2 files changed, 57 insertions, 19 deletions

diff --git a/crates/hir_def/src/nameres/collector.rs b/crates/hir_def/src/nameres/collector.rs
index d58135ec9..4ddc791ce 100644
--- a/crates/hir_def/src/nameres/collector.rs
+++ b/crates/hir_def/src/nameres/collector.rs
@@ -23,6 +23,7 @@ use crate::{
     attr::Attrs,
     db::DefDatabase,
     derive_macro_as_call_id,
+    intern::Interned,
     item_scope::{ImportType, PerNsGlobImports},
     item_tree::{
         self, FileItemTreeId, ItemTree, ItemTreeId, MacroCall, MacroDef, MacroRules, Mod, ModItem,
@@ -54,20 +55,22 @@ pub(super) fn collect_defs(
 ) -> DefMap {
     let crate_graph = db.crate_graph();
 
-    // populate external prelude
-    for dep in &crate_graph[def_map.krate].dependencies {
-        log::debug!("crate dep {:?} -> {:?}", dep.name, dep.crate_id);
-        let dep_def_map = db.crate_def_map(dep.crate_id);
-        def_map
-            .extern_prelude
-            .insert(dep.as_name(), dep_def_map.module_id(dep_def_map.root).into());
-
-        // look for the prelude
-        // If the dependency defines a prelude, we overwrite an already defined
-        // prelude. This is necessary to import the "std" prelude if a crate
-        // depends on both "core" and "std".
-        if dep_def_map.prelude.is_some() {
-            def_map.prelude = dep_def_map.prelude;
+    if block.is_none() {
+        // populate external prelude
+        for dep in &crate_graph[def_map.krate].dependencies {
+            log::debug!("crate dep {:?} -> {:?}", dep.name, dep.crate_id);
+            let dep_def_map = db.crate_def_map(dep.crate_id);
+            def_map
+                .extern_prelude
+                .insert(dep.as_name(), dep_def_map.module_id(dep_def_map.root).into());
+
+            // look for the prelude
+            // If the dependency defines a prelude, we overwrite an already defined
+            // prelude. This is necessary to import the "std" prelude if a crate
+            // depends on both "core" and "std".
+            if dep_def_map.prelude.is_some() {
+                def_map.prelude = dep_def_map.prelude;
+            }
         }
     }
 
@@ -106,7 +109,9 @@ pub(super) fn collect_defs(
         }
     }
     collector.collect();
-    collector.finish()
+    let mut def_map = collector.finish();
+    def_map.shrink_to_fit();
+    def_map
 }
 
 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
@@ -137,7 +142,7 @@ enum ImportSource {
 
 #[derive(Clone, Debug, Eq, PartialEq)]
 struct Import {
-    path: ModPath,
+    path: Interned<ModPath>,
     alias: Option<ImportAlias>,
     visibility: RawVisibility,
     is_glob: bool,
@@ -179,7 +184,10 @@ impl Import {
         let attrs = &tree.attrs(db, krate, ModItem::from(id.value).into());
         let visibility = &tree[it.visibility];
         Self {
-            path: ModPath::from_segments(PathKind::Plain, iter::once(it.name.clone())),
+            path: Interned::new(ModPath::from_segments(
+                PathKind::Plain,
+                iter::once(it.name.clone()),
+            )),
             alias: it.alias.clone(),
             visibility: visibility.clone(),
             is_glob: false,
@@ -1400,8 +1408,18 @@ impl ModCollector<'_, '_> {
 
         // Case 1: builtin macros
         if attrs.by_key("rustc_builtin_macro").exists() {
+            // `#[rustc_builtin_macro = "builtin_name"]` overrides the `macro_rules!` name.
+            let name;
+            let name = match attrs.by_key("rustc_builtin_macro").string_value() {
+                Some(it) => {
+                    // FIXME: a hacky way to create a Name from string.
+                    name = tt::Ident { text: it.clone(), id: tt::TokenId::unspecified() }.as_name();
+                    &name
+                }
+                None => &mac.name,
+            };
             let krate = self.def_collector.def_map.krate;
-            if let Some(macro_id) = find_builtin_macro(&mac.name, krate, ast_id) {
+            if let Some(macro_id) = find_builtin_macro(name, krate, ast_id) {
                 self.def_collector.define_macro_rules(
                     self.module_id,
                     mac.name.clone(),
@@ -1464,7 +1482,7 @@ impl ModCollector<'_, '_> {
     }
 
     fn collect_macro_call(&mut self, mac: &MacroCall) {
-        let mut ast_id = AstIdWithPath::new(self.file_id, mac.ast_id, mac.path.clone());
+        let mut ast_id = AstIdWithPath::new(self.file_id, mac.ast_id, (*mac.path).clone());
 
         // Case 1: try to resolve in legacy scope and expand macro_rules
         let mut error = None;
diff --git a/crates/hir_def/src/nameres/tests/diagnostics.rs b/crates/hir_def/src/nameres/tests/diagnostics.rs
index a89061c2e..fefdadb22 100644
--- a/crates/hir_def/src/nameres/tests/diagnostics.rs
+++ b/crates/hir_def/src/nameres/tests/diagnostics.rs
@@ -7,6 +7,11 @@ fn check_diagnostics(ra_fixture: &str) {
     db.check_diagnostics();
 }
 
+fn check_no_diagnostics(ra_fixture: &str) {
+    let db: TestDB = TestDB::with_files(ra_fixture);
+    db.check_no_diagnostics();
+}
+
 #[test]
 fn unresolved_import() {
     check_diagnostics(
@@ -202,6 +207,21 @@ fn builtin_macro_fails_expansion() {
 }
 
 #[test]
+fn include_macro_should_allow_empty_content() {
+    check_no_diagnostics(
+        r#"
+        //- /lib.rs
+          #[rustc_builtin_macro]
+          macro_rules! include { () => {} }
+
+          include!("bar.rs");
+        //- /bar.rs
+          // empty
+        "#,
+    );
+}
+
+#[test]
 fn good_out_dir_diagnostic() {
     check_diagnostics(
         r#"