Always create a root definition when creating a new Definitions object.

src/librustc_ast_lowering/lib.rs

@@ -210,7 +210,7 @@ pub trait Resolver {
 
     fn local_def_id(&self, node: NodeId) -> LocalDefId;
 
-    fn create_def_with_parent(
+    fn create_def(
         &mut self,
         parent: LocalDefId,
         node_id: ast::NodeId,
@@ -449,7 +449,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 match tree.kind {
                     UseTreeKind::Simple(_, id1, id2) => {
                         for &id in &[id1, id2] {
-                            self.lctx.resolver.create_def_with_parent(
+                            self.lctx.resolver.create_def(
                                 owner,
                                 id,
                                 DefPathData::Misc,
@@ -696,7 +696,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
             *local_id_counter += 1;
             let owner = this.resolver.opt_local_def_id(owner).expect(
-                "you forgot to call `create_def_with_parent` or are lowering node-IDs \
+                "you forgot to call `create_def` or are lowering node-IDs \
                  that do not belong to the current owner",
             );
 
@@ -824,7 +824,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         };
 
         // Add a definition for the in-band lifetime def.
-        self.resolver.create_def_with_parent(
+        self.resolver.create_def(
             parent_def_id,
             node_id,
             DefPathData::LifetimeNs(str_name),
@@ -1112,7 +1112,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
                     let impl_trait_node_id = self.resolver.next_node_id();
                     let parent_def_id = self.current_hir_id_owner.last().unwrap().0;
-                    self.resolver.create_def_with_parent(
+                    self.resolver.create_def(
                         parent_def_id,
                         impl_trait_node_id,
                         DefPathData::ImplTrait,
@@ -1178,7 +1178,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                             let node_id = self.resolver.next_node_id();
 
                             // Add a definition for the in-band const def.
-                            self.resolver.create_def_with_parent(
+                            self.resolver.create_def(
                                 parent_def_id,
                                 node_id,
                                 DefPathData::AnonConst,
@@ -1644,7 +1644,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     let def_node_id = self.context.resolver.next_node_id();
                     let hir_id =
                         self.context.lower_node_id_with_owner(def_node_id, self.opaque_ty_id);
-                    self.context.resolver.create_def_with_parent(
+                    self.context.resolver.create_def(
                         self.parent,
                         def_node_id,
                         DefPathData::LifetimeNs(name.ident().name),

src/librustc_hir/definitions.rs

@@ -71,9 +71,9 @@ impl DefPathTable {
 }
 
 /// The definition table containing node definitions.
-/// It holds the `DefPathTable` for local `DefId`s/`DefPath`s and it also stores a
+/// It holds the `DefPathTable` for `LocalDefId`s/`DefPath`s.
-/// mapping from `NodeId`s to local `DefId`s.
+/// It also stores mappings to convert `LocalDefId`s to/from `HirId`s.
-#[derive(Clone, Default)]
+#[derive(Clone)]
 pub struct Definitions {
     table: DefPathTable,
 
@@ -328,11 +328,7 @@ impl Definitions {
     }
 
     /// Adds a root definition (no parent) and a few other reserved definitions.
-    pub fn create_root_def(
+    pub fn new(crate_name: &str, crate_disambiguator: CrateDisambiguator) -> Definitions {
-        &mut self,
-        crate_name: &str,
-        crate_disambiguator: CrateDisambiguator,
-    ) -> LocalDefId {
         let key = DefKey {
             parent: None,
             disambiguated_data: DisambiguatedDefPathData {
@@ -344,24 +340,34 @@ impl Definitions {
         let parent_hash = DefKey::root_parent_stable_hash(crate_name, crate_disambiguator);
         let def_path_hash = key.compute_stable_hash(parent_hash);
 
-        // Create the definition.
+        // Create the root definition.
-        let root = LocalDefId { local_def_index: self.table.allocate(key, def_path_hash) };
+        let mut table = DefPathTable::default();
+        let root = LocalDefId { local_def_index: table.allocate(key, def_path_hash) };
         assert_eq!(root.local_def_index, CRATE_DEF_INDEX);
 
-        root
+        Definitions {
+            table,
+            def_id_to_hir_id: Default::default(),
+            hir_id_to_def_id: Default::default(),
+            expansions_that_defined: Default::default(),
+            next_disambiguator: Default::default(),
+            parent_modules_of_macro_defs: Default::default(),
+        }
+    }
+
+    /// Retrieves the root definition.
+    pub fn get_root_def(&self) -> LocalDefId {
+        LocalDefId { local_def_index: CRATE_DEF_INDEX }
     }
 
     /// Adds a definition with a parent definition.
-    pub fn create_def_with_parent(
+    pub fn create_def(
         &mut self,
         parent: LocalDefId,
         data: DefPathData,
         expn_id: ExpnId,
     ) -> LocalDefId {
-        debug!(
+        debug!("create_def(parent={:?}, data={:?}, expn_id={:?})", parent, data, expn_id);
-            "create_def_with_parent(parent={:?}, data={:?}, expn_id={:?})",
-            parent, data, expn_id
-        );
 
         // The root node must be created with `create_root_def()`.
         assert!(data != DefPathData::CrateRoot);
@@ -382,7 +388,7 @@ impl Definitions {
         let parent_hash = self.table.def_path_hash(parent.local_def_index);
         let def_path_hash = key.compute_stable_hash(parent_hash);
 
-        debug!("create_def_with_parent: after disambiguation, key = {:?}", key);
+        debug!("create_def: after disambiguation, key = {:?}", key);
 
         // Create the definition.
         let def_id = LocalDefId { local_def_index: self.table.allocate(key, def_path_hash) };

src/librustc_interface/passes.rs

@@ -734,7 +734,10 @@ pub fn create_global_ctxt<'tcx>(
     arena: &'tcx WorkerLocal<Arena<'tcx>>,
 ) -> QueryContext<'tcx> {
     let sess = &compiler.session();
-    let defs: &'tcx Definitions = arena.alloc(mem::take(&mut resolver_outputs.definitions));
+    let defs: &'tcx Definitions = arena.alloc(mem::replace(
+        &mut resolver_outputs.definitions,
+        Definitions::new(crate_name, sess.local_crate_disambiguator()),
+    ));
 
     let query_result_on_disk_cache = rustc_incremental::load_query_result_cache(sess);
 

src/librustc_resolve/def_collector.rs

@@ -32,7 +32,7 @@ impl<'a, 'b> DefCollector<'a, 'b> {
     fn create_def(&mut self, node_id: NodeId, data: DefPathData, span: Span) -> LocalDefId {
         let parent_def = self.parent_def;
         debug!("create_def(node_id={:?}, data={:?}, parent_def={:?})", node_id, data, parent_def);
-        self.resolver.create_def_with_parent(parent_def, node_id, data, self.expansion, span)
+        self.resolver.create_def(parent_def, node_id, data, self.expansion, span)
     }
 
     fn with_parent<F: FnOnce(&mut Self)>(&mut self, parent_def: LocalDefId, f: F) {

src/librustc_resolve/lib.rs

@@ -1126,7 +1126,7 @@ impl ResolverAstLowering for Resolver<'_> {
     }
 
     /// Adds a definition with a parent definition.
-    fn create_def_with_parent(
+    fn create_def(
         &mut self,
         parent: LocalDefId,
         node_id: ast::NodeId,
@@ -1142,7 +1142,7 @@ impl ResolverAstLowering for Resolver<'_> {
             self.definitions.def_key(self.node_id_to_def_id[&node_id]),
         );
 
-        let def_id = self.definitions.create_def_with_parent(parent, data, expn_id);
+        let def_id = self.definitions.create_def(parent, data, expn_id);
 
         assert_eq!(self.def_id_to_span.push(span), def_id);
 
@@ -1150,7 +1150,7 @@ impl ResolverAstLowering for Resolver<'_> {
         // anything in the AST, so they don't have a `NodeId`. For these cases
         // we don't need a mapping from `NodeId` to `LocalDefId`.
         if node_id != ast::DUMMY_NODE_ID {
-            debug!("create_def_with_parent: def_id_to_node_id[{:?}] <-> {:?}", def_id, node_id);
+            debug!("create_def: def_id_to_node_id[{:?}] <-> {:?}", def_id, node_id);
             self.node_id_to_def_id.insert(node_id, def_id);
         }
         assert_eq!(self.def_id_to_node_id.push(node_id), def_id);
@@ -1187,8 +1187,8 @@ impl<'a> Resolver<'a> {
         let mut module_map = FxHashMap::default();
         module_map.insert(LocalDefId { local_def_index: CRATE_DEF_INDEX }, graph_root);
 
-        let mut definitions = Definitions::default();
+        let definitions = Definitions::new(crate_name, session.local_crate_disambiguator());
-        let root = definitions.create_root_def(crate_name, session.local_crate_disambiguator());
+        let root = definitions.get_root_def();
 
         let mut def_id_to_span = IndexVec::default();
         assert_eq!(def_id_to_span.push(rustc_span::DUMMY_SP), root);