Merge #8997

8997: internal: stop expanding UseTrees during ItemTree lowering r=jonas-schievink a=jonas-schievink

Closes https://github.com/rust-analyzer/rust-analyzer/issues/8908

Messy diff, but `ItemTree` lowering got simpler, since we now have a strict 1-to-1 mapping between `ast::Item` and `ModItem`.

The most messy part is mapping a single `UseTree` back to its `ast::UseTree` counterpart for diagnostics, but I think the ad-hoc source map built during lowering does the job.

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

1 files changed, 6 insertions, 20 deletions

diff --git a/crates/hir/src/lib.rs b/crates/hir/src/lib.rs
index 1ecd2391b..01b2de515 100644
--- a/crates/hir/src/lib.rs
+++ b/crates/hir/src/lib.rs
@@ -472,27 +472,13 @@ impl Module {
                     });
                 }
 
-                DefDiagnosticKind::UnresolvedImport { ast, index } => {
-                    let use_item = ast.to_node(db.upcast());
-                    let hygiene = Hygiene::new(db.upcast(), ast.file_id);
-                    let mut cur = 0;
-                    let mut tree = None;
-                    ModPath::expand_use_item(
-                        db.upcast(),
-                        InFile::new(ast.file_id, use_item),
-                        &hygiene,
-                        |_mod_path, use_tree, _is_glob, _alias| {
-                            if cur == *index {
-                                tree = Some(use_tree.clone());
-                            }
-
-                            cur += 1;
-                        },
-                    );
+                DefDiagnosticKind::UnresolvedImport { id, index } => {
+                    let file_id = id.file_id();
+                    let item_tree = id.item_tree(db.upcast());
+                    let import = &item_tree[id.value];
 
-                    if let Some(tree) = tree {
-                        sink.push(UnresolvedImport { file: ast.file_id, node: AstPtr::new(&tree) });
-                    }
+                    let use_tree = import.use_tree_to_ast(db.upcast(), file_id, *index);
+                    sink.push(UnresolvedImport { file: file_id, node: AstPtr::new(&use_tree) });
                 }
 
                 DefDiagnosticKind::UnconfiguredCode { ast, cfg, opts } => {