Catch cyclic imports harder. Add 2 tests to confirm.

src/boot/me/semant.ml

@@ -1545,10 +1545,18 @@ let rec project_ident_from_items
     (cx:ctxt)
     (lchk:loop_check)
     (scopes:scope list)
+    (scope_id:node_id)
     ((view:Ast.mod_view),(items:Ast.mod_items))
     (ident:Ast.ident)
     (inside:bool)
     : resolved =
+
+  let lchk =
+    if List.mem (scope_id, ident) lchk
+    then err (Some scope_id) "cyclic import for ident %s" ident
+    else (scope_id, ident)::lchk
+  in
+
   if not (inside || (exports_permit view ident))
   then None
   else
@@ -1558,7 +1566,8 @@ let rec project_ident_from_items
       | None ->
           match htab_search view.Ast.view_imports ident with
               None -> None
-            | Some name -> lookup_by_name cx lchk scopes name
+            | Some name ->
+                lookup_by_name cx lchk scopes name
 
 and found cx scopes id =
   Hashtbl.replace cx.ctxt_node_referenced id ();
@@ -1578,7 +1587,7 @@ and project_name_comp_from_resolved
         let ident = get_name_comp_ident ext in
         let md = get_mod_item cx id in
           Hashtbl.replace cx.ctxt_node_referenced id ();
-          project_ident_from_items cx lchk scopes md ident false
+          project_ident_from_items cx lchk scopes id md ident false
 
 and lookup_by_name
     (cx:ctxt)
@@ -1602,12 +1611,6 @@ and lookup_by_ident
     (ident:Ast.ident)
     : resolved =
 
-  let passing id =
-    if List.mem (id, ident) lchk
-    then err (Some id) "cyclic import for ident %s" ident
-    else (id, ident)::lchk
-  in
-
   let check_slots scopes islots =
     arr_search islots
       (fun _ (sloti,ident') ->
@@ -1651,7 +1654,7 @@ and lookup_by_ident
 
       | SCOPE_crate crate ->
           project_ident_from_items
-            cx (passing crate.id) scopes crate.node.Ast.crate_items ident true
+            cx lchk scopes crate.id crate.node.Ast.crate_items ident true
 
       | SCOPE_obj_fn fn ->
           would_capture (check_slots scopes fn.node.Ast.fn_input_slots)
@@ -1671,8 +1674,8 @@ and lookup_by_ident
                     end
 
                 | Ast.MOD_ITEM_mod md ->
-                    project_ident_from_items cx (passing item.id)
-                      scopes md ident true
+                    project_ident_from_items cx lchk
+                      scopes item.id md ident true
 
                 | _ -> None
             in

src/test/compile-fail/import-loop-2.rs

@@ -0,0 +1,13 @@
+// error-pattern:cyclic import
+
+mod a {
+  import b.x;
+}
+
+mod b {
+  import a.x;
+
+  fn main() {
+    auto y = x;
+  }
+}

src/test/compile-fail/import-loop.rs

@@ -0,0 +1,7 @@
+// error-pattern:cyclic import
+
+import x;
+
+fn main() {
+  auto y = x;
+}