Rollup merge of #143550 - petrochenkov:lessmutres, r=lcnr

resolve: Use interior mutability for extern module map

Module map for extern modules is a lazily populated cache, it's not *significantly* mutable.
If some logic in name resolver is parallelized, then this cache can be populated from any thread, and without affecting results of any speculative resolution.

Unblocks https://github.com/rust-lang/rust/pull/143884.
This is a part of [#gsoc > Project: Parallel Macro Expansion](https://rust-lang.zulipchat.com/#narrow/channel/421156-gsoc/topic/Project.3A.20Parallel.20Macro.20Expansion/with/527348747).
cc `@LorrensP-2158466`

1 files changed, 45 insertions, 38 deletions

diff --git a/compiler/rustc_resolve/src/lib.rs b/compiler/rustc_resolve/src/lib.rs
index f904f326296..dae30b77ec1 100644
--- a/compiler/rustc_resolve/src/lib.rs
+++ b/compiler/rustc_resolve/src/lib.rs
@@ -585,6 +585,10 @@ struct ModuleData<'ra> {
     span: Span,
 
     expansion: ExpnId,
+
+    /// Binding for implicitly declared names that come with a module,
+    /// like `self` (not yet used), or `crate`/`$crate` (for root modules).
+    self_binding: Option<NameBinding<'ra>>,
 }
 
 /// All modules are unique and allocated on a same arena,
@@ -613,6 +617,7 @@ impl<'ra> ModuleData<'ra> {
         expansion: ExpnId,
         span: Span,
         no_implicit_prelude: bool,
+        self_binding: Option<NameBinding<'ra>>,
     ) -> Self {
         let is_foreign = match kind {
             ModuleKind::Def(_, def_id, _) => !def_id.is_local(),
@@ -630,6 +635,7 @@ impl<'ra> ModuleData<'ra> {
             traits: RefCell::new(None),
             span,
             expansion,
+            self_binding,
         }
     }
 }
@@ -1075,7 +1081,10 @@ pub struct Resolver<'ra, 'tcx> {
     /// some AST passes can generate identifiers that only resolve to local or
     /// lang items.
     empty_module: Module<'ra>,
-    module_map: FxIndexMap<DefId, Module<'ra>>,
+    /// Eagerly populated map of all local non-block modules.
+    local_module_map: FxIndexMap<LocalDefId, Module<'ra>>,
+    /// Lazily populated cache of modules loaded from external crates.
+    extern_module_map: RefCell<FxIndexMap<DefId, Module<'ra>>>,
     binding_parent_modules: FxHashMap<NameBinding<'ra>, Module<'ra>>,
 
     underscore_disambiguator: u32,
@@ -1101,17 +1110,14 @@ pub struct Resolver<'ra, 'tcx> {
     builtin_types_bindings: FxHashMap<Symbol, NameBinding<'ra>>,
     builtin_attrs_bindings: FxHashMap<Symbol, NameBinding<'ra>>,
     registered_tool_bindings: FxHashMap<Ident, NameBinding<'ra>>,
-    /// Binding for implicitly declared names that come with a module,
-    /// like `self` (not yet used), or `crate`/`$crate` (for root modules).
-    module_self_bindings: FxHashMap<Module<'ra>, NameBinding<'ra>>,
-
     used_extern_options: FxHashSet<Symbol>,
     macro_names: FxHashSet<Ident>,
     builtin_macros: FxHashMap<Symbol, SyntaxExtensionKind>,
     registered_tools: &'tcx RegisteredTools,
     macro_use_prelude: FxIndexMap<Symbol, NameBinding<'ra>>,
+    /// Eagerly populated map of all local macro definitions.
     local_macro_map: FxHashMap<LocalDefId, &'ra MacroData>,
-    /// Lazily populated cache of macros loaded from external crates.
+    /// Lazily populated cache of macro definitions loaded from external crates.
     extern_macro_map: RefCell<FxHashMap<DefId, &'ra MacroData>>,
     dummy_ext_bang: Arc<SyntaxExtension>,
     dummy_ext_derive: Arc<SyntaxExtension>,
@@ -1263,26 +1269,25 @@ impl<'ra> ResolverArenas<'ra> {
         expn_id: ExpnId,
         span: Span,
         no_implicit_prelude: bool,
-        module_map: &mut FxIndexMap<DefId, Module<'ra>>,
-        module_self_bindings: &mut FxHashMap<Module<'ra>, NameBinding<'ra>>,
     ) -> Module<'ra> {
+        let (def_id, self_binding) = match kind {
+            ModuleKind::Def(def_kind, def_id, _) => (
+                Some(def_id),
+                Some(self.new_pub_res_binding(Res::Def(def_kind, def_id), span, LocalExpnId::ROOT)),
+            ),
+            ModuleKind::Block => (None, None),
+        };
         let module = Module(Interned::new_unchecked(self.modules.alloc(ModuleData::new(
             parent,
             kind,
             expn_id,
             span,
             no_implicit_prelude,
+            self_binding,
         ))));
-        let def_id = module.opt_def_id();
         if def_id.is_none_or(|def_id| def_id.is_local()) {
             self.local_modules.borrow_mut().push(module);
         }
-        if let Some(def_id) = def_id {
-            module_map.insert(def_id, module);
-            let res = module.res().unwrap();
-            let binding = self.new_pub_res_binding(res, module.span, LocalExpnId::ROOT);
-            module_self_bindings.insert(module, binding);
-        }
         module
     }
     fn local_modules(&'ra self) -> std::cell::Ref<'ra, Vec<Module<'ra>>> {
@@ -1423,25 +1428,21 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         arenas: &'ra ResolverArenas<'ra>,
     ) -> Resolver<'ra, 'tcx> {
         let root_def_id = CRATE_DEF_ID.to_def_id();
-        let mut module_map = FxIndexMap::default();
-        let mut module_self_bindings = FxHashMap::default();
+        let mut local_module_map = FxIndexMap::default();
         let graph_root = arenas.new_module(
             None,
             ModuleKind::Def(DefKind::Mod, root_def_id, None),
             ExpnId::root(),
             crate_span,
             attr::contains_name(attrs, sym::no_implicit_prelude),
-            &mut module_map,
-            &mut module_self_bindings,
         );
+        local_module_map.insert(CRATE_DEF_ID, graph_root);
         let empty_module = arenas.new_module(
             None,
             ModuleKind::Def(DefKind::Mod, root_def_id, None),
             ExpnId::root(),
             DUMMY_SP,
             true,
-            &mut Default::default(),
-            &mut Default::default(),
         );
 
         let mut node_id_to_def_id = NodeMap::default();
@@ -1502,7 +1503,8 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             trait_map: NodeMap::default(),
             underscore_disambiguator: 0,
             empty_module,
-            module_map,
+            local_module_map,
+            extern_module_map: Default::default(),
             block_map: Default::default(),
             binding_parent_modules: FxHashMap::default(),
             ast_transform_scopes: FxHashMap::default(),
@@ -1544,8 +1546,6 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     (*ident, binding)
                 })
                 .collect(),
-            module_self_bindings,
-
             used_extern_options: Default::default(),
             macro_names: FxHashSet::default(),
             builtin_macros: Default::default(),
@@ -1608,7 +1608,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         resolver
     }
 
-    fn new_module(
+    fn new_local_module(
         &mut self,
         parent: Option<Module<'ra>>,
         kind: ModuleKind,
@@ -1616,17 +1616,24 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         span: Span,
         no_implicit_prelude: bool,
     ) -> Module<'ra> {
-        let module_map = &mut self.module_map;
-        let module_self_bindings = &mut self.module_self_bindings;
-        self.arenas.new_module(
-            parent,
-            kind,
-            expn_id,
-            span,
-            no_implicit_prelude,
-            module_map,
-            module_self_bindings,
-        )
+        let module = self.arenas.new_module(parent, kind, expn_id, span, no_implicit_prelude);
+        if let Some(def_id) = module.opt_def_id() {
+            self.local_module_map.insert(def_id.expect_local(), module);
+        }
+        module
+    }
+
+    fn new_extern_module(
+        &self,
+        parent: Option<Module<'ra>>,
+        kind: ModuleKind,
+        expn_id: ExpnId,
+        span: Span,
+        no_implicit_prelude: bool,
+    ) -> Module<'ra> {
+        let module = self.arenas.new_module(parent, kind, expn_id, span, no_implicit_prelude);
+        self.extern_module_map.borrow_mut().insert(module.def_id(), module);
+        module
     }
 
     fn new_local_macro(&mut self, def_id: LocalDefId, macro_data: MacroData) -> &'ra MacroData {
@@ -2012,7 +2019,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         }
     }
 
-    fn resolve_crate_root(&mut self, ident: Ident) -> Module<'ra> {
+    fn resolve_crate_root(&self, ident: Ident) -> Module<'ra> {
         debug!("resolve_crate_root({:?})", ident);
         let mut ctxt = ident.span.ctxt();
         let mark = if ident.name == kw::DollarCrate {
@@ -2085,7 +2092,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         module
     }
 
-    fn resolve_self(&mut self, ctxt: &mut SyntaxContext, module: Module<'ra>) -> Module<'ra> {
+    fn resolve_self(&self, ctxt: &mut SyntaxContext, module: Module<'ra>) -> Module<'ra> {
         let mut module = self.expect_module(module.nearest_parent_mod());
         while module.span.ctxt().normalize_to_macros_2_0() != *ctxt {
             let parent = module.parent.unwrap_or_else(|| self.expn_def_scope(ctxt.remove_mark()));