std/rustc/rustpkg/syntax: Support the `extern mod = ...` form

This commit allows you to write:

 extern mod x = "a/b/c";

which means rustc will search in the RUST_PATH for a package with
ID a/b/c, and bind it to the name `x` if it's found.

Incidentally, move get_relative_to from back::rpath into std::path

4 files changed, 29 insertions, 8 deletions

diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index 435be3c71af..17247222c3f 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -951,7 +951,11 @@ pub struct view_item {
 
 #[deriving(Clone, Eq, Encodable, Decodable, IterBytes)]
 pub enum view_item_ {
-    view_item_extern_mod(ident, ~[@MetaItem], NodeId),
+    // ident: name used to refer to this crate in the code
+    // optional @str: if present, this is a location (containing
+    // arbitrary characters) from which to fetch the crate sources
+    // For example, extern mod whatever = "github.com/mozilla/rust"
+    view_item_extern_mod(ident, Option<@str>, ~[@MetaItem], NodeId),
     view_item_use(~[@view_path]),
 }
 
diff --git a/src/libsyntax/ast_util.rs b/src/libsyntax/ast_util.rs
index ba167fe6714..9a8a3bc25d8 100644
--- a/src/libsyntax/ast_util.rs
+++ b/src/libsyntax/ast_util.rs
@@ -419,7 +419,7 @@ impl Visitor<()> for IdVisitor {
 
     fn visit_view_item(@mut self, view_item: &view_item, env: ()) {
         match view_item.node {
-            view_item_extern_mod(_, _, node_id) => {
+            view_item_extern_mod(_, _, _, node_id) => {
                 (self.visit_callback)(node_id)
             }
             view_item_use(ref view_paths) => {
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 4902c4587ac..5240edf00f1 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -4169,8 +4169,16 @@ impl Parser {
                                  self.this_token_to_str()));
         }
 
-        let (sort, ident) = match *self.token {
-            token::IDENT(*) => (ast::named, self.parse_ident()),
+        let (sort, maybe_path, ident) = match *self.token {
+            token::IDENT(*) => {
+                let the_ident = self.parse_ident();
+                let path = if *self.token == token::EQ {
+                    self.bump();
+                    Some(self.parse_str())
+                }
+                else { None };
+                (ast::named, path, the_ident)
+            }
             _ => {
                 if must_be_named_mod {
                     self.span_fatal(*self.span,
@@ -4179,7 +4187,7 @@ impl Parser {
                                          self.this_token_to_str()));
                 }
 
-                (ast::anonymous,
+                (ast::anonymous, None,
                  special_idents::clownshoes_foreign_mod)
             }
         };
@@ -4218,7 +4226,7 @@ impl Parser {
         let metadata = self.parse_optional_meta();
         self.expect(&token::SEMI);
         iovi_view_item(ast::view_item {
-            node: view_item_extern_mod(ident, metadata, self.get_id()),
+            node: view_item_extern_mod(ident, maybe_path, metadata, self.get_id()),
             attrs: attrs,
             vis: visibility,
             span: mk_sp(lo, self.last_span.hi)
@@ -4800,8 +4808,13 @@ impl Parser {
         } else if self.eat_keyword(keywords::Extern) {
             self.expect_keyword(keywords::Mod);
             let ident = self.parse_ident();
+            let path = if *self.token == token::EQ {
+                self.bump();
+                Some(self.parse_str())
+            }
+            else { None };
             let metadata = self.parse_optional_meta();
-            view_item_extern_mod(ident, metadata, self.get_id())
+            view_item_extern_mod(ident, path, metadata, self.get_id())
         } else {
             self.bug("expected view item");
         };
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index f517179f603..ffe9575a864 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -1856,9 +1856,13 @@ pub fn print_view_item(s: @ps, item: &ast::view_item) {
     print_outer_attributes(s, item.attrs);
     print_visibility(s, item.vis);
     match item.node {
-        ast::view_item_extern_mod(id, ref mta, _) => {
+        ast::view_item_extern_mod(id, ref optional_path, ref mta, _) => {
             head(s, "extern mod");
             print_ident(s, id);
+            for p in optional_path.iter() {
+                word(s.s, "=");
+                print_string(s, *p);
+            }
             if !mta.is_empty() {
                 popen(s);
                 commasep(s, consistent, *mta, |p, &i| print_meta_item(p, i));