rustc: Add support for `extern crate foo as bar`

The compiler will now issue a warning for crates that have syntax of the form
`extern crate "foo" as bar`, but it will still continue to accept this syntax.
Additionally, the string `foo-bar` will match the crate name `foo_bar` to assist
in the transition period as well.

This patch will land hopefully in tandem with a Cargo patch that will start
translating all crate names to have underscores instead of hyphens.

cc #23533

6 files changed, 31 insertions, 28 deletions

diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index 704abc43f10..fec67c7aef4 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -1771,8 +1771,8 @@ pub struct Item {
 pub enum Item_ {
     /// An`extern crate` item, with optional original crate name,
     ///
-    /// e.g. `extern crate foo` or `extern crate "foo-bar" as foo`
-    ItemExternCrate(Option<(InternedString, StrStyle)>),
+    /// e.g. `extern crate foo` or `extern crate foo_bar as foo`
+    ItemExternCrate(Option<Name>),
     /// A `use` or `pub use` item
     ItemUse(P<ViewPath>),
 
diff --git a/src/libsyntax/parse/mod.rs b/src/libsyntax/parse/mod.rs
index 968d2fd7e2a..4e851761212 100644
--- a/src/libsyntax/parse/mod.rs
+++ b/src/libsyntax/parse/mod.rs
@@ -1060,7 +1060,7 @@ mod test {
         let vitem_s = item_to_string(&*vitem);
         assert_eq!(&vitem_s[..], ex_s);
 
-        let ex_s = "extern crate \"foo\" as bar;";
+        let ex_s = "extern crate foo as bar;";
         let vitem = string_to_item(ex_s.to_string()).unwrap();
         let vitem_s = item_to_string(&*vitem);
         assert_eq!(&vitem_s[..], ex_s);
diff --git a/src/libsyntax/parse/obsolete.rs b/src/libsyntax/parse/obsolete.rs
index 7da0a6de547..276be73823a 100644
--- a/src/libsyntax/parse/obsolete.rs
+++ b/src/libsyntax/parse/obsolete.rs
@@ -24,6 +24,7 @@ use ptr::P;
 pub enum ObsoleteSyntax {
     ClosureKind,
     EmptyIndex,
+    ExternCrateString,
 }
 
 pub trait ParserObsoleteMethods {
@@ -56,6 +57,11 @@ impl<'a> ParserObsoleteMethods for parser::Parser<'a> {
                 "write `[..]` instead",
                 false, // warning for now
             ),
+            ObsoleteSyntax::ExternCrateString => (
+                "\"crate-name\"",
+                "use an identifier not in quotes instead",
+                false, // warning for now
+            ),
         };
 
         self.report(sp, kind, kind_str, desc, error);
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 4ae5e0faa31..fe259d0bf78 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -4986,37 +4986,28 @@ impl<'a> Parser<'a> {
                                 attrs: Vec<Attribute>)
                                 -> P<Item> {
 
-        let span = self.span;
         let (maybe_path, ident) = match self.token {
             token::Ident(..) => {
-                let the_ident = self.parse_ident();
-                let path = if self.eat_keyword_noexpect(keywords::As) {
-                    // skip the ident if there is one
-                    if self.token.is_ident() { self.bump(); }
-
-                    self.span_err(span, "expected `;`, found `as`");
-                    self.fileline_help(span,
-                                   &format!("perhaps you meant to enclose the crate name `{}` in \
-                                           a string?",
-                                          the_ident.as_str()));
-                    None
+                let crate_name = self.parse_ident();
+                if self.eat_keyword(keywords::As) {
+                    (Some(crate_name.name), self.parse_ident())
                 } else {
-                    None
-                };
-                self.expect(&token::Semi);
-                (path, the_ident)
+                    (None, crate_name)
+                }
             },
-            token::Literal(token::Str_(..), suf) | token::Literal(token::StrRaw(..), suf) => {
+            token::Literal(token::Str_(..), suf) |
+            token::Literal(token::StrRaw(..), suf) => {
                 let sp = self.span;
                 self.expect_no_suffix(sp, "extern crate name", suf);
                 // forgo the internal suffix check of `parse_str` to
                 // avoid repeats (this unwrap will always succeed due
                 // to the restriction of the `match`)
-                let (s, style, _) = self.parse_optional_str().unwrap();
+                let (s, _, _) = self.parse_optional_str().unwrap();
                 self.expect_keyword(keywords::As);
                 let the_ident = self.parse_ident();
-                self.expect(&token::Semi);
-                (Some((s, style)), the_ident)
+                self.obsolete(sp, ObsoleteSyntax::ExternCrateString);
+                let s = token::intern(&s);
+                (Some(s), the_ident)
             },
             _ => {
                 let span = self.span;
@@ -5027,6 +5018,7 @@ impl<'a> Parser<'a> {
                                         token_str));
             }
         };
+        self.expect(&token::Semi);
 
         let last_span = self.last_span;
         self.mk_item(lo,
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index 828d085fd43..f6213b7db40 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -821,8 +821,13 @@ impl<'a> State<'a> {
             ast::ItemExternCrate(ref optional_path) => {
                 try!(self.head(&visibility_qualified(item.vis,
                                                      "extern crate")));
-                if let Some((ref p, style)) = *optional_path {
-                    try!(self.print_string(p, style));
+                if let Some(p) = *optional_path {
+                    let val = token::get_name(p);
+                    if val.contains("-") {
+                        try!(self.print_string(&val, ast::CookedStr));
+                    } else {
+                        try!(self.print_name(p));
+                    }
                     try!(space(&mut self.s));
                     try!(word(&mut self.s, "as"));
                     try!(space(&mut self.s));
diff --git a/src/libsyntax/std_inject.rs b/src/libsyntax/std_inject.rs
index ac7cdb1b413..0fa7e4f902c 100644
--- a/src/libsyntax/std_inject.rs
+++ b/src/libsyntax/std_inject.rs
@@ -54,8 +54,8 @@ impl fold::Folder for StandardLibraryInjector {
 
         // The name to use in `extern crate "name" as std;`
         let actual_crate_name = match self.alt_std_name {
-            Some(ref s) => token::intern_and_get_ident(&s[..]),
-            None => token::intern_and_get_ident("std"),
+            Some(ref s) => token::intern(&s),
+            None => token::intern("std"),
         };
 
         krate.module.items.insert(0, P(ast::Item {
@@ -64,7 +64,7 @@ impl fold::Folder for StandardLibraryInjector {
             attrs: vec!(
                 attr::mk_attr_outer(attr::mk_attr_id(), attr::mk_word_item(
                         InternedString::new("macro_use")))),
-            node: ast::ItemExternCrate(Some((actual_crate_name, ast::CookedStr))),
+            node: ast::ItemExternCrate(Some(actual_crate_name)),
             vis: ast::Inherited,
             span: DUMMY_SP
         }));