Handle extern crates better, so they work correctly in 2015 edition

(see the removed comment.)

2 files changed, 38 insertions, 7 deletions

diff --git a/crates/ra_hir/src/nameres/lower.rs b/crates/ra_hir/src/nameres/lower.rs
index 922dbe9c1..81d80654c 100644
--- a/crates/ra_hir/src/nameres/lower.rs
+++ b/crates/ra_hir/src/nameres/lower.rs
@@ -8,7 +8,7 @@ use ra_arena::{Arena, RawId, impl_arena_id, map::ArenaMap};
 use rustc_hash::FxHashMap;
 
 use crate::{
-    SourceItemId, Path, PathKind, ModuleSource, Name,
+    SourceItemId, Path, ModuleSource, Name,
     HirFileId, MacroCallLoc, AsName, PerNs, Function,
     ModuleDef, Module, Struct, Enum, Const, Static, Trait, Type,
     ids::LocationCtx, PersistentHirDatabase,
@@ -180,13 +180,8 @@ impl LoweredModule {
                 self.add_use_item(source_map, it);
             }
             ast::ModuleItemKind::ExternCrateItem(it) => {
-                // Lower `extern crate x` to `use ::x`. This is kind of cheating
-                // and only works if we always interpret absolute paths in the
-                // 2018 style; otherwise `::x` could also refer to a module in
-                // the crate root.
                 if let Some(name_ref) = it.name_ref() {
-                    let mut path = Path::from_name_ref(name_ref);
-                    path.kind = PathKind::Abs;
+                    let path = Path::from_name_ref(name_ref);
                     let alias = it.alias().and_then(|a| a.name()).map(AsName::as_name);
                     self.imports.alloc(ImportData {
                         path,
diff --git a/crates/ra_hir/src/nameres/tests.rs b/crates/ra_hir/src/nameres/tests.rs
index e764e0855..6402c89c0 100644
--- a/crates/ra_hir/src/nameres/tests.rs
+++ b/crates/ra_hir/src/nameres/tests.rs
@@ -543,6 +543,42 @@ fn extern_crate_rename() {
 }
 
 #[test]
+fn extern_crate_rename_2015_edition() {
+    let mut db = MockDatabase::with_files(
+        "
+        //- /main.rs
+        extern crate alloc as alloc_crate;
+
+        mod alloc;
+        mod sync;
+
+        //- /sync.rs
+        use alloc_crate::Arc;
+
+        //- /lib.rs
+        struct Arc;
+        ",
+    );
+    db.set_crate_graph_from_fixture(crate_graph! {
+        "main": ("/main.rs", "2015", ["alloc"]),
+        "alloc": ("/lib.rs", []),
+    });
+    let sync_id = db.file_id_of("/sync.rs");
+
+    let module = crate::source_binder::module_from_file_id(&db, sync_id).unwrap();
+    let krate = module.krate(&db).unwrap();
+    let item_map = db.item_map(krate);
+
+    check_module_item_map(
+        &item_map,
+        module.module_id,
+        "
+        Arc: t v
+        ",
+    );
+}
+
+#[test]
 fn import_across_source_roots() {
     let mut db = MockDatabase::with_files(
         "