Merge #7541

7541: Use block_def_map in body lowering (third time's the charm) r=jonas-schievink a=jonas-schievink

After https://github.com/rust-analyzer/rust-analyzer/pull/7380 and https://github.com/rust-analyzer/rust-analyzer/pull/7506 both had to be reverted, this should have finally resolved all remaining bugs.

Most importantly, the optimization to skip `block_def_map` computation when the block contains no inner items was fixed (which fortunately was simpler than expected).

I've ran `analysis-stats` on libstd locally, which works fine, and also ran this PR locally for a short while without issues.

Note that this *still* has no (or almost no) user-facing impact, because the rest of r-a still relies on some local item support hacks.

bors r+

Co-authored-by: Jonas Schievink <[email protected]>

1 files changed, 9 insertions, 4 deletions

diff --git a/crates/hir_def/src/nameres.rs b/crates/hir_def/src/nameres.rs
index 0a15fc470..ece5958f4 100644
--- a/crates/hir_def/src/nameres.rs
+++ b/crates/hir_def/src/nameres.rs
@@ -197,12 +197,17 @@ impl DefMap {
         Arc::new(def_map)
     }
 
-    pub(crate) fn block_def_map_query(db: &dyn DefDatabase, block_id: BlockId) -> Arc<DefMap> {
+    pub(crate) fn block_def_map_query(
+        db: &dyn DefDatabase,
+        block_id: BlockId,
+    ) -> Option<Arc<DefMap>> {
         let block: BlockLoc = db.lookup_intern_block(block_id);
         let parent = block.module.def_map(db);
 
-        // FIXME: It would be good to just return the parent map when the block has no items, but
-        // we rely on `def_map.block` in a few places, which is `Some` for the inner `DefMap`.
+        let item_tree = db.item_tree(block.ast_id.file_id);
+        if item_tree.inner_items_of_block(block.ast_id.value).is_empty() {
+            return None;
+        }
 
         let block_info =
             BlockInfo { block: block_id, parent, parent_module: block.module.local_id };
@@ -211,7 +216,7 @@ impl DefMap {
         def_map.block = Some(block_info);
 
         let def_map = collector::collect_defs(db, def_map, Some(block.ast_id));
-        Arc::new(def_map)
+        Some(Arc::new(def_map))
     }
 
     fn empty(krate: CrateId, edition: Edition) -> DefMap {