std::hash;
 use syntax::ast;
diff --git a/src/librustc/middle/lang_items.rs b/src/librustc/middle/lang_items.rs
index 679c4f17a6c..a38b37ff745 100644
--- a/src/librustc/middle/lang_items.rs
+++ b/src/librustc/middle/lang_items.rs
@@ -211,6 +211,7 @@ language_item_table! {
     CharImplItem,                    "char",                    char_impl;
     StrImplItem,                     "str",                     str_impl;
     SliceImplItem,                   "slice",                   slice_impl;
+    SliceU8ImplItem,                 "slice_u8",                slice_u8_impl;
     ConstPtrImplItem,                "const_ptr",               const_ptr_impl;
     MutPtrImplItem,                  "mut_ptr",                 mut_ptr_impl;
     I8ImplItem,                      "i8",                      i8_impl;
diff --git a/src/librustc_typeck/check/method/probe.rs b/src/librustc_typeck/check/method/probe.rs
index a24f420af80..81e5b2fe00a 100644
--- a/src/librustc_typeck/check/method/probe.rs
+++ b/src/librustc_typeck/check/method/probe.rs
@@ -431,6 +431,9 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
             ty::TySlice(_) => {
                 let lang_def_id = lang_items.slice_impl();
                 self.assemble_inherent_impl_for_primitive(lang_def_id);
+
+                let lang_def_id = lang_items.slice_u8_impl();
+                self.assemble_inherent_impl_for_primitive(lang_def_id);
             }
             ty::TyRawPtr(ty::TypeAndMut { ty: _, mutbl: hir::MutImmutable }) => {
                 let lang_def_id = lang_items.const_ptr_impl();
diff --git a/src/librustc_typeck/coherence/inherent_impls.rs b/src/librustc_typeck/coherence/inherent_impls.rs
index c56a3b91ca3..569b6a2febb 100644
--- a/src/librustc_typeck/coherence/inherent_impls.rs
+++ b/src/librustc_typeck/coherence/inherent_impls.rs
@@ -137,6 +137,13 @@ impl<'a, 'tcx, 'v> ItemLikeVisitor<'v> for InherentCollect<'a, 'tcx> {
                                           "str",
                                           item.span);
             }
+            ty::TySlice(slice_item) if slice_item == self.tcx.types.u8 => {
+                self.check_primitive_impl(def_id,
+                                          lang_items.slice_u8_impl(),
+                                          "slice_u8",
+                                          "[u8]",
+                                          item.span);
+            }
             ty::TySlice(_) => {
                 self.check_primitive_impl(def_id,
                                           lang_items.slice_impl(),
diff --git a/src/librustdoc/clean/cfg.rs b/src/librustdoc/clean/cfg.rs
index e3ce403f3c1..915383d8189 100644
--- a/src/librustdoc/clean/cfg.rs
+++ b/src/librustdoc/clean/cfg.rs
@@ -15,6 +15,7 @@
 use std::mem;
 use std::fmt::{self, Write};
 use std::ops;
+#[cfg(stage0)]
 use std::ascii::AsciiExt;
 
 use syntax::symbol::Symbol;
diff --git a/src/librustdoc/html/markdown.rs b/src/librustdoc/html/markdown.rs
index 001e773098e..c132cf75e40 100644
--- a/src/librustdoc/html/markdown.rs
+++ b/src/librustdoc/html/markdown.rs
@@ -30,7 +30,6 @@
 use libc;
 use std::slice;
 
-use std::ascii::AsciiExt;
 use std::cell::RefCell;
 use std::collections::{HashMap, VecDeque};
 use std::default::Default;
diff --git a/src/librustdoc/html/render.rs b/src/librustdoc/html/render.rs
index 7e1742c6e10..f3a897d2121 100644
--- a/src/librustdoc/html/render.rs
+++ b/src/librustdoc/html/render.rs
@@ -34,6 +34,7 @@
 //! both occur before the crate is rendered.
 pub use self::ExternalLocation::*;
 
+#[cfg(stage0)]
 use std::ascii::AsciiExt;
 use std::cell::RefCell;
 use std::cmp::Ordering;
diff --git a/src/librustdoc/lib.rs b/src/librustdoc/lib.rs
index 20da99a6b13..fcb25f7aef3 100644
--- a/src/librustdoc/lib.rs
+++ b/src/librustdoc/lib.rs
@@ -14,6 +14,7 @@
        html_playground_url = "https://play.rust-lang.org/")]
 #![deny(warnings)]
 
+#![feature(ascii_ctype)]
 #![feature(rustc_private)]
 #![feature(box_patterns)]
 #![feature(box_syntax)]
@@ -23,7 +24,6 @@
 #![feature(test)]
 #![feature(unicode)]
 #![feature(vec_remove_item)]
-#![feature(ascii_ctype)]
 
 extern crate arena;
 extern crate getopts;
diff --git a/src/libstd/ascii.rs b/src/libstd/ascii.rs
index 327deb9b419..96d719c528c 100644
--- a/src/libstd/ascii.rs
+++ b/src/libstd/ascii.rs
@@ -38,8 +38,8 @@ use iter::FusedIterator;
 /// ```
 /// use std::ascii::AsciiExt;
 ///
-/// assert_eq!("café".to_ascii_uppercase(), "CAFÉ");
-/// assert_eq!("café".to_ascii_uppercase(), "CAFé");
+/// assert_eq!(AsciiExt::to_ascii_uppercase("café"), "CAFÉ");
+/// assert_eq!(AsciiExt::to_ascii_uppercase("café"), "CAFé");
 /// ```
 ///
 /// In the first example, the lowercased string is represented `"cafe\u{301}"`
@@ -60,19 +60,10 @@ pub trait AsciiExt {
 
     /// Checks if the value is within the ASCII range.
     ///
-    /// # Examples
+    /// # Note
     ///
-    /// ```
-    /// use std::ascii::AsciiExt;
-    ///
-    /// let ascii = 'a';
-    /// let non_ascii = '❤';
-    /// let int_ascii = 97;
-    ///
-    /// assert!(ascii.is_ascii());
-    /// assert!(!non_ascii.is_ascii());
-    /// assert!(int_ascii.is_ascii());
-    /// ```
+    /// This method will be deprecated in favor of the identically-named
+    /// inherent methods on `u8`, `char`, `[u8]` and `str`.
     #[stable(feature = "rust1", since = "1.0.0")]
     fn is_ascii(&self) -> bool;
 
@@ -86,19 +77,10 @@ pub trait AsciiExt {
     /// To uppercase ASCII characters in addition to non-ASCII characters, use
     /// [`str::to_uppercase`].
     ///
-    /// # Examples
-    ///
-    /// ```
-    /// use std::ascii::AsciiExt;
-    ///
-    /// let ascii = 'a';
-    /// let non_ascii = '❤';
-    /// let int_ascii = 97;
+    /// # Note
     ///
-    /// assert_eq!('A', ascii.to_ascii_uppercase());
-    /// assert_eq!('❤', non_ascii.to_ascii_uppercase());
-    /// assert_eq!(65, int_ascii.to_ascii_uppercase());
-    /// ```
+    /// This method will be deprecated in favor of the identically-named
+    /// inherent methods on `u8`, `char`, `[u8]` and `str`.
     ///
     /// [`make_ascii_uppercase`]: #tymethod.make_ascii_uppercase
     /// [`str::to_uppercase`]: ../primitive.str.html#method.to_uppercase
@@ -115,19 +97,10 @@ pub trait AsciiExt {
     /// To lowercase ASCII characters in addition to non-ASCII characters, use
     /// [`str::to_lowercase`].
     ///
-    /// # Examples
+    /// # Note
     ///
-    /// ```
-    /// use std::ascii::AsciiExt;
-    ///
-    /// let ascii = 'A';
-    /// let non_ascii = '❤';
-    /// let int_ascii = 65;
-    ///
-    /// assert_eq!('a', ascii.to_ascii_lowercase());
-    /// assert_eq!('❤', non_ascii.to_ascii_lowercase());
-    /// assert_eq!(97, int_ascii.to_ascii_lowercase());
-    /// ```
+    /// This method will be deprecated in favor of the identically-named
+    /// inherent methods on `u8`, `char`, `[u8]` and `str`.
     ///
     /// [`make_ascii_lowercase`]: #tymethod.make_ascii_lowercase
     /// [`str::to_lowercase`]: ../primitive.str.html#method.to_lowercase
@@ -139,20 +112,10 @@ pub trait AsciiExt {
     /// Same as `to_ascii_lowercase(a) == to_ascii_lowercase(b)`,
     /// but without allocating and copying temporaries.
     ///
-    /// # Examples
-    ///
-    /// ```
-    /// use std::ascii::AsciiExt;
-    ///
-    /// let ascii1 = 'A';
-    /// let ascii2 = 'a';
-    /// let ascii3 = 'A';
-    /// let ascii4 = 'z';
+    /// # Note
     ///
-    /// assert!(ascii1.eq_ignore_ascii_case(&ascii2));
-    /// assert!(ascii1.eq_ignore_ascii_case(&ascii3));
-    /// assert!(!ascii1.eq_ignore_ascii_case(&ascii4));
-    /// ```
+    /// This method will be deprecated in favor of the identically-named
+    /// inherent methods on `u8`, `char`, `[u8]` and `str`.
     #[stable(feature = "rust1", since = "1.0.0")]
     fn eq_ignore_ascii_case(&self, other: &Self) -> bool;
 
@@ -164,17 +127,10 @@ pub trait AsciiExt {
     /// To return a new uppercased value without modifying the existing one, use
     /// [`to_ascii_uppercase`].
     ///
-    /// # Examples
+    /// # Note
     ///
-    /// ```
-    /// use std::ascii::AsciiExt;
-    ///
-    /// let mut ascii = 'a';
-    ///
-    /// ascii.make_ascii_uppercase();
-    ///
-    /// assert_eq!('A', ascii);
-    /// ```
+    /// This method will be deprecated in favor of the identically-named
+    /// inherent methods on `u8`, `char`, `[u8]` and `str`.
     ///
     /// [`to_ascii_uppercase`]: #tymethod.to_ascii_uppercase
     #[stable(feature = "ascii", since = "1.9.0")]
@@ -188,17 +144,10 @@ pub trait AsciiExt {
     /// To return a new lowercased value without modifying the existing one, use
     /// [`to_ascii_lowercase`].
     ///
-    /// # Examples
-    ///
-    /// ```
-    /// use std::ascii::AsciiExt;
+    /// # Note
     ///
-    /// let mut ascii = 'A';
-    ///
-    /// ascii.make_ascii_lowercase();
-    ///
-    /// assert_eq!('a', ascii);
-    /// ```
+    /// This method will be deprecated in favor of the identically-named
+    /// inherent methods on `u8`, `char`, `[u8]` and `str`.
     ///
     /// [`to_ascii_lowercase`]: #tymethod.to_ascii_lowercase
     #[stable(feature = "ascii", since = "1.9.0")]
@@ -209,32 +158,10 @@ pub trait AsciiExt {
     /// For strings, true if all characters in the string are
     /// ASCII alphabetic.
     ///
-    /// # Examples
+    /// # Note
     ///
-    /// ```
-    /// #![feature(ascii_ctype)]
-    /// # #![allow(non_snake_case)]
-    /// use std::ascii::AsciiExt;
-    /// let A = 'A';
-    /// let G = 'G';
-    /// let a = 'a';
-    /// let g = 'g';
-    /// let zero = '0';
-    /// let percent = '%';
-    /// let space = ' ';
-    /// let lf = '\n';
-    /// let esc = '\u{001b}';
-    ///
-    /// assert!(A.is_ascii_alphabetic());
-    /// assert!(G.is_ascii_alphabetic());
-    /// assert!(a.is_ascii_alphabetic());
-    /// assert!(g.is_ascii_alphabetic());
-    /// assert!(!zero.is_ascii_alphabetic());
-    /// assert!(!percent.is_ascii_alphabetic());
-    /// assert!(!space.is_ascii_alphabetic());
-    /// assert!(!lf.is_ascii_alphabetic());
-    /// assert!(!esc.is_ascii_alphabetic());
-    /// ```
+    /// This method will be deprecated in favor of the identically-named
+    /// inherent methods on `u8`, `char`, `[u8]` and `str`.
     #[unstable(feature = "ascii_ctype", issue = "39658")]
     fn is_ascii_alphabetic(&self) -> bool { unimplemented!(); }
 
@@ -243,32 +170,10 @@ pub trait AsciiExt {
     /// For strings, true if all characters in the string are
     /// ASCII uppercase.
     ///
-    /// # Examples
-    ///
-    /// ```
-    /// #![feature(ascii_ctype)]
-    /// # #![allow(non_snake_case)]
-    /// use std::ascii::AsciiExt;
-    /// let A = 'A';
-    /// let G = 'G';
-    /// let a = 'a';
-    /// let g = 'g';
-    /// let zero = '0';
-    /// let percent = '%';
-    /// let space = ' ';
-    /// let lf = '\n';
-    /// let esc = '\u{001b}';
+    /// # Note
     ///
-    /// assert!(A.is_ascii_uppercase());
-    /// assert!(G.is_ascii_uppercase());
-    /// assert!(!a.is_ascii_uppercase());
-    /// assert!(!g.is_ascii_uppercase());
-    /// assert!(!zero.is_ascii_uppercase());
-    /// assert!(!percent.is_ascii_uppercase());
-    /// assert!(!space.is_ascii_uppercase());
-    /// assert!(!lf.is_ascii_uppercase());
-    /// assert!(!esc.is_ascii_uppercase());
-    /// ```
+    /// This method will be deprecated in favor of the identically-named
+    /// inherent methods on `u8`, `char`, `[u8]` and `str`.
     #[unstable(feature = "ascii_ctype", issue = "39658")]
     fn is_ascii_uppercase(&self) -> bool { unimplemented!(); }
 
@@ -277,32 +182,10 @@ pub trait AsciiExt {
     /// For strings, true if all characters in the string are
     /// ASCII lowercase.
     ///
-    /// # Examples
+    /// # Note
     ///
-    /// ```
-    /// #![feature(ascii_ctype)]
-    /// # #![allow(non_snake_case)]
-    /// use std::ascii::AsciiExt;
-    /// let A = 'A';
-    /// let G = 'G';
-    /// let a = 'a';
-    /// let g = 'g';
-    /// let zero = '0';
-    /// let percent = '%';
-    /// let space = ' ';
-    /// let lf = '\n';
-    /// let esc = '\u{001b}';
-    ///
-    /// assert!(!A.is_ascii_lowercase());
-    /// assert!(!G.is_ascii_lowercase());
-    /// assert!(a.is_ascii_lowercase());
-    /// assert!(g.is_ascii_lowercase());
-    /// assert!(!zero.is_ascii_lowercase());
-    /// assert!(!percent.is_ascii_lowercase());
-    /// assert!(!space.is_ascii_lowercase());
-    /// assert!(!lf.is_ascii_lowercase());
-    /// assert!(!esc.is_ascii_lowercase());
-    /// ```
+    /// This method will be deprecated in favor of the identically-named
+    /// inherent methods on `u8`, `char`, `[u8]` and `str`.
     #[unstable(feature = "ascii_ctype", issue = "39658")]
     fn is_ascii_lowercase(&self) -> bool { unimplemented!(); }
 
@@ -312,32 +195,10 @@ pub trait AsciiExt {
     /// For strings, true if all characters in the string are
     /// ASCII alphanumeric.
     ///
-    /// # Examples
-    ///
-    /// ```
-    /// #![feature(ascii_ctype)]
-    /// # #![allow(non_snake_case)]
-    /// use std::ascii::AsciiExt;
-    /// let A = 'A';
-    /// let G = 'G';
-    /// let a = 'a';
-    /// let g = 'g';
-    /// let zero = '0';
-    /// let percent = '%';
-    /// let space = ' ';
-    /// let lf = '\n';
-    /// let esc = '\u{001b}';
+    /// # Note
     ///
-    /// assert!(A.is_ascii_alphanumeric());
-    /// assert!(G.is_ascii_alphanumeric());
-    /// assert!(a.is_ascii_alphanumeric());
-    /// assert!(g.is_ascii_alphanumeric());
-    /// assert!(zero.is_ascii_alphanumeric());
-    /// assert!(!percent.is_ascii_alphanumeric());
-    /// assert!(!space.is_ascii_alphanumeric());
-    /// assert!(!lf.is_ascii_alphanumeric());
-    /// assert!(!esc.is_ascii_alphanumeric());
-    /// ```
+    /// This method will be deprecated in favor of the identically-named
+    /// inherent methods on `u8`, `char`, `[u8]` and `str`.
     #[unstable(feature = "ascii_ctype", issue = "39658")]
     fn is_ascii_alphanumeric(&self) -> bool { unimplemented!(); }
 
@@ -346,32 +207,10 @@ pub trait AsciiExt {
     /// For strings, true if all characters in the string are
     /// ASCII digits.
     ///
-    /// # Examples
+    /// # Note
     ///
-    /// ```
-    /// #![feature(ascii_ctype)]
-    /// # #![allow(non_snake_case)]
-    /// use std::ascii::AsciiExt;
-    /// let A = 'A';
-    /// let G = 'G';
-    /// let a = 'a';
-    /// let g = 'g';
-    /// let zero = '0';
-    /// let percent = '%';
-    /// let space = ' ';
-    /// let lf = '\n';
-    /// let esc = '\u{001b}';
-    ///
-    /// assert!(!A.is_ascii_digit());
-    /// assert!(!G.is_ascii_digit());
-    /// assert!(!a.is_ascii_digit());
-    /// assert!(!g.is_ascii_digit());
-    /// assert!(zero.is_ascii_digit());
-    /// assert!(!percent.is_ascii_digit());
-    /// assert!(!space.is_ascii_digit());
-    /// assert!(!lf.is_ascii_digit());
-    /// assert!(!esc.is_ascii_digit());
-    /// ```
+    /// This method will be deprecated in favor of the identically-named
+    /// inherent methods on `u8`, `char`, `[u8]` and `str`.
     #[unstable(feature = "ascii_ctype", issue = "39658")]
     fn is_ascii_digit(&self) -> bool { unimplemented!(); }
 
@@ -381,32 +220,10 @@ pub trait AsciiExt {
     /// For strings, true if all characters in the string are
     /// ASCII hex digits.
     ///
-    /// # Examples
-    ///
-    /// ```
-    /// #![feature(ascii_ctype)]
-    /// # #![allow(non_snake_case)]
-    /// use std::ascii::AsciiExt;
-    /// let A = 'A';
-    /// let G = 'G';
-    /// let a = 'a';
-    /// let g = 'g';
-    /// let zero = '0';
-    /// let percent = '%';
-    /// let space = ' ';
-    /// let lf = '\n';
-    /// let esc = '\u{001b}';
+    /// # Note
     ///
-    /// assert!(A.is_ascii_hexdigit());
-    /// assert!(!G.is_ascii_hexdigit());
-    /// assert!(a.is_ascii_hexdigit());
-    /// assert!(!g.is_ascii_hexdigit());
-    /// assert!(zero.is_ascii_hexdigit());
-    /// assert!(!percent.is_ascii_hexdigit());
-    /// assert!(!space.is_ascii_hexdigit());
-    /// assert!(!lf.is_ascii_hexdigit());
-    /// assert!(!esc.is_ascii_hexdigit());
-    /// ```
+    /// This method will be deprecated in favor of the identically-named
+    /// inherent methods on `u8`, `char`, `[u8]` and `str`.
     #[unstable(feature = "ascii_ctype", issue = "39658")]
     fn is_ascii_hexdigit(&self) -> bool { unimplemented!(); }
 
@@ -420,32 +237,10 @@ pub trait AsciiExt {
     /// For strings, true if all characters in the string are
     /// ASCII punctuation.
     ///
-    /// # Examples
+    /// # Note
     ///
-    /// ```
-    /// #![feature(ascii_ctype)]
-    /// # #![allow(non_snake_case)]
-    /// use std::ascii::AsciiExt;
-    /// let A = 'A';
-    /// let G = 'G';
-    /// let a = 'a';
-    /// let g = 'g';
-    /// let zero = '0';
-    /// let percent = '%';
-    /// let space = ' ';
-    /// let lf = '\n';
-    /// let esc = '\u{001b}';
-    ///
-    /// assert!(!A.is_ascii_punctuation());
-    /// assert!(!G.is_ascii_punctuation());
-    /// assert!(!a.is_ascii_punctuation());
-    /// assert!(!g.is_ascii_punctuation());
-    /// assert!(!zero.is_ascii_punctuation());
-    /// assert!(percent.is_ascii_punctuation());
-    /// assert!(!space.is_ascii_punctuation());
-    /// assert!(!lf.is_ascii_punctuation());
-    /// assert!(!esc.is_ascii_punctuation());
-    /// ```
+    /// This method will be deprecated in favor of the identically-named
+    /// inherent methods on `u8`, `char`, `[u8]` and `str`.
     #[unstable(feature = "ascii_ctype", issue = "39658")]
     fn is_ascii_punctuation(&self) -> bool { unimplemented!(); }
 
@@ -454,32 +249,10 @@ pub trait AsciiExt {
     /// For strings, true if all characters in the string are
     /// ASCII punctuation.
     ///
-    /// # Examples
-    ///
-    /// ```
-    /// #![feature(ascii_ctype)]
-    /// # #![allow(non_snake_case)]
-    /// use std::ascii::AsciiExt;
-    /// let A = 'A';
-    /// let G = 'G';
-    /// let a = 'a';
-    /// let g = 'g';
-    /// let zero = '0';
-    /// let percent = '%';
-    /// let space = ' ';
-    /// let lf = '\n';
-    /// let esc = '\u{001b}';
+    /// # Note
     ///
-    /// assert!(A.is_ascii_graphic());
-    /// assert!(G.is_ascii_graphic());
-    /// assert!(a.is_ascii_graphic());
-    /// assert!(g.is_ascii_graphic());
-    /// assert!(zero.is_ascii_graphic());
-    /// assert!(percent.is_ascii_graphic());
-    /// assert!(!space.is_ascii_graphic());
-    /// assert!(!lf.is_ascii_graphic());
-    /// assert!(!esc.is_ascii_graphic());
-    /// ```
+    /// This method will be deprecated in favor of the identically-named
+    /// inherent methods on `u8`, `char`, `[u8]` and `str`.
     #[unstable(feature = "ascii_ctype", issue = "39658")]
     fn is_ascii_graphic(&self) -> bool { unimplemented!(); }
 
@@ -505,32 +278,10 @@ pub trait AsciiExt {
     /// [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
     ///
-    /// # Examples
+    /// # Note
     ///
-    /// ```
-    /// #![feature(ascii_ctype)]
-    /// # #![allow(non_snake_case)]
-    /// use std::ascii::AsciiExt;
-    /// let A = 'A';
-    /// let G = 'G';
-    /// let a = 'a';
-    /// let g = 'g';
-    /// let zero = '0';
-    /// let percent = '%';
-    /// let space = ' ';
-    /// let lf = '\n';
-    /// let esc = '\u{001b}';
-    ///
-    /// assert!(!A.is_ascii_whitespace());
-    /// assert!(!G.is_ascii_whitespace());
-    /// assert!(!a.is_ascii_whitespace());
-    /// assert!(!g.is_ascii_whitespace());
-    /// assert!(!zero.is_ascii_whitespace());
-    /// assert!(!percent.is_ascii_whitespace());
-    /// assert!(space.is_ascii_whitespace());
-    /// assert!(lf.is_ascii_whitespace());
-    /// assert!(!esc.is_ascii_whitespace());
-    /// ```
+    /// This method will be deprecated in favor of the identically-named
+    /// inherent methods on `u8`, `char`, `[u8]` and `str`.
     #[unstable(feature = "ascii_ctype", issue = "39658")]
     fn is_ascii_whitespace(&self) -> bool { unimplemented!(); }
 
@@ -539,36 +290,18 @@ pub trait AsciiExt {
     /// Note that most ASCII whitespace characters are control
     /// characters, but SPACE is not.
     ///
-    /// # Examples
-    ///
-    /// ```
-    /// #![feature(ascii_ctype)]
-    /// # #![allow(non_snake_case)]
-    /// use std::ascii::AsciiExt;
-    /// let A = 'A';
-    /// let G = 'G';
-    /// let a = 'a';
-    /// let g = 'g';
-    /// let zero = '0';
-    /// let percent = '%';
-    /// let space = ' ';
-    /// let lf = '\n';
-    /// let esc = '\u{001b}';
+    /// # Note
     ///
-    /// assert!(!A.is_ascii_control());
-    /// assert!(!G.is_ascii_control());
-    /// assert!(!a.is_ascii_control());
-    /// assert!(!g.is_ascii_control());
-    /// assert!(!zero.is_ascii_control());
-    /// assert!(!percent.is_ascii_control());
-    /// assert!(!space.is_ascii_control());
-    /// assert!(lf.is_ascii_control());
-    /// assert!(esc.is_ascii_control());
-    /// ```
+    /// This method will be deprecated in favor of the identically-named
+    /// inherent methods on `u8`, `char`, `[u8]` and `str`.
     #[unstable(feature = "ascii_ctype", issue = "39658")]
     fn is_ascii_control(&self) -> bool { unimplemented!(); }
 }
 
+// FIXME(LukasKalbertodt): this impl block can be removed in the future. This is
+// possible once the stage0 compiler is new enough to contain the inherent
+// ascii methods for `[str]`. See FIXME comment further down.
+#[cfg(stage0)]
 #[stable(feature = "rust1", since = "1.0.0")]
 impl AsciiExt for str {
     type Owned = String;
@@ -660,6 +393,10 @@ impl AsciiExt for str {
     }
 }
 
+// FIXME(LukasKalbertodt): this impl block can be removed in the future. This is
+// possible once the stage0 compiler is new enough to contain the inherent
+// ascii methods for `[u8]`. See FIXME comment further down.
+#[cfg(stage0)]
 #[stable(feature = "rust1", since = "1.0.0")]
 impl AsciiExt for [u8] {
     type Owned = Vec<u8>;
@@ -753,201 +490,77 @@ impl AsciiExt for [u8] {
     }
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
-impl AsciiExt for u8 {
-    type Owned = u8;
-    #[inline]
-    fn is_ascii(&self) -> bool { *self & 128 == 0 }
-    #[inline]
-    fn to_ascii_uppercase(&self) -> u8 { ASCII_UPPERCASE_MAP[*self as usize] }
-    #[inline]
-    fn to_ascii_lowercase(&self) -> u8 { ASCII_LOWERCASE_MAP[*self as usize] }
-    #[inline]
-    fn eq_ignore_ascii_case(&self, other: &u8) -> bool {
-        self.to_ascii_lowercase() == other.to_ascii_lowercase()
-    }
-    #[inline]
-    fn make_ascii_uppercase(&mut self) { *self = self.to_ascii_uppercase(); }
-    #[inline]
-    fn make_ascii_lowercase(&mut self) { *self = self.to_ascii_lowercase(); }
+macro_rules! impl_by_delegating {
+    ($ty:ty, $owned:ty) => {
+        #[stable(feature = "rust1", since = "1.0.0")]
+        impl AsciiExt for $ty {
+            type Owned = $owned;
 
-    #[inline]
-    fn is_ascii_alphabetic(&self) -> bool {
-        if *self >= 0x80 { return false; }
-        match ASCII_CHARACTER_CLASS[*self as usize] {
-            L|Lx|U|Ux => true,
-            _ => false
-        }
-    }
+            #[inline]
+            fn is_ascii(&self) -> bool { self.is_ascii() }
 
-    #[inline]
-    fn is_ascii_uppercase(&self) -> bool {
-        if *self >= 0x80 { return false }
-        match ASCII_CHARACTER_CLASS[*self as usize] {
-            U|Ux => true,
-            _ => false
-        }
-    }
+            #[inline]
+            fn to_ascii_uppercase(&self) -> Self::Owned { self.to_ascii_uppercase() }
 
-    #[inline]
-    fn is_ascii_lowercase(&self) -> bool {
-        if *self >= 0x80 { return false }
-        match ASCII_CHARACTER_CLASS[*self as usize] {
-            L|Lx => true,
-            _ => false
-        }
-    }
+            #[inline]
+            fn to_ascii_lowercase(&self) -> Self::Owned { self.to_ascii_lowercase() }
 
-    #[inline]
-    fn is_ascii_alphanumeric(&self) -> bool {
-        if *self >= 0x80 { return false }
-        match ASCII_CHARACTER_CLASS[*self as usize] {
-            D|L|Lx|U|Ux => true,
-            _ => false
-        }
-    }
+            #[inline]
+            fn eq_ignore_ascii_case(&self, o: &Self) -> bool { self.eq_ignore_ascii_case(o) }
 
-    #[inline]
-    fn is_ascii_digit(&self) -> bool {
-        if *self >= 0x80 { return false }
-        match ASCII_CHARACTER_CLASS[*self as usize] {
-            D => true,
-            _ => false
-        }
-    }
+            #[inline]
+            fn make_ascii_uppercase(&mut self) { self.make_ascii_uppercase(); }
 
-    #[inline]
-    fn is_ascii_hexdigit(&self) -> bool {
-        if *self >= 0x80 { return false }
-        match ASCII_CHARACTER_CLASS[*self as usize] {
-            D|Lx|Ux => true,
-            _ => false
-        }
-    }
+            #[inline]
+            fn make_ascii_lowercase(&mut self) { self.make_ascii_lowercase(); }
 
-    #[inline]
-    fn is_ascii_punctuation(&self) -> bool {
-        if *self >= 0x80 { return false }
-        match ASCII_CHARACTER_CLASS[*self as usize] {
-            P => true,
-            _ => false
-        }
-    }
+            #[inline]
+            fn is_ascii_alphabetic(&self) -> bool { self.is_ascii_alphabetic() }
 
-    #[inline]
-    fn is_ascii_graphic(&self) -> bool {
-        if *self >= 0x80 { return false; }
-        match ASCII_CHARACTER_CLASS[*self as usize] {
-            Ux|U|Lx|L|D|P => true,
-            _ => false
-        }
-    }
+            #[inline]
+            fn is_ascii_uppercase(&self) -> bool { self.is_ascii_uppercase() }
 
-    #[inline]
-    fn is_ascii_whitespace(&self) -> bool {
-        if *self >= 0x80 { return false; }
-        match ASCII_CHARACTER_CLASS[*self as usize] {
-            Cw|W => true,
-            _ => false
-        }
-    }
-
-    #[inline]
-    fn is_ascii_control(&self) -> bool {
-        if *self >= 0x80 { return false; }
-        match ASCII_CHARACTER_CLASS[*self as usize] {
-            C|Cw => true,
-            _ => false
-        }
-    }
-}
-
-#[stable(feature = "rust1", since = "1.0.0")]
-impl AsciiExt for char {
-    type Owned = char;
-    #[inline]
-    fn is_ascii(&self) -> bool {
-        *self as u32 <= 0x7F
-    }
+            #[inline]
+            fn is_ascii_lowercase(&self) -> bool { self.is_ascii_lowercase() }
 
-    #[inline]
-    fn to_ascii_uppercase(&self) -> char {
-        if self.is_ascii() {
-            (*self as u8).to_ascii_uppercase() as char
-        } else {
-            *self
-        }
-    }
+            #[inline]
+            fn is_ascii_alphanumeric(&self) -> bool { self.is_ascii_alphanumeric() }
 
-    #[inline]
-    fn to_ascii_lowercase(&self) -> char {
-        if self.is_ascii() {
-            (*self as u8).to_ascii_lowercase() as char
-        } else {
-            *self
-        }
-    }
+            #[inline]
+            fn is_ascii_digit(&self) -> bool { self.is_ascii_digit() }
 
-    #[inline]
-    fn eq_ignore_ascii_case(&self, other: &char) -> bool {
-        self.to_ascii_lowercase() == other.to_ascii_lowercase()
-    }
+            #[inline]
+            fn is_ascii_hexdigit(&self) -> bool { self.is_ascii_hexdigit() }
 
-    #[inline]
-    fn make_ascii_uppercase(&mut self) { *self = self.to_ascii_uppercase(); }
-    #[inline]
-    fn make_ascii_lowercase(&mut self) { *self = self.to_ascii_lowercase(); }
+            #[inline]
+            fn is_ascii_punctuation(&self) -> bool { self.is_ascii_punctuation() }
 
-    #[inline]
-    fn is_ascii_alphabetic(&self) -> bool {
-        (*self as u32 <= 0x7f) && (*self as u8).is_ascii_alphabetic()
-    }
+            #[inline]
+            fn is_ascii_graphic(&self) -> bool { self.is_ascii_graphic() }
 
-    #[inline]
-    fn is_ascii_uppercase(&self) -> bool {
-        (*self as u32 <= 0x7f) && (*self as u8).is_ascii_uppercase()
-    }
+            #[inline]
+            fn is_ascii_whitespace(&self) -> bool { self.is_ascii_whitespace() }
 
-    #[inline]
-    fn is_ascii_lowercase(&self) -> bool {
-        (*self as u32 <= 0x7f) && (*self as u8).is_ascii_lowercase()
-    }
-
-    #[inline]
-    fn is_ascii_alphanumeric(&self) -> bool {
-        (*self as u32 <= 0x7f) && (*self as u8).is_ascii_alphanumeric()
-    }
-
-    #[inline]
-    fn is_ascii_digit(&self) -> bool {
-        (*self as u32 <= 0x7f) && (*self as u8).is_ascii_digit()
-    }
-
-    #[inline]
-    fn is_ascii_hexdigit(&self) -> bool {
-        (*self as u32 <= 0x7f) && (*self as u8).is_ascii_hexdigit()
-    }
-
-    #[inline]
-    fn is_ascii_punctuation(&self) -> bool {
-        (*self as u32 <= 0x7f) && (*self as u8).is_ascii_punctuation()
+            #[inline]
+            fn is_ascii_control(&self) -> bool { self.is_ascii_control() }
+        }
     }
+}
 
-    #[inline]
-    fn is_ascii_graphic(&self) -> bool {
-        (*self as u32 <= 0x7f) && (*self as u8).is_ascii_graphic()
-    }
+impl_by_delegating!(u8, u8);
+impl_by_delegating!(char, char);
 
-    #[inline]
-    fn is_ascii_whitespace(&self) -> bool {
-        (*self as u32 <= 0x7f) && (*self as u8).is_ascii_whitespace()
-    }
+// FIXME(LukasKalbertodt): the macro invocation should replace the impl block
+// for `[u8]` above. But this is not possible until the stage0 compiler is new
+// enough to contain the inherent ascii methods for `[u8]`.
+#[cfg(not(stage0))]
+impl_by_delegating!([u8], Vec<u8>);
 
-    #[inline]
-    fn is_ascii_control(&self) -> bool {
-        (*self as u32 <= 0x7f) && (*self as u8).is_ascii_control()
-    }
-}
+// FIXME(LukasKalbertodt): the macro invocation should replace the impl block
+// for `str` above. But this is not possible until the stage0 compiler is new
+// enough to contain the inherent ascii methods for `str`.
+#[cfg(not(stage0))]
+impl_by_delegating!(str, String);
 
 /// An iterator over the escaped version of a byte.
 ///
@@ -1066,112 +679,11 @@ impl fmt::Debug for EscapeDefault {
 }
 
 
-static ASCII_LOWERCASE_MAP: [u8; 256] = [
-    0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
-    0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
-    0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
-    0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f,
-    b' ', b'!', b'"', b'#', b'$', b'%', b'&', b'\'',
-    b'(', b')', b'*', b'+', b',', b'-', b'.', b'/',
-    b'0', b'1', b'2', b'3', b'4', b'5', b'6', b'7',
-    b'8', b'9', b':', b';', b'<', b'=', b'>', b'?',
-    b'@',
-
-          b'a', b'b', b'c', b'd', b'e', b'f', b'g',
-    b'h', b'i', b'j', b'k', b'l', b'm', b'n', b'o',
-    b'p', b'q', b'r', b's', b't', b'u', b'v', b'w',
-    b'x', b'y', b'z',
-
-                      b'[', b'\\', b']', b'^', b'_',
-    b'`', b'a', b'b', b'c', b'd', b'e', b'f', b'g',
-    b'h', b'i', b'j', b'k', b'l', b'm', b'n', b'o',
-    b'p', b'q', b'r', b's', b't', b'u', b'v', b'w',
-    b'x', b'y', b'z', b'{', b'|', b'}', b'~', 0x7f,
-    0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
-    0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f,
-    0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97,
-    0x98, 0x99, 0x9a, 0x9b, 0x9c, 0x9d, 0x9e, 0x9f,
-    0xa0, 0xa1, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7,
-    0xa8, 0xa9, 0xaa, 0xab, 0xac, 0xad, 0xae, 0xaf,
-    0xb0, 0xb1, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6, 0xb7,
-    0xb8, 0xb9, 0xba, 0xbb, 0xbc, 0xbd, 0xbe, 0xbf,
-    0xc0, 0xc1, 0xc2, 0xc3, 0xc4, 0xc5, 0xc6, 0xc7,
-    0xc8, 0xc9, 0xca, 0xcb, 0xcc, 0xcd, 0xce, 0xcf,
-    0xd0, 0xd1, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7,
-    0xd8, 0xd9, 0xda, 0xdb, 0xdc, 0xdd, 0xde, 0xdf,
-    0xe0, 0xe1, 0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7,
-    0xe8, 0xe9, 0xea, 0xeb, 0xec, 0xed, 0xee, 0xef,
-    0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7,
-    0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff,
-];
-
-static ASCII_UPPERCASE_MAP: [u8; 256] = [
-    0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
-    0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
-    0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
-    0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f,
-    b' ', b'!', b'"', b'#', b'$', b'%', b'&', b'\'',
-    b'(', b')', b'*', b'+', b',', b'-', b'.', b'/',
-    b'0', b'1', b'2', b'3', b'4', b'5', b'6', b'7',
-    b'8', b'9', b':', b';', b'<', b'=', b'>', b'?',
-    b'@', b'A', b'B', b'C', b'D', b'E', b'F', b'G',
-    b'H', b'I', b'J', b'K', b'L', b'M', b'N', b'O',
-    b'P', b'Q', b'R', b'S', b'T', b'U', b'V', b'W',
-    b'X', b'Y', b'Z', b'[', b'\\', b']', b'^', b'_',
-    b'`',
-
-          b'A', b'B', b'C', b'D', b'E', b'F', b'G',
-    b'H', b'I', b'J', b'K', b'L', b'M', b'N', b'O',
-    b'P', b'Q', b'R', b'S', b'T', b'U', b'V', b'W',
-    b'X', b'Y', b'Z',
-
-                      b'{', b'|', b'}', b'~', 0x7f,
-    0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
-    0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f,
-    0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97,
-    0x98, 0x99, 0x9a, 0x9b, 0x9c, 0x9d, 0x9e, 0x9f,
-    0xa0, 0xa1, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7,
-    0xa8, 0xa9, 0xaa, 0xab, 0xac, 0xad, 0xae, 0xaf,
-    0xb0, 0xb1, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6, 0xb7,
-    0xb8, 0xb9, 0xba, 0xbb, 0xbc, 0xbd, 0xbe, 0xbf,
-    0xc0, 0xc1, 0xc2, 0xc3, 0xc4, 0xc5, 0xc6, 0xc7,
-    0xc8, 0xc9, 0xca, 0xcb, 0xcc, 0xcd, 0xce, 0xcf,
-    0xd0, 0xd1, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7,
-    0xd8, 0xd9, 0xda, 0xdb, 0xdc, 0xdd, 0xde, 0xdf,
-    0xe0, 0xe1, 0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7,
-    0xe8, 0xe9, 0xea, 0xeb, 0xec, 0xed, 0xee, 0xef,
-    0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7,
-    0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff,
-];
-
-enum AsciiCharacterClass {
-    C,  // control
-    Cw, // control whitespace
-    W,  // whitespace
-    D,  // digit
-    L,  // lowercase
-    Lx, // lowercase hex digit
-    U,  // uppercase
-    Ux, // uppercase hex digit
-    P,  // punctuation
-}
-use self::AsciiCharacterClass::*;
-
-static ASCII_CHARACTER_CLASS: [AsciiCharacterClass; 128] = [
-//  _0 _1 _2 _3 _4 _5 _6 _7 _8 _9 _a _b _c _d _e _f
-    C, C, C, C, C, C, C, C, C, Cw,Cw,C, Cw,Cw,C, C, // 0_
-    C, C, C, C, C, C, C, C, C, C, C, C, C, C, C, C, // 1_
-    W, P, P, P, P, P, P, P, P, P, P, P, P, P, P, P, // 2_
-    D, D, D, D, D, D, D, D, D, D, P, P, P, P, P, P, // 3_
-    P, Ux,Ux,Ux,Ux,Ux,Ux,U, U, U, U, U, U, U, U, U, // 4_
-    U, U, U, U, U, U, U, U, U, U, U, P, P, P, P, P, // 5_
-    P, Lx,Lx,Lx,Lx,Lx,Lx,L, L, L, L, L, L, L, L, L, // 6_
-    L, L, L, L, L, L, L, L, L, L, L, P, P, P, P, C, // 7_
-];
-
 #[cfg(test)]
 mod tests {
-    use super::*;
+    //! Note that most of these tests are not testing `AsciiExt` methods, but
+    //! test inherent ascii methods of char, u8, str and [u8]. `AsciiExt` is
+    //! just using those methods, though.
     use char::from_u32;
 
     #[test]
diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs
index 5cf1d225b90..429153dc58b 100644
--- a/src/libstd/lib.rs
+++ b/src/libstd/lib.rs
@@ -244,6 +244,7 @@
 #![feature(allow_internal_unstable)]
 #![feature(align_offset)]
 #![feature(array_error_internals)]
+#![feature(ascii_ctype)]
 #![feature(asm)]
 #![feature(attr_literals)]
 #![feature(box_syntax)]
diff --git a/src/libstd/path.rs b/src/libstd/path.rs
index 294743ed2cc..270878dc029 100644
--- a/src/libstd/path.rs
+++ b/src/libstd/path.rs
@@ -77,7 +77,6 @@
 
 #![stable(feature = "rust1", since = "1.0.0")]
 
-use ascii::*;
 use borrow::{Borrow, Cow};
 use cmp;
 use error::Error;
diff --git a/src/libstd/sys/windows/path.rs b/src/libstd/sys/windows/path.rs
index 2b47808451b..98d62a0c953 100644
--- a/src/libstd/sys/windows/path.rs
+++ b/src/libstd/sys/windows/path.rs
@@ -8,8 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use ascii::*;
-
 use path::Prefix;
 use ffi::OsStr;
 use mem;
diff --git a/src/libstd/sys/windows/process.rs b/src/libstd/sys/windows/process.rs
index 0d1766d5aec..631d69b05e1 100644
--- a/src/libstd/sys/windows/process.rs
+++ b/src/libstd/sys/windows/process.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use ascii::*;
+use ascii::AsciiExt;
 use collections::HashMap;
 use collections;
 use env::split_paths;
diff --git a/src/libstd_unicode/char.rs b/src/libstd_unicode/char.rs
index 5c0c7a4fbca..c012bdcb6db 100644
--- a/src/libstd_unicode/char.rs
+++ b/src/libstd_unicode/char.rs
@@ -923,6 +923,529 @@ impl char {
     pub fn to_uppercase(self) -> ToUppercase {
         ToUppercase(CaseMappingIter::new(conversions::to_upper(self)))
     }
+
+    /// Checks if the value is within the ASCII range.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let ascii = 'a';
+    /// let non_ascii = '❤';
+    ///
+    /// assert!(ascii.is_ascii());
+    /// assert!(!non_ascii.is_ascii());
+    /// ```
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[inline]
+    pub fn is_ascii(&self) -> bool {
+        *self as u32 <= 0x7F
+    }
+
+    /// Makes a copy of the value in its ASCII upper case equivalent.
+    ///
+    /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
+    /// but non-ASCII letters are unchanged.
+    ///
+    /// To uppercase the value in-place, use [`make_ascii_uppercase`].
+    ///
+    /// To uppercase ASCII characters in addition to non-ASCII characters, use
+    /// [`to_uppercase`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let ascii = 'a';
+    /// let non_ascii = '❤';
+    ///
+    /// assert_eq!('A', ascii.to_ascii_uppercase());
+    /// assert_eq!('❤', non_ascii.to_ascii_uppercase());
+    /// ```
+    ///
+    /// [`make_ascii_uppercase`]: #method.make_ascii_uppercase
+    /// [`to_uppercase`]: #method.to_uppercase
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[inline]
+    pub fn to_ascii_uppercase(&self) -> char {
+        if self.is_ascii() {
+            (*self as u8).to_ascii_uppercase() as char
+        } else {
+            *self
+        }
+    }
+
+    /// Makes a copy of the value in its ASCII lower case equivalent.
+    ///
+    /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
+    /// but non-ASCII letters are unchanged.
+    ///
+    /// To lowercase the value in-place, use [`make_ascii_lowercase`].
+    ///
+    /// To lowercase ASCII characters in addition to non-ASCII characters, use
+    /// [`to_lowercase`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let ascii = 'A';
+    /// let non_ascii = '❤';
+    ///
+    /// assert_eq!('a', ascii.to_ascii_lowercase());
+    /// assert_eq!('❤', non_ascii.to_ascii_lowercase());
+    /// ```
+    ///
+    /// [`make_ascii_lowercase`]: #method.make_ascii_lowercase
+    /// [`to_lowercase`]: #method.to_lowercase
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[inline]
+    pub fn to_ascii_lowercase(&self) -> char {
+        if self.is_ascii() {
+            (*self as u8).to_ascii_lowercase() as char
+        } else {
+            *self
+        }
+    }
+
+    /// Checks that two values are an ASCII case-insensitive match.
+    ///
+    /// Equivalent to `to_ascii_lowercase(a) == to_ascii_lowercase(b)`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let upper_a = 'A';
+    /// let lower_a = 'a';
+    /// let lower_z = 'z';
+    ///
+    /// assert!(upper_a.eq_ignore_ascii_case(&lower_a));
+    /// assert!(upper_a.eq_ignore_ascii_case(&upper_a));
+    /// assert!(!upper_a.eq_ignore_ascii_case(&lower_z));
+    /// ```
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[inline]
+    pub fn eq_ignore_ascii_case(&self, other: &char) -> bool {
+        self.to_ascii_lowercase() == other.to_ascii_lowercase()
+    }
+
+    /// Converts this type to its ASCII upper case equivalent in-place.
+    ///
+    /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
+    /// but non-ASCII letters are unchanged.
+    ///
+    /// To return a new uppercased value without modifying the existing one, use
+    /// [`to_ascii_uppercase`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let mut ascii = 'a';
+    ///
+    /// ascii.make_ascii_uppercase();
+    ///
+    /// assert_eq!('A', ascii);
+    /// ```
+    ///
+    /// [`to_ascii_uppercase`]: #method.to_ascii_uppercase
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[inline]
+    pub fn make_ascii_uppercase(&mut self) {
+        *self = self.to_ascii_uppercase();
+    }
+
+    /// Converts this type to its ASCII lower case equivalent in-place.
+    ///
+    /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
+    /// but non-ASCII letters are unchanged.
+    ///
+    /// To return a new lowercased value without modifying the existing one, use
+    /// [`to_ascii_lowercase`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let mut ascii = 'A';
+    ///
+    /// ascii.make_ascii_lowercase();
+    ///
+    /// assert_eq!('a', ascii);
+    /// ```
+    ///
+    /// [`to_ascii_lowercase`]: #method.to_ascii_lowercase
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[inline]
+    pub fn make_ascii_lowercase(&mut self) {
+        *self = self.to_ascii_lowercase();
+    }
+
+    /// Checks if the value is an ASCII alphabetic character:
+    ///
+    /// - U+0041 'A' ... U+005A 'Z', or
+    /// - U+0061 'a' ... U+007A 'z'.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(ascii_ctype)]
+    ///
+    /// let uppercase_a = 'A';
+    /// let uppercase_g = 'G';
+    /// let a = 'a';
+    /// let g = 'g';
+    /// let zero = '0';
+    /// let percent = '%';
+    /// let space = ' ';
+    /// let lf = '\n';
+    /// let esc: char = 0x1b_u8.into();
+    ///
+    /// assert!(uppercase_a.is_ascii_alphabetic());
+    /// assert!(uppercase_g.is_ascii_alphabetic());
+    /// assert!(a.is_ascii_alphabetic());
+    /// assert!(g.is_ascii_alphabetic());
+    /// assert!(!zero.is_ascii_alphabetic());
+    /// assert!(!percent.is_ascii_alphabetic());
+    /// assert!(!space.is_ascii_alphabetic());
+    /// assert!(!lf.is_ascii_alphabetic());
+    /// assert!(!esc.is_ascii_alphabetic());
+    /// ```
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_alphabetic(&self) -> bool {
+        self.is_ascii() && (*self as u8).is_ascii_alphabetic()
+    }
+
+    /// Checks if the value is an ASCII uppercase character:
+    /// U+0041 'A' ... U+005A 'Z'.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(ascii_ctype)]
+    ///
+    /// let uppercase_a = 'A';
+    /// let uppercase_g = 'G';
+    /// let a = 'a';
+    /// let g = 'g';
+    /// let zero = '0';
+    /// let percent = '%';
+    /// let space = ' ';
+    /// let lf = '\n';
+    /// let esc: char = 0x1b_u8.into();
+    ///
+    /// assert!(uppercase_a.is_ascii_uppercase());
+    /// assert!(uppercase_g.is_ascii_uppercase());
+    /// assert!(!a.is_ascii_uppercase());
+    /// assert!(!g.is_ascii_uppercase());
+    /// assert!(!zero.is_ascii_uppercase());
+    /// assert!(!percent.is_ascii_uppercase());
+    /// assert!(!space.is_ascii_uppercase());
+    /// assert!(!lf.is_ascii_uppercase());
+    /// assert!(!esc.is_ascii_uppercase());
+    /// ```
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_uppercase(&self) -> bool {
+        self.is_ascii() && (*self as u8).is_ascii_uppercase()
+    }
+
+    /// Checks if the value is an ASCII lowercase character:
+    /// U+0061 'a' ... U+007A 'z'.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(ascii_ctype)]
+    ///
+    /// let uppercase_a = 'A';
+    /// let uppercase_g = 'G';
+    /// let a = 'a';
+    /// let g = 'g';
+    /// let zero = '0';
+    /// let percent = '%';
+    /// let space = ' ';
+    /// let lf = '\n';
+    /// let esc: char = 0x1b_u8.into();
+    ///
+    /// assert!(!uppercase_a.is_ascii_lowercase());
+    /// assert!(!uppercase_g.is_ascii_lowercase());
+    /// assert!(a.is_ascii_lowercase());
+    /// assert!(g.is_ascii_lowercase());
+    /// assert!(!zero.is_ascii_lowercase());
+    /// assert!(!percent.is_ascii_lowercase());
+    /// assert!(!space.is_ascii_lowercase());
+    /// assert!(!lf.is_ascii_lowercase());
+    /// assert!(!esc.is_ascii_lowercase());
+    /// ```
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_lowercase(&self) -> bool {
+        self.is_ascii() && (*self as u8).is_ascii_lowercase()
+    }
+
+    /// Checks if the value is an ASCII alphanumeric character:
+    ///
+    /// - U+0041 'A' ... U+005A 'Z', or
+    /// - U+0061 'a' ... U+007A 'z', or
+    /// - U+0030 '0' ... U+0039 '9'.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(ascii_ctype)]
+    ///
+    /// let uppercase_a = 'A';
+    /// let uppercase_g = 'G';
+    /// let a = 'a';
+    /// let g = 'g';
+    /// let zero = '0';
+    /// let percent = '%';
+    /// let space = ' ';
+    /// let lf = '\n';
+    /// let esc: char = 0x1b_u8.into();
+    ///
+    /// assert!(uppercase_a.is_ascii_alphanumeric());
+    /// assert!(uppercase_g.is_ascii_alphanumeric());
+    /// assert!(a.is_ascii_alphanumeric());
+    /// assert!(g.is_ascii_alphanumeric());
+    /// assert!(zero.is_ascii_alphanumeric());
+    /// assert!(!percent.is_ascii_alphanumeric());
+    /// assert!(!space.is_ascii_alphanumeric());
+    /// assert!(!lf.is_ascii_alphanumeric());
+    /// assert!(!esc.is_ascii_alphanumeric());
+    /// ```
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_alphanumeric(&self) -> bool {
+        self.is_ascii() && (*self as u8).is_ascii_alphanumeric()
+    }
+
+    /// Checks if the value is an ASCII decimal digit:
+    /// U+0030 '0' ... U+0039 '9'.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(ascii_ctype)]
+    ///
+    /// let uppercase_a = 'A';
+    /// let uppercase_g = 'G';
+    /// let a = 'a';
+    /// let g = 'g';
+    /// let zero = '0';
+    /// let percent = '%';
+    /// let space = ' ';
+    /// let lf = '\n';
+    /// let esc: char = 0x1b_u8.into();
+    ///
+    /// assert!(!uppercase_a.is_ascii_digit());
+    /// assert!(!uppercase_g.is_ascii_digit());
+    /// assert!(!a.is_ascii_digit());
+    /// assert!(!g.is_ascii_digit());
+    /// assert!(zero.is_ascii_digit());
+    /// assert!(!percent.is_ascii_digit());
+    /// assert!(!space.is_ascii_digit());
+    /// assert!(!lf.is_ascii_digit());
+    /// assert!(!esc.is_ascii_digit());
+    /// ```
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_digit(&self) -> bool {
+        self.is_ascii() && (*self as u8).is_ascii_digit()
+    }
+
+    /// Checks if the value is an ASCII hexadecimal digit:
+    ///
+    /// - U+0030 '0' ... U+0039 '9', or
+    /// - U+0041 'A' ... U+0046 'F', or
+    /// - U+0061 'a' ... U+0066 'f'.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(ascii_ctype)]
+    ///
+    /// let uppercase_a = 'A';
+    /// let uppercase_g = 'G';
+    /// let a = 'a';
+    /// let g = 'g';
+    /// let zero = '0';
+    /// let percent = '%';
+    /// let space = ' ';
+    /// let lf = '\n';
+    /// let esc: char = 0x1b_u8.into();
+    ///
+    /// assert!(uppercase_a.is_ascii_hexdigit());
+    /// assert!(!uppercase_g.is_ascii_hexdigit());
+    /// assert!(a.is_ascii_hexdigit());
+    /// assert!(!g.is_ascii_hexdigit());
+    /// assert!(zero.is_ascii_hexdigit());
+    /// assert!(!percent.is_ascii_hexdigit());
+    /// assert!(!space.is_ascii_hexdigit());
+    /// assert!(!lf.is_ascii_hexdigit());
+    /// assert!(!esc.is_ascii_hexdigit());
+    /// ```
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_hexdigit(&self) -> bool {
+        self.is_ascii() && (*self as u8).is_ascii_hexdigit()
+    }
+
+    /// Checks if the value is an ASCII punctuation character:
+    ///
+    /// - U+0021 ... U+002F `! " # $ % & ' ( ) * + , - . /`, or
+    /// - U+003A ... U+0040 `: ; < = > ? @`, or
+    /// - U+005B ... U+0060 `[ \\ ] ^ _ \``, or
+    /// - U+007B ... U+007E `{ | } ~`
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(ascii_ctype)]
+    ///
+    /// let uppercase_a = 'A';
+    /// let uppercase_g = 'G';
+    /// let a = 'a';
+    /// let g = 'g';
+    /// let zero = '0';
+    /// let percent = '%';
+    /// let space = ' ';
+    /// let lf = '\n';
+    /// let esc: char = 0x1b_u8.into();
+    ///
+    /// assert!(!uppercase_a.is_ascii_punctuation());
+    /// assert!(!uppercase_g.is_ascii_punctuation());
+    /// assert!(!a.is_ascii_punctuation());
+    /// assert!(!g.is_ascii_punctuation());
+    /// assert!(!zero.is_ascii_punctuation());
+    /// assert!(percent.is_ascii_punctuation());
+    /// assert!(!space.is_ascii_punctuation());
+    /// assert!(!lf.is_ascii_punctuation());
+    /// assert!(!esc.is_ascii_punctuation());
+    /// ```
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_punctuation(&self) -> bool {
+        self.is_ascii() && (*self as u8).is_ascii_punctuation()
+    }
+
+    /// Checks if the value is an ASCII graphic character:
+    /// U+0021 '@' ... U+007E '~'.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(ascii_ctype)]
+    ///
+    /// let uppercase_a = 'A';
+    /// let uppercase_g = 'G';
+    /// let a = 'a';
+    /// let g = 'g';
+    /// let zero = '0';
+    /// let percent = '%';
+    /// let space = ' ';
+    /// let lf = '\n';
+    /// let esc: char = 0x1b_u8.into();
+    ///
+    /// assert!(uppercase_a.is_ascii_graphic());
+    /// assert!(uppercase_g.is_ascii_graphic());
+    /// assert!(a.is_ascii_graphic());
+    /// assert!(g.is_ascii_graphic());
+    /// assert!(zero.is_ascii_graphic());
+    /// assert!(percent.is_ascii_graphic());
+    /// assert!(!space.is_ascii_graphic());
+    /// assert!(!lf.is_ascii_graphic());
+    /// assert!(!esc.is_ascii_graphic());
+    /// ```
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_graphic(&self) -> bool {
+        self.is_ascii() && (*self as u8).is_ascii_graphic()
+    }
+
+    /// 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.
+    ///
+    /// 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
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(ascii_ctype)]
+    ///
+    /// let uppercase_a = 'A';
+    /// let uppercase_g = 'G';
+    /// let a = 'a';
+    /// let g = 'g';
+    /// let zero = '0';
+    /// let percent = '%';
+    /// let space = ' ';
+    /// let lf = '\n';
+    /// let esc: char = 0x1b_u8.into();
+    ///
+    /// assert!(!uppercase_a.is_ascii_whitespace());
+    /// assert!(!uppercase_g.is_ascii_whitespace());
+    /// assert!(!a.is_ascii_whitespace());
+    /// assert!(!g.is_ascii_whitespace());
+    /// assert!(!zero.is_ascii_whitespace());
+    /// assert!(!percent.is_ascii_whitespace());
+    /// assert!(space.is_ascii_whitespace());
+    /// assert!(lf.is_ascii_whitespace());
+    /// assert!(!esc.is_ascii_whitespace());
+    /// ```
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_whitespace(&self) -> bool {
+        self.is_ascii() && (*self as u8).is_ascii_whitespace()
+    }
+
+    /// 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.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(ascii_ctype)]
+    ///
+    /// let uppercase_a = 'A';
+    /// let uppercase_g = 'G';
+    /// let a = 'a';
+    /// let g = 'g';
+    /// let zero = '0';
+    /// let percent = '%';
+    /// let space = ' ';
+    /// let lf = '\n';
+    /// let esc: char = 0x1b_u8.into();
+    ///
+    /// assert!(!uppercase_a.is_ascii_control());
+    /// assert!(!uppercase_g.is_ascii_control());
+    /// assert!(!a.is_ascii_control());
+    /// assert!(!g.is_ascii_control());
+    /// assert!(!zero.is_ascii_control());
+    /// assert!(!percent.is_ascii_control());
+    /// assert!(!space.is_ascii_control());
+    /// assert!(lf.is_ascii_control());
+    /// assert!(esc.is_ascii_control());
+    /// ```
+    #[unstable(feature = "ascii_ctype", issue = "39658")]
+    #[inline]
+    pub fn is_ascii_control(&self) -> bool {
+        self.is_ascii() && (*self as u8).is_ascii_control()
+    }
 }
 
 /// An iterator that decodes UTF-16 encoded code points from an iterator of `u16`s.
diff --git a/src/libstd_unicode/lib.rs b/src/libstd_unicode/lib.rs
index e5a114caed0..65058b6554a 100644
--- a/src/libstd_unicode/lib.rs
+++ b/src/libstd_unicode/lib.rs
@@ -30,6 +30,7 @@
 #![deny(warnings)]
 #![no_std]
 
+#![feature(ascii_ctype)]
 #![feature(core_char_ext)]
 #![feature(str_internals)]
 #![feature(decode_utf8)]
diff --git a/src/libsyntax/feature_gate.rs b/src/libsyntax/feature_gate.rs
index 8b564605c1e..a69bf53ee14 100644
--- a/src/libsyntax/feature_gate.rs
+++ b/src/libsyntax/feature_gate.rs
@@ -35,7 +35,6 @@ use visit::{self, FnKind, Visitor};
 use parse::ParseSess;
 use symbol::Symbol;
 
-use std::ascii::AsciiExt;
 use std::env;
 
 macro_rules! set {
diff --git a/src/test/ui/deref-suggestion.stderr b/src/test/ui/deref-suggestion.stderr
index 5ad9c19fa8c..3ed3297e05e 100644
--- a/src/test/ui/deref-suggestion.stderr
+++ b/src/test/ui/deref-suggestion.stderr
@@ -10,8 +10,8 @@ error[E0308]: mismatched types
            - .escape_debug()
            - .escape_default()
            - .escape_unicode()
-           - .to_lowercase()
-           - .to_uppercase()
+           - .to_ascii_lowercase()
+           - .to_ascii_uppercase()
 
 error[E0308]: mismatched types
   --> $DIR/deref-suggestion.rs:23:10
diff --git a/src/tools/cargotest/main.rs b/src/tools/cargotest/main.rs
index 4f4960efc9b..a6c56a13076 100644
--- a/src/tools/cargotest/main.rs
+++ b/src/tools/cargotest/main.rs
@@ -165,6 +165,8 @@ fn run_cargo_test(cargo_path: &Path, crate_path: &Path, packages: &[&str]) -> bo
     let status = command
         // Disable rust-lang/cargo's cross-compile tests
         .env("CFG_DISABLE_CROSS_TESTS", "1")
+        // Relax #![deny(warnings)] in some crates
+        .env("RUSTFLAGS", "--cap-lints warn")
         .current_dir(crate_path)
         .status()
         .expect("");