2 files changed, 62 insertions, 8 deletions

diff --git a/crates/ra_hir/src/nameres/lower.rs b/crates/ra_hir/src/nameres/lower.rs
index df87f520f..7e6e48ae0 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, ModuleSource, Name,
+    SourceItemId, Path, PathKind, ModuleSource, Name,
     HirFileId, MacroCallLoc, AsName, PerNs, Function,
     ModuleDef, Module, Struct, Enum, Const, Static, Trait, Type,
     ids::LocationCtx, PersistentHirDatabase,
@@ -23,6 +23,7 @@ pub(super) struct ImportData {
     pub(super) path: Path,
     pub(super) alias: Option<Name>,
     pub(super) is_glob: bool,
+    pub(super) is_extern_crate: bool,
 }
 
 /// A set of items and imports declared inside a module, without relation to
@@ -186,8 +187,22 @@ impl LoweredModule {
             ast::ModuleItemKind::UseItem(it) => {
                 self.add_use_item(source_map, it);
             }
-            ast::ModuleItemKind::ExternCrateItem(_) => {
-                // TODO
+            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 alias = it.alias().and_then(|a| a.name()).map(AsName::as_name);
+                    self.imports.alloc(ImportData {
+                        path,
+                        alias,
+                        is_glob: false,
+                        is_extern_crate: true,
+                    });
+                }
             }
             ast::ModuleItemKind::ConstDef(it) => {
                 if let Some(name) = it.name() {
@@ -215,6 +230,7 @@ impl LoweredModule {
                 path,
                 alias,
                 is_glob: segment.is_none(),
+                is_extern_crate: false,
             });
             if let Some(segment) = segment {
                 source_map.insert(import, segment)
diff --git a/crates/ra_hir/src/nameres/tests.rs b/crates/ra_hir/src/nameres/tests.rs
index 81c8a4f12..0654dbaa1 100644
--- a/crates/ra_hir/src/nameres/tests.rs
+++ b/crates/ra_hir/src/nameres/tests.rs
@@ -329,7 +329,49 @@ fn item_map_across_crates() {
         module.module_id,
         "
             Baz: t v
-            test_crate: t
+        ",
+    );
+}
+
+#[test]
+fn extern_crate_rename() {
+    let (mut db, sr) = 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;
+    ",
+    );
+    let main_id = sr.files[RelativePath::new("/main.rs")];
+    let sync_id = sr.files[RelativePath::new("/sync.rs")];
+    let lib_id = sr.files[RelativePath::new("/lib.rs")];
+
+    let mut crate_graph = CrateGraph::default();
+    let main_crate = crate_graph.add_crate_root(main_id);
+    let lib_crate = crate_graph.add_crate_root(lib_id);
+    crate_graph
+        .add_dep(main_crate, "alloc".into(), lib_crate)
+        .unwrap();
+
+    db.set_crate_graph(Arc::new(crate_graph));
+
+    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
         ",
     );
 }
@@ -361,8 +403,6 @@ fn import_across_source_roots() {
 
     let main_id = sr2.files[RelativePath::new("/main.rs")];
 
-    eprintln!("lib = {:?}, main = {:?}", lib_id, main_id);
-
     let mut crate_graph = CrateGraph::default();
     let main_crate = crate_graph.add_crate_root(main_id);
     let lib_crate = crate_graph.add_crate_root(lib_id);
@@ -381,7 +421,6 @@ fn import_across_source_roots() {
         module.module_id,
         "
             C: t v
-            test_crate: t
         ",
     );
 }
@@ -423,7 +462,6 @@ fn reexport_across_crates() {
         module.module_id,
         "
             Baz: t v
-            test_crate: t
         ",
     );
 }