One last refactoring of the import handling:

* Create an import resolving stage. Currently this involves a copy of the ast,
  we can probably revisit this once we revisit doing full copies of the ast in
  general.

* Don't repeat work. Once we resolve a import, put it on a hash table and use
  it next time we are asked for it. This solves a O(n^2) behaviour in
  degenerated cases.

* Once import resolution is done, the target of an import is stored on the
  import itself.

1 files changed, 8 insertions, 6 deletions

diff --git a/src/comp/middle/fold.rs b/src/comp/middle/fold.rs
index b96ca938..f81b7a52 100644
--- a/src/comp/middle/fold.rs
+++ b/src/comp/middle/fold.rs
@@ -210,7 +210,7 @@ type ast_fold[ENV] =
          def_id id) -> @view_item)                fold_view_item_use,
 
      (fn(&ENV e, &span sp, vec[ident] idents,
-         def_id id) -> @view_item)                fold_view_item_import,
+         def_id id, option.t[def]) -> @view_item) fold_view_item_import,
 
      // Additional nodes.
      (fn(&ENV e, &span sp,
@@ -705,9 +705,10 @@ fn fold_view_item[ENV](&ENV env, ast_fold[ENV] fld, @view_item vi)
             ret fld.fold_view_item_use(env_, vi.span, ident, meta_items,
                                        def_id);
         }
-        case (ast.view_item_import(?idents, ?def_id)) {
+        case (ast.view_item_import(?idents, ?def_id, ?target_def)) {
             // FIXME: what other folding should be done in here?
-            ret fld.fold_view_item_import(env_, vi.span, idents, def_id);
+            ret fld.fold_view_item_import(env_, vi.span, idents, def_id,
+                                          target_def);
         }
     }
 
@@ -1086,8 +1087,9 @@ fn identity_fold_view_item_use[ENV](&ENV e, &span sp, ident i,
 }
 
 fn identity_fold_view_item_import[ENV](&ENV e, &span sp, vec[ident] is,
-                                       def_id id) -> @view_item {
-    ret @respan(sp, ast.view_item_import(is, id));
+                                       def_id id, option.t[def] target_def)
+    -> @view_item {
+    ret @respan(sp, ast.view_item_import(is, id, target_def));
 }
 
 // Additional identities.
@@ -1236,7 +1238,7 @@ fn new_identity_fold[ENV]() -> ast_fold[ENV] {
          fold_view_item_use =
              bind identity_fold_view_item_use[ENV](_,_,_,_,_),
          fold_view_item_import =
-             bind identity_fold_view_item_import[ENV](_,_,_,_),
+             bind identity_fold_view_item_import[ENV](_,_,_,_,_),
 
          fold_block = bind identity_fold_block[ENV](_,_,_),
          fold_fn = bind identity_fold_fn[ENV](_,_,_,_,_),