WIP on issue 1426 (exporting all tags)

Support Lenny222's proposed syntax for exporting a tag without
its variants, or selected tags from a variant, in the AST and parser.
No support further down the line yet. Tests are xfailed.

src/comp/syntax/ast.rs

@@ -439,6 +439,10 @@ enum view_item_ {
     view_item_import_glob(@simple_path, node_id),
     view_item_import_from(@simple_path, [import_ident], node_id),
     view_item_export([ident], node_id),
+    // export foo::{}
+    view_item_export_tag_none(ident, node_id),
+    // export foo::{bar, baz, blat}
+    view_item_export_tag_some(ident, [ident], node_id)
 }
 
 // Meta-data associated with an item

src/comp/syntax/parse/parser.rs

@@ -2391,11 +2391,35 @@ fn parse_import(p: parser) -> ast::view_item_ {
     }
 }
 
+fn parse_tag_export(p:parser, tyname:ast::ident) -> ast::view_item_ {
+    let tagnames:[ast::ident] =
+        parse_seq(token::LBRACE, token::RBRACE,
+                    seq_sep(token::COMMA), {|p| parse_ident(p) }, p).node;
+    let id = p.get_id();
+    if vec::is_empty(tagnames) {
+       ret ast::view_item_export_tag_none(tyname, id);
+    }
+    else {
+       ret ast::view_item_export_tag_some(tyname, tagnames, id);
+    }
+}
+
 fn parse_export(p: parser) -> ast::view_item_ {
-    let ids =
-        parse_seq_to_before_end(token::SEMI, seq_sep(token::COMMA),
-                                parse_ident, p);
-    ret ast::view_item_export(ids, p.get_id());
+    let first = parse_ident(p);
+    alt p.token {
+       token::COLON {
+           p.bump();
+           expect(p, token::COLON);
+           ret parse_tag_export(p, first);
+       }
+       t {
+           if t == token::COMMA { p.bump(); }
+           let ids =
+               parse_seq_to_before_end(token::SEMI, seq_sep(token::COMMA),
+                                       parse_ident, p);
+           ret ast::view_item_export(vec::concat([[first], ids]), p.get_id());
+       }
+    }
 }
 
 fn parse_view_item(p: parser) -> @ast::view_item {

src/test/compile-fail/tag-exports-2.rs

@@ -0,0 +1,18 @@
+// xfail-test
+mod alder {
+  export burnside;
+  export everett::{flanders};
+  export irving::{johnson, kearney};
+  export marshall::{};
+
+  tag burnside { couch, davis }
+  tag everett { flanders, glisan, hoyt }
+  tag irving { johnson, kearney, lovejoy }
+  tag marshall { northrup, overton }
+}
+
+import alder::*;
+
+fn main() {
+  let raleigh: irving = lovejoy;
+}

src/test/compile-fail/tag-exports-3.rs

@@ -0,0 +1,19 @@
+// xfail-test
+mod alder {
+  export burnside;
+  export everett::{flanders};
+  export irving::{johnson, kearney};
+  export marshall::{};
+
+  tag burnside { couch, davis }
+  tag everett { flanders, glisan, hoyt }
+  tag irving { johnson, kearney, lovejoy }
+  tag marshall { northrup, overton }
+}
+
+import alder::*;
+
+fn main() {
+  let savier: marshall = northrup;
+
+}

src/test/compile-fail/tag-exports.rs

@@ -0,0 +1,18 @@
+// xfail-test
+mod alder {
+  export burnside;
+  export everett::{flanders};
+  export irving::{johnson, kearney};
+  export marshall::{};
+
+  tag burnside { couch, davis }
+  tag everett { flanders, glisan, hoyt }
+  tag irving { johnson, kearney, lovejoy }
+  tag marshall { northrup, overton }
+}
+
+import alder::*;
+
+fn main() {
+  let quimby: everett = glisan;
+}

src/test/run-pass/tag-exports.rs

@@ -0,0 +1,21 @@
+// xfail-test
+mod alder {
+  export burnside;
+  export everett::{flanders};
+  export irving::{johnson, kearney};
+  export marshall::{};
+
+  tag burnside { couch, davis }
+  tag everett { flanders, glisan, hoyt }
+  tag irving { johnson, kearney, lovejoy }
+  tag marshall { northrup, overton }
+}
+
+import alder::*;
+
+fn main() {
+  let pettygrove: burnside = couch;
+  let quimby: everett = flanders;
+  let raleigh: irving = johnson;
+  let savier: marshall;
+}