Add sufficient import support to compile some simple single-crate programs.

This is likely not the final solution. It does repetitive work and doesn't produce
errors for invalid but unused imports. In any case, I think it is a useful step.

3 files changed, 115 insertions, 37 deletions

diff --git a/src/comp/front/ast.rs b/src/comp/front/ast.rs
index fff7b24c..5dc0c4d2 100644
--- a/src/comp/front/ast.rs
+++ b/src/comp/front/ast.rs
@@ -36,7 +36,6 @@ tag def {
     def_ty_arg(def_id);
     def_binding(def_id);
     def_use(def_id);
-    def_import(def_id);
 }
 
 type crate = spanned[crate_];
diff --git a/src/comp/middle/fold.rs b/src/comp/middle/fold.rs
index 70f6e470..6679fc5f 100644
--- a/src/comp/middle/fold.rs
+++ b/src/comp/middle/fold.rs
@@ -781,14 +781,14 @@ fn fold_mod[ENV](&ENV e, ast_fold[ENV] fld, &ast._mod m) -> ast._mod {
     let vec[@item] items = vec();
     auto index = m.index;
 
-    for (@item i in m.items) {
-        append[@item](items, fold_item[ENV](e, fld, i));
-    }
-
     for (@view_item vi in m.view_items) {
         append[@view_item](view_items, fold_view_item[ENV](e, fld, vi));
     }
 
+    for (@item i in m.items) {
+        append[@item](items, fold_item[ENV](e, fld, i));
+    }
+
     ret fld.fold_mod(e, rec(view_items=view_items, items=items, index=index));
  }
 
diff --git a/src/comp/middle/resolve.rs b/src/comp/middle/resolve.rs
index e1f58b5d..808637e7 100644
--- a/src/comp/middle/resolve.rs
+++ b/src/comp/middle/resolve.rs
@@ -24,39 +24,106 @@ tag scope {
 type env = rec(list[scope] scopes,
                session.session sess);
 
-fn lookup_name(&env e, ast.ident i) -> option.t[def] {
+// A simple wrapper over defs that stores a bit more information about modules
+// and uses so that we can use the regular lookup_name when resolving imports.
+tag def_wrap {
+    def_wrap_use(@ast.view_item);
+    def_wrap_mod(@ast.item);
+    def_wrap_other(def);
+}
+
+fn unwrap_def(option.t[def_wrap] d_) -> option.t[def] {
+    alt (d_) {
+        case (none[def_wrap]) {
+            ret none[def];
+        }
+        case (some[def_wrap](?d)) {
+            alt (d) {
+                case (def_wrap_use(?it)) {
+                    alt (it.node) {
+                        case (ast.view_item_use(_, _, ?id)) {
+                            ret some[def](ast.def_use(id));
+                        }
+                    }
+                    fail;
+                }
+                case (def_wrap_mod(?i)) {
+                    alt (i.node) {
+                        case (ast.item_mod(_, _, ?id)) {
+                            ret some[def](ast.def_mod(id));
+                        }
+                    }
+                    fail;
+                }
+                case (def_wrap_other(?d)) {
+                    ret some[def](d);
+                }
+            }
+        }
+    }
+    fail;
+}
+
+// Follow the path of an import and return what it ultimately points to.
+
+fn find_final_def(&env e, vec[ident] idents) -> option.t[def_wrap] {
+    auto len = _vec.len[ident](idents);
+    auto first = idents.(0);
+    if (len == 1u) {
+        ret lookup_name(e, first);
+    }
+    auto d_ = lookup_name(e, first);
+    alt (d_) {
+        case (none[def_wrap]) {
+            ret d_;
+        }
+        case (some[def_wrap](?d)) {
+            alt(d) {
+                case (def_wrap_mod(?i)) {
+                    auto new_env = update_env_for_item(e, i);
+                    auto new_idents = _vec.slice[ident](idents, 1u, len);
+                    ret find_final_def(new_env, new_idents);
+                }
+            }
+        }
+    }
+    fail;
+}
+
+fn lookup_name(&env e, ast.ident i) -> option.t[def_wrap] {
 
     // log "resolving name " + i;
 
-    fn found_def_item(@ast.item i) -> option.t[def] {
+    fn found_def_item(@ast.item i) -> option.t[def_wrap] {
         alt (i.node) {
             case (ast.item_const(_, _, _, ?id, _)) {
-                ret some[def](ast.def_const(id));
+                ret some[def_wrap](def_wrap_other(ast.def_const(id)));
             }
             case (ast.item_fn(_, _, _, ?id, _)) {
-                ret some[def](ast.def_fn(id));
+                ret some[def_wrap](def_wrap_other(ast.def_fn(id)));
             }
             case (ast.item_mod(_, _, ?id)) {
-                ret some[def](ast.def_mod(id));
+                ret some[def_wrap](def_wrap_mod(i));
             }
             case (ast.item_ty(_, _, _, ?id, _)) {
-                ret some[def](ast.def_ty(id));
+                ret some[def_wrap](def_wrap_other(ast.def_ty(id)));
             }
             case (ast.item_tag(_, _, _, ?id)) {
-                ret some[def](ast.def_ty(id));
+                ret some[def_wrap](def_wrap_other(ast.def_ty(id)));
             }
             case (ast.item_obj(_, _, _, ?id, _)) {
-                ret some[def](ast.def_obj(id));
+                ret some[def_wrap](def_wrap_other(ast.def_obj(id)));
             }
         }
     }
 
-    fn found_decl_stmt(@ast.stmt s) -> option.t[def] {
+    fn found_decl_stmt(@ast.stmt s) -> option.t[def_wrap] {
         alt (s.node) {
             case (ast.stmt_decl(?d)) {
                 alt (d.node) {
                     case (ast.decl_local(?loc)) {
-                        ret some[def](ast.def_local(loc.id));
+                        auto t = ast.def_local(loc.id);
+                        ret some[def_wrap](def_wrap_other(t));
                     }
                     case (ast.decl_item(?it)) {
                         ret found_def_item(it);
@@ -64,26 +131,32 @@ fn lookup_name(&env e, ast.ident i) -> option.t[def] {
                 }
             }
         }
-        ret none[def];
+        ret none[def_wrap];
     }
 
-    fn found_def_view(@ast.view_item i) -> option.t[def] {
+    fn found_def_view(&env e, @ast.view_item i) -> option.t[def_wrap] {
         alt (i.node) {
             case (ast.view_item_use(_, _, ?id)) {
-                ret some[def](ast.def_use(id));
+                ret some[def_wrap](def_wrap_use(i));
             }
-            case (ast.view_item_import(_,?id)) {
-                ret some[def](ast.def_import(id));
+            case (ast.view_item_import(?idents,_)) {
+                auto d = find_final_def(e, idents);
+                alt (d) {
+                    case (some[def_wrap](_)) {
+                        ret d;
+                    }
+                }
             }
         }
+        fail;
     }
 
-    fn check_mod(ast.ident i, ast._mod m) -> option.t[def] {
+    fn check_mod(&env e, ast.ident i, ast._mod m) -> option.t[def_wrap] {
         alt (m.index.find(i)) {
             case (some[ast.mod_index_entry](?ent)) {
                 alt (ent) {
                     case (ast.mie_view_item(?ix)) {
-                        ret found_def_view(m.view_items.(ix));
+                        ret found_def_view(e, m.view_items.(ix));
                     }
                     case (ast.mie_item(?ix)) {
                         ret found_def_item(m.items.(ix));
@@ -92,7 +165,8 @@ fn lookup_name(&env e, ast.ident i) -> option.t[def] {
                         alt (m.items.(item_idx).node) {
                             case (ast.item_tag(_, ?variants, _, ?tid)) {
                                 auto vid = variants.(variant_idx).id;
-                                ret some[def](ast.def_variant(tid, vid));
+                                auto t = ast.def_variant(tid, vid);
+                                ret some[def_wrap](def_wrap_other(t));
                             }
                             case (_) {
                                 log "tag item not actually a tag";
@@ -104,15 +178,15 @@ fn lookup_name(&env e, ast.ident i) -> option.t[def] {
             }
             case (none[ast.mod_index_entry]) { /* fall through */ }
         }
-        ret none[def];
+        ret none[def_wrap];
     }
 
 
-    fn in_scope(ast.ident i, &scope s) -> option.t[def] {
+    fn in_scope(ast.ident i, env e, &scope s) -> option.t[def_wrap] {
         alt (s) {
 
             case (scope_crate(?c)) {
-                ret check_mod(i, c.node.module);
+                ret check_mod(e, i, c.node.module);
             }
 
             case (scope_item(?it)) {
@@ -120,29 +194,33 @@ fn lookup_name(&env e, ast.ident i) -> option.t[def] {
                     case (ast.item_fn(_, ?f, ?ty_params, _, _)) {
                         for (ast.arg a in f.inputs) {
                             if (_str.eq(a.ident, i)) {
-                                ret some[def](ast.def_arg(a.id));
+                                auto t = ast.def_arg(a.id);
+                                ret some[def_wrap](def_wrap_other(t));
                             }
                         }
                         for (ast.ty_param tp in ty_params) {
                             if (_str.eq(tp.ident, i)) {
-                                ret some[def](ast.def_ty_arg(tp.id));
+                                auto t = ast.def_ty_arg(tp.id);
+                                ret some[def_wrap](def_wrap_other(t));
                             }
                         }
                     }
                     case (ast.item_obj(_, ?ob, ?ty_params, _, _)) {
                         for (ast.obj_field f in ob.fields) {
                             if (_str.eq(f.ident, i)) {
-                                ret some[def](ast.def_obj_field(f.id));
+                                auto t = ast.def_obj_field(f.id);
+                                ret some[def_wrap](def_wrap_other(t));
                             }
                         }
                         for (ast.ty_param tp in ty_params) {
                             if (_str.eq(tp.ident, i)) {
-                                ret some[def](ast.def_ty_arg(tp.id));
+                                auto t = ast.def_ty_arg(tp.id);
+                                ret some[def_wrap](def_wrap_other(t));
                             }
                         }
                     }
                     case (ast.item_mod(_, ?m, _)) {
-                        ret check_mod(i, m);
+                        ret check_mod(e, i, m);
                     }
                     case (_) { /* fall through */ }
                 }
@@ -160,22 +238,23 @@ fn lookup_name(&env e, ast.ident i) -> option.t[def] {
             case (scope_arm(?a)) {
                 alt (a.index.find(i)) {
                     case (some[ast.def_id](?did)) {
-                        ret some[def](ast.def_binding(did));
+                        auto t = ast.def_binding(did);
+                        ret some[def_wrap](def_wrap_other(t));
                     }
                     case (_) { /* fall through */  }
                 }
             }
         }
-        ret none[def];
+        ret none[def_wrap];
     }
 
-    ret std.list.find[scope,def](e.scopes, bind in_scope(i, _));
+    ret std.list.find[scope,def_wrap](e.scopes, bind in_scope(i, e, _));
 }
 
 fn fold_pat_tag(&env e, &span sp, ident i, vec[@ast.pat] args,
                 option.t[ast.variant_def] old_def, ann a) -> @ast.pat {
     auto new_def;
-    alt (lookup_name(e, i)) {
+    alt (unwrap_def(lookup_name(e, i))) {
         case (some[def](?d)) {
             alt (d) {
                 case (ast.def_variant(?did, ?vid)) {
@@ -203,7 +282,7 @@ fn fold_expr_name(&env e, &span sp, &ast.name n,
         e.sess.unimpl("resolving name expr with ty params");
     }
 
-    auto d_ = lookup_name(e, n.node.ident);
+    auto d_ = unwrap_def(lookup_name(e, n.node.ident));
 
     alt (d_) {
         case (some[def](_)) {
@@ -232,7 +311,7 @@ fn fold_ty_path(&env e, &span sp, ast.path p,
         e.sess.unimpl("resolving path ty with ty params");
     }
 
-    auto d_ = lookup_name(e, n.node.ident);
+    auto d_ = unwrap_def(lookup_name(e, n.node.ident));
 
     alt (d_) {
         case (some[def](_)) {