Don't re-export a glob-imported ID when the same ID is defined within

a module

See the test case I added (issue-2316-c) for a concrete example.
issue-2316 also contains the originally reported test case. resolve
was using bitwise or instead of logical or when checking exports,
resulting in excessively eager evaluation. A one-line fix that took
six hours to isolate ;-)

src/rustc/metadata/csearch.rs

@@ -70,7 +70,7 @@ fn resolve_path(cstore: cstore::cstore, cnum: ast::crate_num,
             result += [(cnum, cm.data, def)];
         } else {
             if cm.cnum_map.contains_key(def.crate) {
-                // This reexport is itself a reexport from anther crate
+                // This reexport is itself a reexport from another crate
                 let next_cnum = cm.cnum_map.get(def.crate);
                 let next_cm_data = cstore::get_crate_data(cstore, next_cnum);
                 result += [(next_cnum, next_cm_data.data, def)];

src/rustc/middle/resolve.rs

@@ -1667,9 +1667,12 @@ fn ns_for_def(d: def) -> namespace {
 fn lookup_external(e: env, cnum: int, ids: [ident], ns: namespace) ->
    option<def> {
     let mut result = none;
+    let mut done = false;
     for csearch::lookup_defs(e.sess.cstore, cnum, ids).each {|d|
         e.ext_map.insert(def_id_of_def(d), ids);
-        if ns == ns_for_def(d) { result = some(d); }
+        if ns == ns_for_def(d) && !done {
+                result = some(d);
+         }
     }
     ret result;
 }
@@ -1998,8 +2001,14 @@ fn check_exports(e: @env) {
                 }
             }
         }
-        found_something |= lookup_glob_any(e, _mod, vi.span, ident,
-                                           export_id);
+        /*
+          This code previously used bitwise or (|=) but that was wrong,
+          because we need or to be lazy here. If something was already
+          found, we don't want to call lookup_glob_any (see #2316 for
+          what happens if we do)
+         */
+        found_something = found_something ||
+           lookup_glob_any(e, _mod, vi.span, ident, export_id);
         if !found_something {
             e.sess.span_warn(vi.span,
                              #fmt("exported item %s is not defined", ident));