Lower extern crates to imports

This is probably not completely correct, but it kind of works.

1 files changed, 16 insertions, 3 deletions

diff --git a/crates/ra_hir/src/nameres/lower.rs b/crates/ra_hir/src/nameres/lower.rs
index df87f520f..db898a782 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,
@@ -186,8 +186,21 @@ 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,
+                    });
+                }
             }
             ast::ModuleItemKind::ConstDef(it) => {
                 if let Some(name) = it.name() {