Copy `AsciiExt` methods to `str` directly

This is done in order to deprecate AsciiExt eventually. Note that
this commit contains a bunch of `cfg(stage0)` statements. This is
due to a new compiler feature this commit depends on: the
`slice_u8` lang item. Once this lang item is available in the
stage0 compiler, all those cfg flags (and more) can be removed.

4 files changed, 290 insertions, 5 deletions

diff --git a/src/liballoc/slice.rs b/src/liballoc/slice.rs
index 8268528acbd..7590003a681 100644
--- a/src/liballoc/slice.rs
+++ b/src/liballoc/slice.rs
@@ -1533,7 +1533,7 @@ impl<T> [T] {
     }
 }
 
-// TODO(LukasKalbertodt): the `not(stage0)` constraint can be removed in the
+// 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"]
diff --git a/src/liballoc/str.rs b/src/liballoc/str.rs
index 895607ff8d4..2c257b8c736 100644
--- a/src/liballoc/str.rs
+++ b/src/liballoc/str.rs
@@ -2070,6 +2070,282 @@ 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'.
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[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
+    ///
+    /// ```
+    /// // 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());
+    /// ```
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[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
+    ///
+    /// ```
+    /// // 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());
+    /// ```
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[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'.
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[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'.
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[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'.
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[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 `{ | } ~`
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[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 '~'.
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[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
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[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.
+    #[stable(feature = "ascii_methods_on_intrinsics", since = "1.21.0")]
+    #[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/libstd/ascii.rs b/src/libstd/ascii.rs
index 7a474c1f254..200264a2583 100644
--- a/src/libstd/ascii.rs
+++ b/src/libstd/ascii.rs
@@ -298,6 +298,10 @@ pub trait AsciiExt {
     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;
@@ -389,9 +393,9 @@ impl AsciiExt for str {
     }
 }
 
-// TODO(LukasKalbertodt): this impl block can be removed in the future. This is
+// 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 TODO comment further down.
+// ascii methods for `[u8]`. See FIXME comment further down.
 #[cfg(stage0)]
 #[stable(feature = "rust1", since = "1.0.0")]
 impl AsciiExt for [u8] {
@@ -546,12 +550,18 @@ macro_rules! impl_by_delegating {
 impl_by_delegating!(u8, u8);
 impl_by_delegating!(char, char);
 
-// TODO(LukasKalbertodt): the macro invocation should replace the impl block
+// 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>);
 
+// 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.
 ///
 /// This `struct` is created by the [`escape_default`] function. See its
diff --git a/src/libsyntax/feature_gate.rs b/src/libsyntax/feature_gate.rs
index 30451ec757a..195aac5292f 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 {