Auto merge of #143550 - petrochenkov:lessmutres, r=<try>

[WIP] resolve: Use interior mutability for extern module map

Based on #143458.

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.

cc `@LorrensP-2158466`

Author: bors

compiler/rustc_expand/src/base.rs

@@ -1062,7 +1062,7 @@ pub trait ResolverExpand {
     fn next_node_id(&mut self) -> NodeId;
     fn invocation_parent(&self, id: LocalExpnId) -> LocalDefId;
 
-    fn resolve_dollar_crates(&mut self);
+    fn resolve_dollar_crates(&self);
     fn visit_ast_fragment_with_placeholders(
         &mut self,
         expn_id: LocalExpnId,

compiler/rustc_resolve/src/build_reduced_graph.rs

@@ -85,7 +85,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
     /// Reachable macros with block module parents exist due to `#[macro_export] macro_rules!`,
     /// but they cannot use def-site hygiene, so the assumption holds
     /// (<https://github.com/rust-lang/rust/pull/77984#issuecomment-712445508>).
-    pub(crate) fn get_nearest_non_block_module(&mut self, mut def_id: DefId) -> Module<'ra> {
+    pub(crate) fn get_nearest_non_block_module(&self, mut def_id: DefId) -> Module<'ra> {
         loop {
             match self.get_module(def_id) {
                 Some(module) => return module,
@@ -94,44 +94,47 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         }
     }
 
-    pub(crate) fn expect_module(&mut self, def_id: DefId) -> Module<'ra> {
+    pub(crate) fn expect_module(&self, def_id: DefId) -> Module<'ra> {
         self.get_module(def_id).expect("argument `DefId` is not a module")
     }
 
     /// If `def_id` refers to a module (in resolver's sense, i.e. a module item, crate root, enum,
     /// or trait), then this function returns that module's resolver representation, otherwise it
     /// returns `None`.
-    pub(crate) fn get_module(&mut self, def_id: DefId) -> Option<Module<'ra>> {
-        if let module @ Some(..) = self.module_map.get(&def_id) {
-            return module.copied();
-        }
+    pub(crate) fn get_module(&self, def_id: DefId) -> Option<Module<'ra>> {
+        match def_id.as_local() {
+            Some(local_def_id) => self.local_module_map.get(&local_def_id).copied(),
+            None => {
+                if let module @ Some(..) = self.extern_module_map.borrow().get(&def_id) {
+                    return module.copied();
+                }
 
-        if !def_id.is_local() {
-            // Query `def_kind` is not used because query system overhead is too expensive here.
-            let def_kind = self.cstore().def_kind_untracked(def_id);
-            if def_kind.is_module_like() {
-                let parent = self
-                    .tcx
-                    .opt_parent(def_id)
-                    .map(|parent_id| self.get_nearest_non_block_module(parent_id));
-                // Query `expn_that_defined` is not used because
-                // hashing spans in its result is expensive.
-                let expn_id = self.cstore().expn_that_defined_untracked(def_id, self.tcx.sess);
-                return Some(self.new_module(
-                    parent,
-                    ModuleKind::Def(def_kind, def_id, Some(self.tcx.item_name(def_id))),
-                    expn_id,
-                    self.def_span(def_id),
-                    // FIXME: Account for `#[no_implicit_prelude]` attributes.
-                    parent.is_some_and(|module| module.no_implicit_prelude),
-                ));
+                // Query `def_kind` is not used because query system overhead is too expensive here.
+                let def_kind = self.cstore().def_kind_untracked(def_id);
+                if def_kind.is_module_like() {
+                    let parent = self
+                        .tcx
+                        .opt_parent(def_id)
+                        .map(|parent_id| self.get_nearest_non_block_module(parent_id));
+                    // Query `expn_that_defined` is not used because
+                    // hashing spans in its result is expensive.
+                    let expn_id = self.cstore().expn_that_defined_untracked(def_id, self.tcx.sess);
+                    return Some(self.new_extern_module(
+                        parent,
+                        ModuleKind::Def(def_kind, def_id, Some(self.tcx.item_name(def_id))),
+                        expn_id,
+                        self.def_span(def_id),
+                        // FIXME: Account for `#[no_implicit_prelude]` attributes.
+                        parent.is_some_and(|module| module.no_implicit_prelude),
+                    ));
+                }
+
+                None
             }
         }
-
-        None
     }
 
-    pub(crate) fn expn_def_scope(&mut self, expn_id: ExpnId) -> Module<'ra> {
+    pub(crate) fn expn_def_scope(&self, expn_id: ExpnId) -> Module<'ra> {
         match expn_id.expn_data().macro_def_id {
             Some(def_id) => self.macro_def_scope(def_id),
             None => expn_id
@@ -141,7 +144,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         }
     }
 
-    pub(crate) fn macro_def_scope(&mut self, def_id: DefId) -> Module<'ra> {
+    pub(crate) fn macro_def_scope(&self, def_id: DefId) -> Module<'ra> {
         if let Some(id) = def_id.as_local() {
             self.local_macro_def_scopes[&id]
         } else {
@@ -403,7 +406,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
         self.r.field_visibility_spans.insert(def_id, field_vis);
     }
 
-    fn block_needs_anonymous_module(&mut self, block: &Block) -> bool {
+    fn block_needs_anonymous_module(&self, block: &Block) -> bool {
         // If any statements are items, we need to create an anonymous module
         block
             .stmts
@@ -758,7 +761,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
                 if let ast::ModKind::Loaded(_, _, _, Err(_)) = mod_kind {
                     self.r.mods_with_parse_errors.insert(def_id);
                 }
-                self.parent_scope.module = self.r.new_module(
+                self.parent_scope.module = self.r.new_local_module(
                     Some(parent),
                     ModuleKind::Def(def_kind, def_id, Some(ident.name)),
                     expansion.to_expn_id(),
@@ -790,7 +793,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
             ItemKind::Enum(ident, _, _) | ItemKind::Trait(box ast::Trait { ident, .. }) => {
                 self.r.define(parent, ident, TypeNS, res, vis, sp, expansion);
 
-                self.parent_scope.module = self.r.new_module(
+                self.parent_scope.module = self.r.new_local_module(
                     Some(parent),
                     ModuleKind::Def(def_kind, def_id, Some(ident.name)),
                     expansion.to_expn_id(),
@@ -986,7 +989,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
         let parent = self.parent_scope.module;
         let expansion = self.parent_scope.expansion;
         if self.block_needs_anonymous_module(block) {
-            let module = self.r.new_module(
+            let module = self.r.new_local_module(
                 Some(parent),
                 ModuleKind::Block,
                 expansion.to_expn_id(),
@@ -1118,7 +1121,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
     }
 
     /// Returns `true` if this attribute list contains `macro_use`.
-    fn contains_macro_use(&mut self, attrs: &[ast::Attribute]) -> bool {
+    fn contains_macro_use(&self, attrs: &[ast::Attribute]) -> bool {
         for attr in attrs {
             if attr.has_name(sym::macro_escape) {
                 let inner_attribute = matches!(attr.style, ast::AttrStyle::Inner);

compiler/rustc_resolve/src/diagnostics.rs

@@ -2150,7 +2150,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
     }
 
     pub(crate) fn find_similarly_named_module_or_crate(
-        &mut self,
+        &self,
         ident: Symbol,
         current_module: Module<'ra>,
     ) -> Option<Symbol> {
@@ -2159,7 +2159,16 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             .keys()
             .map(|ident| ident.name)
             .chain(
-                self.module_map
+                self.local_module_map
+                    .iter()
+                    .filter(|(_, module)| {
+                        current_module.is_ancestor_of(**module) && current_module != **module
+                    })
+                    .flat_map(|(_, module)| module.kind.name()),
+            )
+            .chain(
+                self.extern_module_map
+                    .borrow()
                     .iter()
                     .filter(|(_, module)| {
                         current_module.is_ancestor_of(**module) && current_module != **module
@@ -2435,7 +2444,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
     }
 
     fn undeclared_module_suggest_declare(
-        &mut self,
+        &self,
         ident: Ident,
         path: std::path::PathBuf,
     ) -> Option<(Vec<(Span, String)>, String, Applicability)> {
@@ -2450,7 +2459,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         ))
     }
 
-    fn undeclared_module_exists(&mut self, ident: Ident) -> Option<std::path::PathBuf> {
+    fn undeclared_module_exists(&self, ident: Ident) -> Option<std::path::PathBuf> {
         let map = self.tcx.sess.source_map();
 
         let src = map.span_to_filename(ident.span).into_local_path()?;
@@ -2809,24 +2818,23 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     return cached;
                 }
                 visited.insert(parent_module, false);
-                let res = r.module_map.get(&parent_module).is_some_and(|m| {
-                    for importer in m.glob_importers.borrow().iter() {
-                        if let Some(next_parent_module) = importer.parent_scope.module.opt_def_id()
+                let m = r.expect_module(parent_module);
+                let mut res = false;
+                for importer in m.glob_importers.borrow().iter() {
+                    if let Some(next_parent_module) = importer.parent_scope.module.opt_def_id() {
+                        if next_parent_module == module
+                            || comes_from_same_module_for_glob(
+                                r,
+                                next_parent_module,
+                                module,
+                                visited,
+                            )
                         {
-                            if next_parent_module == module
-                                || comes_from_same_module_for_glob(
-                                    r,
-                                    next_parent_module,
-                                    module,
-                                    visited,
-                                )
-                            {
-                                return true;
-                            }
+                            res = true;
+                            break;
                         }
                     }
-                    false
-                });
+                }
                 visited.insert(parent_module, res);
                 res
             }

compiler/rustc_resolve/src/effective_visibilities.rs

@@ -38,11 +38,11 @@ pub(crate) struct EffectiveVisibilitiesVisitor<'a, 'ra, 'tcx> {
 }
 
 impl Resolver<'_, '_> {
-    fn nearest_normal_mod(&mut self, def_id: LocalDefId) -> LocalDefId {
+    fn nearest_normal_mod(&self, def_id: LocalDefId) -> LocalDefId {
         self.get_nearest_non_block_module(def_id.to_def_id()).nearest_parent_mod().expect_local()
     }
 
-    fn private_vis_import(&mut self, binding: NameBinding<'_>) -> Visibility {
+    fn private_vis_import(&self, binding: NameBinding<'_>) -> Visibility {
         let NameBindingKind::Import { import, .. } = binding.kind else { unreachable!() };
         Visibility::Restricted(
             import
@@ -52,7 +52,7 @@ impl Resolver<'_, '_> {
         )
     }
 
-    fn private_vis_def(&mut self, def_id: LocalDefId) -> Visibility {
+    fn private_vis_def(&self, def_id: LocalDefId) -> Visibility {
         // For mod items `nearest_normal_mod` returns its argument, but we actually need its parent.
         let normal_mod_id = self.nearest_normal_mod(def_id);
         if normal_mod_id == def_id {
@@ -113,8 +113,7 @@ impl<'a, 'ra, 'tcx> EffectiveVisibilitiesVisitor<'a, 'ra, 'tcx> {
     /// Update effective visibilities of bindings in the given module,
     /// including their whole reexport chains.
     fn set_bindings_effective_visibilities(&mut self, module_id: LocalDefId) {
-        assert!(self.r.module_map.contains_key(&module_id.to_def_id()));
-        let module = self.r.get_module(module_id.to_def_id()).unwrap();
+        let module = self.r.expect_module(module_id.to_def_id());
         let resolutions = self.r.resolutions(module);
 
         for (_, name_resolution) in resolutions.borrow().iter() {

compiler/rustc_resolve/src/ident.rs

@@ -841,7 +841,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                 if ns == TypeNS {
                     if ident.name == kw::Crate || ident.name == kw::DollarCrate {
                         let module = self.resolve_crate_root(ident);
-                        return Ok(self.module_self_bindings[&module]);
+                        return Ok(module.self_binding.unwrap());
                     } else if ident.name == kw::Super || ident.name == kw::SelfLower {
                         // FIXME: Implement these with renaming requirements so that e.g.
                         // `use super;` doesn't work, but `use super as name;` does.
@@ -885,7 +885,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             );
         }
 
-        let check_usable = |this: &mut Self, binding: NameBinding<'ra>| {
+        let check_usable = |this: &Self, binding: NameBinding<'ra>| {
             let usable = this.is_accessible_from(binding.vis, parent_scope.module);
             if usable { Ok(binding) } else { Err((Determined, Weak::No)) }
         };

compiler/rustc_resolve/src/imports.rs

@@ -456,7 +456,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         f: F,
     ) -> T
     where
-        F: FnOnce(&mut Resolver<'ra, 'tcx>, &mut NameResolution<'ra>) -> T,
+        F: FnOnce(&Resolver<'ra, 'tcx>, &mut NameResolution<'ra>) -> T,
     {
         // Ensure that `resolution` isn't borrowed when defining in the module's glob importers,
         // during which the resolution might end up getting re-defined via a glob cycle.

compiler/rustc_resolve/src/late.rs

@@ -2491,7 +2491,7 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
 
     /// Searches the current set of local scopes for labels. Returns the `NodeId` of the resolved
     /// label and reports an error if the label is not found or is unreachable.
-    fn resolve_label(&mut self, mut label: Ident) -> Result<(NodeId, Span), ResolutionError<'ra>> {
+    fn resolve_label(&self, mut label: Ident) -> Result<(NodeId, Span), ResolutionError<'ra>> {
         let mut suggestion = None;
 
         for i in (0..self.label_ribs.len()).rev() {