Remove mutability in ResolverAstLowering.

Author: cjgillot

compiler/rustc_ast_lowering/src/lib.rs

@@ -162,7 +162,7 @@ struct LoweringContext<'a, 'hir: 'a> {
 }
 
 pub trait ResolverAstLowering {
-    fn def_key(&mut self, id: DefId) -> DefKey;
+    fn def_key(&self, id: DefId) -> DefKey;
 
     fn def_span(&self, id: LocalDefId) -> Span;
 
@@ -174,17 +174,17 @@ pub trait ResolverAstLowering {
     fn get_partial_res(&self, id: NodeId) -> Option<PartialRes>;
 
     /// Obtains per-namespace resolutions for `use` statement with the given `NodeId`.
-    fn get_import_res(&mut self, id: NodeId) -> PerNS<Option<Res<NodeId>>>;
+    fn get_import_res(&self, id: NodeId) -> PerNS<Option<Res<NodeId>>>;
 
     /// Obtains resolution for a label with the given `NodeId`.
-    fn get_label_res(&mut self, id: NodeId) -> Option<NodeId>;
-
-    /// We must keep the set of definitions up to date as we add nodes that weren't in the AST.
-    /// This should only return `None` during testing.
-    fn definitions(&mut self) -> &mut Definitions;
+    fn get_label_res(&self, id: NodeId) -> Option<NodeId>;
 
     fn create_stable_hashing_context(&self) -> StableHashingContext<'_>;
 
+    fn definitions(&self) -> &Definitions;
+
+    fn init_def_id_to_hir_id_mapping(&mut self, mapping: IndexVec<LocalDefId, Option<hir::HirId>>);
+
     fn lint_buffer(&mut self) -> &mut LintBuffer;
 
     fn next_node_id(&mut self) -> NodeId;
@@ -412,7 +412,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             }
         }
 
-        self.resolver.definitions().init_def_id_to_hir_id_mapping(def_id_to_hir_id);
+        self.resolver.init_def_id_to_hir_id_mapping(def_id_to_hir_id);
 
         let krate = hir::Crate { owners: self.owners, hir_hash };
         self.arena.alloc(krate)

compiler/rustc_resolve/src/lib.rs

@@ -1134,9 +1134,9 @@ impl<'a, 'b> DefIdTree for &'a Resolver<'b> {
 /// This interface is used through the AST→HIR step, to embed full paths into the HIR. After that
 /// the resolver is no longer needed as all the relevant information is inline.
 impl ResolverAstLowering for Resolver<'_> {
-    fn def_key(&mut self, id: DefId) -> DefKey {
+    fn def_key(&self, id: DefId) -> DefKey {
         if let Some(id) = id.as_local() {
-            self.definitions().def_key(id)
+            self.definitions.def_key(id)
         } else {
             self.cstore().def_key(id)
         }
@@ -1163,22 +1163,29 @@ impl ResolverAstLowering for Resolver<'_> {
         self.partial_res_map.get(&id).cloned()
     }
 
-    fn get_import_res(&mut self, id: NodeId) -> PerNS<Option<Res>> {
+    fn get_import_res(&self, id: NodeId) -> PerNS<Option<Res>> {
         self.import_res_map.get(&id).cloned().unwrap_or_default()
     }
 
-    fn get_label_res(&mut self, id: NodeId) -> Option<NodeId> {
+    fn get_label_res(&self, id: NodeId) -> Option<NodeId> {
         self.label_res_map.get(&id).cloned()
     }
 
-    fn definitions(&mut self) -> &mut Definitions {
-        &mut self.definitions
-    }
-
     fn create_stable_hashing_context(&self) -> StableHashingContext<'_> {
         StableHashingContext::new(self.session, &self.definitions, self.crate_loader.cstore())
     }
 
+    fn definitions(&self) -> &Definitions {
+        &self.definitions
+    }
+
+    fn init_def_id_to_hir_id_mapping(
+        &mut self,
+        mapping: IndexVec<LocalDefId, Option<rustc_hir::HirId>>,
+    ) {
+        self.definitions.init_def_id_to_hir_id_mapping(mapping)
+    }
+
     fn lint_buffer(&mut self) -> &mut LintBuffer {
         &mut self.lint_buffer
     }