auto merge of #19252 : japaric/rust/cow, r=aturon

- Add `IntoCow` trait, and put it in the prelude
- Add `is_owned`/`is_borrowed` methods to `Cow`
- Add `CowString`/`CowVec` type aliases (to `Cow<'_, String, str>`/`Cow<'_, Vec, [T]>` respectively)
- `Cow` implements: `Show`, `Hash`, `[Partial]{Eq,Ord}`
- `impl BorrowFrom<Cow<'a, T, B>> for B`

[breaking-change]s:

- `IntoMaybeOwned` has been removed from the prelude
- libcollections: `SendStr` is now an alias to `CowString<'static>` (it was aliased to `MaybeOwned<'static>`)
- libgraphviz:
  - `LabelText` variants now wrap `CowString` instead of `MaybeOwned`
  - `Nodes` and `Edges` are now type aliases to `CowVec` (they were aliased to `MaybeOwnedVec`)
- libstd/path: `Display::as_maybe_owned` has been renamed to `Display::as_cow` and now returns a `CowString`
- These functions now accept/return `Cow` instead of `MaybeOwned[Vector]`:
  - libregex: `Replacer::reg_replace`
  - libcollections: `str::from_utf8_lossy`
  - libgraphviz: `Id::new`, `Id::name`, `LabelText::pre_escaped_content`
  - libstd: `TaskBuilder::named`

r? @aturon 

2 files changed, 6 insertions, 6 deletions

diff --git a/src/libsyntax/parse/lexer/mod.rs b/src/libsyntax/parse/lexer/mod.rs
index a88029e087b..b5358e7d485 100644
--- a/src/libsyntax/parse/lexer/mod.rs
+++ b/src/libsyntax/parse/lexer/mod.rs
@@ -272,13 +272,13 @@ impl<'a> StringReader<'a> {
 
     /// Converts CRLF to LF in the given string, raising an error on bare CR.
     fn translate_crlf<'a>(&self, start: BytePos,
-                          s: &'a str, errmsg: &'a str) -> str::MaybeOwned<'a> {
+                          s: &'a str, errmsg: &'a str) -> str::CowString<'a> {
         let mut i = 0u;
         while i < s.len() {
             let str::CharRange { ch, next } = s.char_range_at(i);
             if ch == '\r' {
                 if next < s.len() && s.char_at(next) == '\n' {
-                    return translate_crlf_(self, start, s, errmsg, i).into_maybe_owned();
+                    return translate_crlf_(self, start, s, errmsg, i).into_cow();
                 }
                 let pos = start + BytePos(i as u32);
                 let end_pos = start + BytePos(next as u32);
@@ -286,7 +286,7 @@ impl<'a> StringReader<'a> {
             }
             i = next;
         }
-        return s.into_maybe_owned();
+        return s.into_cow();
 
         fn translate_crlf_(rdr: &StringReader, start: BytePos,
                         s: &str, errmsg: &str, mut i: uint) -> String {
@@ -550,7 +550,7 @@ impl<'a> StringReader<'a> {
                 let string = if has_cr {
                     self.translate_crlf(start_bpos, string,
                                         "bare CR not allowed in block doc-comment")
-                } else { string.into_maybe_owned() };
+                } else { string.into_cow() };
                 token::DocComment(token::intern(string.as_slice()))
             } else {
                 token::Comment
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index a9306c71240..c731a0005f8 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -4966,10 +4966,10 @@ impl<'a> Parser<'a> {
                 let mut err = String::from_str("circular modules: ");
                 let len = included_mod_stack.len();
                 for p in included_mod_stack.slice(i, len).iter() {
-                    err.push_str(p.display().as_maybe_owned().as_slice());
+                    err.push_str(p.display().as_cow().as_slice());
                     err.push_str(" -> ");
                 }
-                err.push_str(path.display().as_maybe_owned().as_slice());
+                err.push_str(path.display().as_cow().as_slice());
                 self.span_fatal(id_sp, err.as_slice());
             }
             None => ()