Remove unused AsciiExt imports and fix tests related to ascii methods

Many AsciiExt imports have become useless thanks to the inherent ascii
methods added in the last commits. These were removed. In some places, I
fully specified the ascii method being called to enforce usage of the
AsciiExt trait. Note that some imports are not removed but tagged with
a `#[cfg(stage0)]` attribute. This is necessary, because certain ascii
methods are not yet available in stage0. All those imports will be
removed later.

Additionally, failing tests were fixed. The test suite should exit
successfully now.

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())
 });
 

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");

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);

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();
     ///

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);

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]);
     }
 }
-
-

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));

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;

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;

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;

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}"`
@@ -681,7 +681,9 @@ impl fmt::Debug for EscapeDefault {
 
 #[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]

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