10 files changed, 128 insertions, 11 deletions

diff --git a/crates/hir/src/lib.rs b/crates/hir/src/lib.rs
index dba46df04..debc3ee62 100644
--- a/crates/hir/src/lib.rs
+++ b/crates/hir/src/lib.rs
@@ -1344,6 +1344,7 @@ impl MacroDef {
             MacroDefKind::Declarative(_) => MacroKind::Declarative,
             MacroDefKind::BuiltIn(_, _) | MacroDefKind::BuiltInEager(_, _) => MacroKind::BuiltIn,
             MacroDefKind::BuiltInDerive(_, _) => MacroKind::Derive,
+            MacroDefKind::BuiltInAttr(_, _) => MacroKind::Attr,
             MacroDefKind::ProcMacro(_, base_db::ProcMacroKind::CustomDerive, _) => {
                 MacroKind::Derive
             }
diff --git a/crates/hir_def/src/nameres/collector.rs b/crates/hir_def/src/nameres/collector.rs
index d019ba3a9..93f30f23d 100644
--- a/crates/hir_def/src/nameres/collector.rs
+++ b/crates/hir_def/src/nameres/collector.rs
@@ -9,6 +9,7 @@ use base_db::{CrateId, Edition, FileId, ProcMacroId};
 use cfg::{CfgExpr, CfgOptions};
 use hir_expand::{
     ast_id_map::FileAstId,
+    builtin_attr::find_builtin_attr,
     builtin_derive::find_builtin_derive,
     builtin_macro::find_builtin_macro,
     name::{name, AsName, Name},
@@ -1836,7 +1837,8 @@ impl ModCollector<'_, '_> {
         let attrs = self.item_tree.attrs(self.def_collector.db, krate, ModItem::from(id).into());
         if attrs.by_key("rustc_builtin_macro").exists() {
             let macro_id = find_builtin_macro(&mac.name, krate, ast_id)
-                .or_else(|| find_builtin_derive(&mac.name, krate, ast_id));
+                .or_else(|| find_builtin_derive(&mac.name, krate, ast_id))
+                .or_else(|| find_builtin_attr(&mac.name, krate, ast_id));
 
             match macro_id {
                 Some(macro_id) => {
diff --git a/crates/hir_expand/src/builtin_attr.rs b/crates/hir_expand/src/builtin_attr.rs
new file mode 100644
index 000000000..c8432005e
--- /dev/null
+++ b/crates/hir_expand/src/builtin_attr.rs
@@ -0,0 +1,67 @@
+//! Builtin derives.
+
+use syntax::ast;
+
+use crate::{db::AstDatabase, name, AstId, CrateId, MacroCallId, MacroDefId, MacroDefKind};
+
+macro_rules! register_builtin {
+    ( $(($name:ident, $variant:ident) => $expand:ident),* ) => {
+        #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+        pub enum BuiltinAttrExpander {
+            $($variant),*
+        }
+
+        impl BuiltinAttrExpander {
+            pub fn expand(
+                &self,
+                db: &dyn AstDatabase,
+                id: MacroCallId,
+                tt: &tt::Subtree,
+            ) -> Result<tt::Subtree, mbe::ExpandError> {
+                let expander = match *self {
+                    $( BuiltinAttrExpander::$variant => $expand, )*
+                };
+                expander(db, id, tt)
+            }
+
+            fn find_by_name(name: &name::Name) -> Option<Self> {
+                match name {
+                    $( id if id == &name::name![$name] => Some(BuiltinAttrExpander::$variant), )*
+                     _ => None,
+                }
+            }
+        }
+
+    };
+}
+
+register_builtin! {
+    (bench, Bench) => dummy_attr_expand,
+    (cfg_accessible, CfgAccessible) => dummy_attr_expand,
+    (cfg_eval, CfgEval) => dummy_attr_expand,
+    (derive, Derive) => dummy_attr_expand,
+    (global_allocator, GlobalAllocator) => dummy_attr_expand,
+    (test, Test) => dummy_attr_expand,
+    (test_case, TestCase) => dummy_attr_expand
+}
+
+pub fn find_builtin_attr(
+    ident: &name::Name,
+    krate: CrateId,
+    ast_id: AstId<ast::Macro>,
+) -> Option<MacroDefId> {
+    let expander = BuiltinAttrExpander::find_by_name(ident)?;
+    Some(MacroDefId {
+        krate,
+        kind: MacroDefKind::BuiltInAttr(expander, ast_id),
+        local_inner: false,
+    })
+}
+
+fn dummy_attr_expand(
+    _db: &dyn AstDatabase,
+    _id: MacroCallId,
+    tt: &tt::Subtree,
+) -> Result<tt::Subtree, mbe::ExpandError> {
+    Ok(tt.clone())
+}
diff --git a/crates/hir_expand/src/db.rs b/crates/hir_expand/src/db.rs
index 18a05579f..45e6e446a 100644
--- a/crates/hir_expand/src/db.rs
+++ b/crates/hir_expand/src/db.rs
@@ -12,9 +12,9 @@ use syntax::{
 };
 
 use crate::{
-    ast_id_map::AstIdMap, hygiene::HygieneFrame, input::process_macro_input, BuiltinDeriveExpander,
-    BuiltinFnLikeExpander, HirFileId, HirFileIdRepr, MacroCallId, MacroCallKind, MacroCallLoc,
-    MacroDefId, MacroDefKind, MacroFile, ProcMacroExpander,
+    ast_id_map::AstIdMap, hygiene::HygieneFrame, input::process_macro_input, BuiltinAttrExpander,
+    BuiltinDeriveExpander, BuiltinFnLikeExpander, HirFileId, HirFileIdRepr, MacroCallId,
+    MacroCallKind, MacroCallLoc, MacroDefId, MacroDefKind, MacroFile, ProcMacroExpander,
 };
 
 /// Total limit on the number of tokens produced by any macro invocation.
@@ -31,6 +31,8 @@ pub enum TokenExpander {
     MacroDef { mac: mbe::MacroDef, def_site_token_map: mbe::TokenMap },
     /// Stuff like `line!` and `file!`.
     Builtin(BuiltinFnLikeExpander),
+    /// `global_allocator` and such.
+    BuiltinAttr(BuiltinAttrExpander),
     /// `derive(Copy)` and such.
     BuiltinDerive(BuiltinDeriveExpander),
     /// The thing we love the most here in rust-analyzer -- procedural macros.
@@ -49,6 +51,7 @@ impl TokenExpander {
             TokenExpander::MacroDef { mac, .. } => mac.expand(tt),
             TokenExpander::Builtin(it) => it.expand(db, id, tt),
             // FIXME switch these to ExpandResult as well
+            TokenExpander::BuiltinAttr(it) => it.expand(db, id, tt).into(),
             TokenExpander::BuiltinDerive(it) => it.expand(db, id, tt).into(),
             TokenExpander::ProcMacro(_) => {
                 // We store the result in salsa db to prevent non-deterministic behavior in
@@ -64,6 +67,7 @@ impl TokenExpander {
             TokenExpander::MacroRules { mac, .. } => mac.map_id_down(id),
             TokenExpander::MacroDef { mac, .. } => mac.map_id_down(id),
             TokenExpander::Builtin(..)
+            | TokenExpander::BuiltinAttr(..)
             | TokenExpander::BuiltinDerive(..)
             | TokenExpander::ProcMacro(..) => id,
         }
@@ -74,6 +78,7 @@ impl TokenExpander {
             TokenExpander::MacroRules { mac, .. } => mac.map_id_up(id),
             TokenExpander::MacroDef { mac, .. } => mac.map_id_up(id),
             TokenExpander::Builtin(..)
+            | TokenExpander::BuiltinAttr(..)
             | TokenExpander::BuiltinDerive(..)
             | TokenExpander::ProcMacro(..) => (id, mbe::Origin::Call),
         }
@@ -299,6 +304,9 @@ fn macro_def(db: &dyn AstDatabase, id: MacroDefId) -> Option<Arc<TokenExpander>>
             }
         },
         MacroDefKind::BuiltIn(expander, _) => Some(Arc::new(TokenExpander::Builtin(expander))),
+        MacroDefKind::BuiltInAttr(expander, _) => {
+            Some(Arc::new(TokenExpander::BuiltinAttr(expander)))
+        }
         MacroDefKind::BuiltInDerive(expander, _) => {
             Some(Arc::new(TokenExpander::BuiltinDerive(expander)))
         }
diff --git a/crates/hir_expand/src/eager.rs b/crates/hir_expand/src/eager.rs
index 14af628a1..9093255f4 100644
--- a/crates/hir_expand/src/eager.rs
+++ b/crates/hir_expand/src/eager.rs
@@ -224,6 +224,7 @@ fn eager_macro_recur(
             }
             MacroDefKind::Declarative(_)
             | MacroDefKind::BuiltIn(..)
+            | MacroDefKind::BuiltInAttr(..)
             | MacroDefKind::BuiltInDerive(..)
             | MacroDefKind::ProcMacro(..) => {
                 let res = lazy_expand(db, &def, curr.with_value(child.clone()), krate);
diff --git a/crates/hir_expand/src/hygiene.rs b/crates/hir_expand/src/hygiene.rs
index d98913907..05c6c3fb1 100644
--- a/crates/hir_expand/src/hygiene.rs
+++ b/crates/hir_expand/src/hygiene.rs
@@ -192,6 +192,7 @@ impl HygieneFrame {
                         (info, Some(loc.def.krate), loc.def.local_inner)
                     }
                     MacroDefKind::BuiltIn(..) => (info, Some(loc.def.krate), false),
+                    MacroDefKind::BuiltInAttr(..) => (info, None, false),
                     MacroDefKind::BuiltInDerive(..) => (info, None, false),
                     MacroDefKind::BuiltInEager(..) => (info, None, false),
                     MacroDefKind::ProcMacro(..) => (info, None, false),
diff --git a/crates/hir_expand/src/lib.rs b/crates/hir_expand/src/lib.rs
index 618f26b95..623791b58 100644
--- a/crates/hir_expand/src/lib.rs
+++ b/crates/hir_expand/src/lib.rs
@@ -8,6 +8,7 @@ pub mod db;
 pub mod ast_id_map;
 pub mod name;
 pub mod hygiene;
+pub mod builtin_attr;
 pub mod builtin_derive;
 pub mod builtin_macro;
 pub mod proc_macro;
@@ -32,6 +33,7 @@ use syntax::{
 };
 
 use crate::ast_id_map::FileAstId;
+use crate::builtin_attr::BuiltinAttrExpander;
 use crate::builtin_derive::BuiltinDeriveExpander;
 use crate::builtin_macro::{BuiltinFnLikeExpander, EagerExpander};
 use crate::proc_macro::ProcMacroExpander;
@@ -206,6 +208,7 @@ impl MacroDefId {
         let id = match &self.kind {
             MacroDefKind::Declarative(id) => id,
             MacroDefKind::BuiltIn(_, id) => id,
+            MacroDefKind::BuiltInAttr(_, id) => id,
             MacroDefKind::BuiltInDerive(_, id) => id,
             MacroDefKind::BuiltInEager(_, id) => id,
             MacroDefKind::ProcMacro(.., id) => return Either::Right(*id),
@@ -223,6 +226,7 @@ pub enum MacroDefKind {
     Declarative(AstId<ast::Macro>),
     BuiltIn(BuiltinFnLikeExpander, AstId<ast::Macro>),
     // FIXME: maybe just Builtin and rename BuiltinFnLikeExpander to BuiltinExpander
+    BuiltInAttr(BuiltinAttrExpander, AstId<ast::Macro>),
     BuiltInDerive(BuiltinDeriveExpander, AstId<ast::Macro>),
     BuiltInEager(EagerExpander, AstId<ast::Macro>),
     ProcMacro(ProcMacroExpander, ProcMacroKind, AstId<ast::Fn>),
diff --git a/crates/hir_expand/src/name.rs b/crates/hir_expand/src/name.rs
index 00b8adc1e..376fe130f 100644
--- a/crates/hir_expand/src/name.rs
+++ b/crates/hir_expand/src/name.rs
@@ -160,7 +160,6 @@ pub mod known {
         str,
         // Special names
         macro_rules,
-        derive,
         doc,
         cfg,
         cfg_attr,
@@ -240,6 +239,14 @@ pub mod known {
         PartialOrd,
         Eq,
         PartialEq,
+        // Builtin attributes
+        bench,
+        cfg_accessible,
+        cfg_eval,
+        derive,
+        global_allocator,
+        test,
+        test_case,
         // Safe intrinsics
         abort,
         size_of,
diff --git a/crates/ide_completion/src/completions/qualified_path.rs b/crates/ide_completion/src/completions/qualified_path.rs
index 0b0a81410..58d4dd9ee 100644
--- a/crates/ide_completion/src/completions/qualified_path.rs
+++ b/crates/ide_completion/src/completions/qualified_path.rs
@@ -657,6 +657,32 @@ fn main() { let _ = crate::$0 }
     }
 
     #[test]
+    fn does_not_complete_non_fn_macros() {
+        check(
+            r#"
+mod m {
+    #[rustc_builtin_macro]
+    pub macro Clone {}
+}
+
+fn f() {m::$0}
+"#,
+            expect![[r#""#]],
+        );
+        check(
+            r#"
+mod m {
+    #[rustc_builtin_macro]
+    pub macro bench {}
+}
+
+fn f() {m::$0}
+"#,
+            expect![[r#""#]],
+        );
+    }
+
+    #[test]
     fn completes_in_assoc_item_list() {
         check(
             r#"
diff --git a/crates/ide_completion/src/completions/unqualified_path.rs b/crates/ide_completion/src/completions/unqualified_path.rs
index 1f6c4069f..b1e6b2b77 100644
--- a/crates/ide_completion/src/completions/unqualified_path.rs
+++ b/crates/ide_completion/src/completions/unqualified_path.rs
@@ -481,14 +481,14 @@ impl S {
         );
         check(
             r#"
-mod m {
-    #[rustc_builtin_macro]
-    pub macro Clone {}
-}
+#[rustc_builtin_macro]
+pub macro bench {}
 
-fn f() {m::$0}
+fn f() {$0}
 "#,
-            expect![[r#""#]],
+            expect![[r#"
+                fn f() fn()
+            "#]],
         );
     }