Rollup merge of rust-lang#23461 - alexcrichton:feat-char-at, r=aturon

 This commit clarifies some of the unstable features in the `str` module by
moving them out of the blanket `core` and `collections` features.

The following methods were moved to the `str_char` feature which generally
encompasses decoding specific characters from a `str` and dealing with the
result. It is unclear if any of these methods need to be stabilized for 1.0 and
the most conservative route for now is to continue providing them but to leave
them as unstable under a more specific name.

* `is_char_boundary`
* `char_at`
* `char_range_at`
* `char_at_reverse`
* `char_range_at_reverse`
* `slice_shift_char`

The following methods were moved into the generic `unicode` feature as they are
specifically enabled by the `unicode` crate itself.

* `nfd_chars`
* `nfkd_chars`
* `nfc_chars`
* `graphemes`
* `grapheme_indices`
* `width`

src/compiletest/runtest.rs

@@ -1052,22 +1052,22 @@ fn scan_char(haystack: &str, needle: char, idx: &mut uint) -> bool {
     if *idx >= haystack.len() {
         return false;
     }
-    let range = haystack.char_range_at(*idx);
-    if range.ch != needle {
+    let ch = haystack.char_at(*idx);
+    if ch != needle {
         return false;
     }
-    *idx = range.next;
+    *idx += ch.len_utf8();
     return true;
 }
 
 fn scan_integer(haystack: &str, idx: &mut uint) -> bool {
     let mut i = *idx;
     while i < haystack.len() {
-        let range = haystack.char_range_at(i);
-        if range.ch < '0' || '9' < range.ch {
+        let ch = haystack.char_at(i);
+        if ch < '0' || '9' < ch {
             break;
         }
-        i = range.next;
+        i += ch.len_utf8();
     }
     if i == *idx {
         return false;
@@ -1083,9 +1083,9 @@ fn scan_string(haystack: &str, needle: &str, idx: &mut uint) -> bool {
         if haystack_i >= haystack.len() {
             return false;
         }
-        let range = haystack.char_range_at(haystack_i);
-        haystack_i = range.next;
-        if !scan_char(needle, range.ch, &mut needle_i) {
+        let ch = haystack.char_at(haystack_i);
+        haystack_i += ch.len_utf8();
+        if !scan_char(needle, ch, &mut needle_i) {
             return false;
         }
     }

src/libcollections/lib.rs

@@ -35,6 +35,7 @@
 #![feature(unique)]
 #![feature(unsafe_no_drop_flag)]
 #![feature(step_by)]
+#![feature(str_char)]
 #![cfg_attr(test, feature(rand, rustc_private, test))]
 #![cfg_attr(test, allow(deprecated))] // rand
 

src/libcollections/string.rs

@@ -29,7 +29,7 @@ use unicode::str as unicode_str;
 use unicode::str::Utf16Item;
 
 use borrow::{Cow, IntoCow};
-use str::{self, CharRange, FromStr, Utf8Error};
+use str::{self, FromStr, Utf8Error};
 use vec::{DerefVec, Vec, as_vec};
 
 /// A growable string stored as a UTF-8 encoded buffer.
@@ -561,9 +561,9 @@ impl String {
             return None
         }
 
-        let CharRange {ch, next} = self.char_range_at_reverse(len);
+        let ch = self.char_at_reverse(len);
         unsafe {
-            self.vec.set_len(next);
+            self.vec.set_len(len - ch.len_utf8());
         }
         Some(ch)
     }
@@ -595,7 +595,8 @@ impl String {
         let len = self.len();
         assert!(idx <= len);
 
-        let CharRange { ch, next } = self.char_range_at(idx);
+        let ch = self.char_at(idx);
+        let next = idx + ch.len_utf8();
         unsafe {
             ptr::copy(self.vec.as_mut_ptr().offset(idx as isize),
                       self.vec.as_ptr().offset(next as isize),

src/libcore/str/mod.rs

@@ -18,6 +18,7 @@
 
 use self::OldSearcher::{TwoWay, TwoWayLong};
 
+use char::CharExt;
 use clone::Clone;
 use cmp::{self, Eq};
 use default::Default;
@@ -1112,8 +1113,10 @@ static UTF8_CHAR_WIDTH: [u8; 256] = [
 /// the next `char` in a string.  This can be used as a data structure
 /// for iterating over the UTF-8 bytes of a string.
 #[derive(Copy)]
-#[unstable(feature = "core",
-           reason = "naming is uncertain with container conventions")]
+#[unstable(feature = "str_char",
+           reason = "existence of this struct is uncertain as it is frequently \
+                     able to be replaced with char.len_utf8() and/or \
+                     char/char_indices iterators")]
 pub struct CharRange {
     /// Current `char`
     pub ch: char,
@@ -1646,8 +1649,8 @@ impl StrExt for str {
         if self.is_empty() {
             None
         } else {
-            let CharRange {ch, next} = self.char_range_at(0);
-            let next_s = unsafe { self.slice_unchecked(next, self.len()) };
+            let ch = self.char_at(0);
+            let next_s = unsafe { self.slice_unchecked(ch.len_utf8(), self.len()) };
             Some((ch, next_s))
         }
     }

src/libgetopts/lib.rs

@@ -92,11 +92,10 @@
        html_playground_url = "http://play.rust-lang.org/")]
 
 #![deny(missing_docs)]
-#![feature(collections)]
 #![feature(int_uint)]
 #![feature(staged_api)]
-#![feature(core)]
 #![feature(str_words)]
+#![feature(str_char)]
 #![cfg_attr(test, feature(rustc_private))]
 
 #[cfg(test)] #[macro_use] extern crate log;
@@ -620,8 +619,8 @@ pub fn getopts(args: &[String], optgrps: &[OptGroup]) -> Result {
                 let mut j = 1;
                 names = Vec::new();
                 while j < curlen {
-                    let range = cur.char_range_at(j);
-                    let opt = Short(range.ch);
+                    let ch = cur.char_at(j);
+                    let opt = Short(ch);
 
                     /* In a series of potential options (eg. -aheJ), if we
                        see one which takes an argument, we assume all
@@ -642,12 +641,13 @@ pub fn getopts(args: &[String], optgrps: &[OptGroup]) -> Result {
                         No => false
                     };
 
-                    if arg_follows && range.next < curlen {
-                        i_arg = Some((&cur[range.next..curlen]).to_string());
+                    let next = j + ch.len_utf8();
+                    if arg_follows && next < curlen {
+                        i_arg = Some((&cur[next..curlen]).to_string());
                         break;
                     }
 
-                    j = range.next;
+                    j = next;
                 }
             }
             let mut name_pos = 0;

src/librustc/lib.rs

@@ -42,6 +42,7 @@
 #![feature(io)]
 #![feature(path_ext)]
 #![feature(str_words)]
+#![feature(str_char)]
 #![cfg_attr(test, feature(test))]
 
 extern crate arena;

src/librustc_driver/lib.rs

@@ -38,6 +38,7 @@
 #![feature(exit_status)]
 #![feature(io)]
 #![feature(set_stdio)]
+#![feature(unicode)]
 
 extern crate arena;
 extern crate flate;

src/librustc_lint/lib.rs

@@ -41,6 +41,7 @@
 #![feature(unsafe_destructor)]
 #![feature(staged_api)]
 #![feature(std_misc)]
+#![feature(str_char)]
 #![cfg_attr(test, feature(test))]
 
 extern crate syntax;

src/libserialize/lib.rs

@@ -37,6 +37,7 @@ Core encoding and decoding interfaces.
 #![feature(staged_api)]
 #![feature(std_misc)]
 #![feature(unicode)]
+#![feature(str_char)]
 #![cfg_attr(test, feature(test))]
 
 // test harness access

src/libstd/lib.rs

@@ -127,6 +127,7 @@
 #![feature(int_uint)]
 #![feature(unique)]
 #![feature(allow_internal_unstable)]
+#![feature(str_char)]
 #![cfg_attr(test, feature(test, rustc_private))]
 
 // Don't link to std. We are std.

src/libsyntax/lib.rs

@@ -38,6 +38,7 @@
 #![feature(std_misc)]
 #![feature(unicode)]
 #![feature(path_ext)]
+#![feature(str_char)]
 
 extern crate arena;
 extern crate fmt_macros;

src/libsyntax/parse/lexer/comments.rs

@@ -20,7 +20,6 @@ use parse::lexer;
 use print::pprust;
 
 use std::io::Read;
-use std::str;
 use std::usize;
 
 #[derive(Clone, Copy, PartialEq)]
@@ -210,11 +209,11 @@ fn all_whitespace(s: &str, col: CharPos) -> Option<usize> {
     let mut col = col.to_usize();
     let mut cursor: usize = 0;
     while col > 0 && cursor < len {
-        let r: str::CharRange = s.char_range_at(cursor);
-        if !r.ch.is_whitespace() {
+        let ch = s.char_at(cursor);
+        if !ch.is_whitespace() {
             return None;
         }
-        cursor = r.next;
+        cursor += ch.len_utf8();
         col -= 1;
     }
     return Some(cursor);

src/libsyntax/parse/lexer/mod.rs

@@ -22,7 +22,6 @@ use std::fmt;
 use std::mem::replace;
 use std::num;
 use std::rc::Rc;
-use std::str;
 
 pub use ext::tt::transcribe::{TtReader, new_tt_reader, new_tt_reader_with_doc_flag};
 
@@ -291,7 +290,8 @@ impl<'a> StringReader<'a> {
                           s: &'b str, errmsg: &'b str) -> Cow<'b, str> {
         let mut i = 0;
         while i < s.len() {
-            let str::CharRange { ch, next } = s.char_range_at(i);
+            let ch = s.char_at(i);
+            let next = i + ch.len_utf8();
             if ch == '\r' {
                 if next < s.len() && s.char_at(next) == '\n' {
                     return translate_crlf_(self, start, s, errmsg, i).into_cow();
@@ -309,7 +309,8 @@ impl<'a> StringReader<'a> {
             let mut buf = String::with_capacity(s.len());
             let mut j = 0;
             while i < s.len() {
-                let str::CharRange { ch, next } = s.char_range_at(i);
+                let ch = s.char_at(i);
+                let next = i + ch.len_utf8();
                 if ch == '\r' {
                     if j < i { buf.push_str(&s[j..i]); }
                     j = next;
@@ -335,10 +336,11 @@ impl<'a> StringReader<'a> {
         if current_byte_offset < self.source_text.len() {
             assert!(self.curr.is_some());
             let last_char = self.curr.unwrap();
-            let next = self.source_text.char_range_at(current_byte_offset);
-            let byte_offset_diff = next.next - current_byte_offset;
+            let ch = self.source_text.char_at(current_byte_offset);
+            let next = current_byte_offset + ch.len_utf8();
+            let byte_offset_diff = next - current_byte_offset;
             self.pos = self.pos + Pos::from_usize(byte_offset_diff);
-            self.curr = Some(next.ch);
+            self.curr = Some(ch);
             self.col = self.col + CharPos(1);
             if last_char == '\n' {
                 self.filemap.next_line(self.last_pos);
@@ -370,7 +372,7 @@ impl<'a> StringReader<'a> {
         let offset = self.byte_offset(self.pos).to_usize();
         let s = &self.source_text[..];
         if offset >= s.len() { return None }
-        let str::CharRange { next, .. } = s.char_range_at(offset);
+        let next = offset + s.char_at(offset).len_utf8();
         if next < s.len() {
             Some(s.char_at(next))
         } else {

src/libterm/lib.rs

@@ -60,6 +60,7 @@
 #![feature(rustc_private)]
 #![feature(staged_api)]
 #![feature(std_misc)]
+#![feature(str_char)]
 #![feature(path_ext)]
 #![cfg_attr(windows, feature(libc))]
 

src/libunicode/u_str.rs

@@ -244,7 +244,7 @@ impl<'a> Iterator for Graphemes<'a> {
         }
 
         self.cat = if take_curr {
-            idx = self.string.char_range_at(idx).next;
+            idx = idx + len_utf8(self.string.char_at(idx));
             None
         } else {
             Some(cat)
@@ -256,6 +256,11 @@ impl<'a> Iterator for Graphemes<'a> {
     }
 }
 
+#[cfg(stage0)]
+fn len_utf8(c: char) -> usize { UCharExt::len_utf8(c) }
+#[cfg(not(stage0))]
+fn len_utf8(c: char) -> usize { c.len_utf8() }
+
 impl<'a> DoubleEndedIterator for Graphemes<'a> {
     #[inline]
     fn next_back(&mut self) -> Option<&'a str> {