Add macro_use prelude to DefMap

crates/hir-def/src/nameres.rs

@@ -105,6 +105,9 @@ pub struct DefMap {
     prelude: Option<ModuleId>,
     /// The extern prelude is only populated for non-block DefMaps
     extern_prelude: FxHashMap<Name, ModuleId>,
+    /// `macro_use` prelude that contains macros from `#[macro_use]`'d external crates. Note that
+    /// this contains all kinds of macro, not just `macro_rules!` macro.
+    macro_use_prelude: FxHashMap<Name, MacroId>,
 
     /// Side table for resolving derive helpers.
     exported_derives: FxHashMap<MacroDefId, Box<[Name]>>,
@@ -277,6 +280,7 @@ impl DefMap {
             edition,
             recursion_limit: None,
             extern_prelude: FxHashMap::default(),
+            macro_use_prelude: FxHashMap::default(),
             exported_derives: FxHashMap::default(),
             fn_proc_macro_mapping: FxHashMap::default(),
             proc_macro_loading_error: None,
@@ -489,6 +493,7 @@ impl DefMap {
             _c: _,
             exported_derives,
             extern_prelude,
+            macro_use_prelude,
             diagnostics,
             modules,
             registered_attrs,
@@ -507,6 +512,7 @@ impl DefMap {
         } = self;
 
         extern_prelude.shrink_to_fit();
+        macro_use_prelude.shrink_to_fit();
         exported_derives.shrink_to_fit();
         diagnostics.shrink_to_fit();
         modules.shrink_to_fit();

crates/hir-def/src/nameres/collector.rs

@@ -707,6 +707,7 @@ impl DefCollector<'_> {
     }
 
     /// Import macros from `#[macro_use] extern crate`.
+    // FIXME: Support `#[macro_rules(macro_name, ...)]`.
     fn import_macros_from_extern_crate(
         &mut self,
         current_module_id: LocalModuleId,
@@ -725,7 +726,7 @@ impl DefCollector<'_> {
             }
 
             cov_mark::hit!(macro_rules_from_other_crates_are_visible_with_macro_use);
-            self.import_all_macros_exported(current_module_id, m.krate);
+            self.import_all_macros_exported(m.krate);
         }
     }
 
@@ -734,11 +735,12 @@ impl DefCollector<'_> {
     /// Exported macros are just all macros in the root module scope.
     /// Note that it contains not only all `#[macro_export]` macros, but also all aliases
     /// created by `use` in the root module, ignoring the visibility of `use`.
-    fn import_all_macros_exported(&mut self, current_module_id: LocalModuleId, krate: CrateId) {
+    fn import_all_macros_exported(&mut self, krate: CrateId) {
         let def_map = self.db.crate_def_map(krate);
         for (name, def) in def_map[def_map.root].scope.macros() {
-            // `#[macro_use]` brings macros into legacy scope. Yes, even non-`macro_rules!` macros.
-            self.define_legacy_macro(current_module_id, name.clone(), def);
+            // `#[macro_use]` brings macros into macro_use prelude. Yes, even non-`macro_rules!`
+            // macros.
+            self.def_map.macro_use_prelude.insert(name.clone(), def);
         }
     }
 
@@ -1509,6 +1511,7 @@ impl ModCollector<'_, '_> {
 
     fn collect(&mut self, items: &[ModItem], container: ItemContainerId) {
         let krate = self.def_collector.def_map.krate;
+        let is_crate_root = self.module_id == self.def_collector.def_map.root;
 
         // Note: don't assert that inserted value is fresh: it's simply not true
         // for macros.
@@ -1516,19 +1519,24 @@ impl ModCollector<'_, '_> {
 
         // Prelude module is always considered to be `#[macro_use]`.
         if let Some(prelude_module) = self.def_collector.def_map.prelude {
-            if prelude_module.krate != krate {
+            if prelude_module.krate != krate && is_crate_root {
                 cov_mark::hit!(prelude_is_macro_use);
-                self.def_collector.import_all_macros_exported(self.module_id, prelude_module.krate);
+                self.def_collector.import_all_macros_exported(prelude_module.krate);
             }
         }
 
         // This should be processed eagerly instead of deferred to resolving.
         // `#[macro_use] extern crate` is hoisted to imports macros before collecting
         // any other items.
-        for &item in items {
-            let attrs = self.item_tree.attrs(self.def_collector.db, krate, item.into());
-            if attrs.cfg().map_or(true, |cfg| self.is_cfg_enabled(&cfg)) {
-                if let ModItem::ExternCrate(id) = item {
+        //
+        // If we're not at the crate root, `macro_use`d extern crates are an error so let's just
+        // ignore them.
+        // FIXME: Support `#[macro_rules(macro_name, ...)]`.
+        if is_crate_root {
+            for &item in items {
+                let ModItem::ExternCrate(id) = item else { continue; };
+                let attrs = self.item_tree.attrs(self.def_collector.db, krate, item.into());
+                if attrs.cfg().map_or(true, |cfg| self.is_cfg_enabled(&cfg)) {
                     let import = &self.item_tree[id];
                     let attrs = self.item_tree.attrs(
                         self.def_collector.db,

crates/hir-def/src/nameres/path_resolution.rs

@@ -385,7 +385,7 @@ impl DefMap {
         // Resolve in:
         //  - legacy scope of macro
         //  - current module / scope
-        //  - extern prelude
+        //  - extern prelude / macro_use prelude
         //  - std prelude
         let from_legacy_macro = self[module]
             .scope
@@ -414,9 +414,18 @@ impl DefMap {
                 .get(name)
                 .map_or(PerNs::none(), |&it| PerNs::types(it.into(), Visibility::Public))
         };
+        let macro_use_prelude = || {
+            self.macro_use_prelude
+                .get(name)
+                .map_or(PerNs::none(), |&it| PerNs::macros(it.into(), Visibility::Public))
+        };
         let prelude = || self.resolve_in_prelude(db, name);
 
-        from_legacy_macro.or(from_scope_or_builtin).or_else(extern_prelude).or_else(prelude)
+        from_legacy_macro
+            .or(from_scope_or_builtin)
+            .or_else(extern_prelude)
+            .or_else(macro_use_prelude)
+            .or_else(prelude)
     }
 
     fn resolve_name_in_crate_root_or_extern_prelude(

crates/hir-def/src/nameres/tests/macros.rs

@@ -1216,17 +1216,58 @@ fn proc_attr(a: TokenStream, b: TokenStream) -> TokenStream { a }
     "#,
     );
 
-    let root = &def_map[def_map.root()].scope;
-    let actual = root
-        .legacy_macros()
-        .sorted_by(|a, b| std::cmp::Ord::cmp(&a.0, &b.0))
-        .map(|(name, _)| format!("{name}\n"))
-        .collect::<String>();
+    let root_module = &def_map[def_map.root()].scope;
+    assert!(
+        root_module.legacy_macros().count() == 0,
+        "`#[macro_use]` shouldn't bring macros into textual macro scope",
+    );
+
+    let actual = def_map.macro_use_prelude.iter().map(|(name, _)| name).sorted().join("\n");
 
     expect![[r#"
         legacy
         macro20
-        proc_attr
-    "#]]
+        proc_attr"#]]
     .assert_eq(&actual);
 }
+
+#[test]
+fn non_prelude_macros_take_precedence_over_macro_use_prelude() {
+    check(
+        r#"
+//- /lib.rs edition:2021 crate:lib deps:dep,core
+#[macro_use]
+extern crate dep;
+
+macro foo() { struct Ok; }
+macro bar() { fn ok() {} }
+
+foo!();
+bar!();
+
+//- /dep.rs crate:dep
+#[macro_export]
+macro_rules! foo {
+    () => { struct NotOk; }
+}
+
+//- /core.rs crate:core
+pub mod prelude {
+    pub mod rust_2021 {
+        #[macro_export]
+        macro_rules! bar {
+            () => { fn not_ok() {} }
+        }
+    }
+}
+        "#,
+        expect![[r#"
+            crate
+            Ok: t v
+            bar: m
+            dep: t
+            foo: m
+            ok: v
+        "#]],
+    );
+}