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

1 files changed, 7 insertions, 2 deletions

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));