10 files changed, 168 insertions, 35 deletions

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/builtin_derive.rs b/crates/hir_expand/src/builtin_derive.rs
index fe9497b50..4610f6f91 100644
--- a/crates/hir_expand/src/builtin_derive.rs
+++ b/crates/hir_expand/src/builtin_derive.rs
@@ -325,7 +325,7 @@ $0
             },
         };
 
-        let id: MacroCallId = db.intern_macro(loc).into();
+        let id: MacroCallId = db.intern_macro(loc);
         let parsed = db.parse_or_expand(id.as_file()).unwrap();
 
         // FIXME text() for syntax nodes parsed from token tree looks weird
diff --git a/crates/hir_expand/src/builtin_macro.rs b/crates/hir_expand/src/builtin_macro.rs
index 0b310ba2f..f24d1d919 100644
--- a/crates/hir_expand/src/builtin_macro.rs
+++ b/crates/hir_expand/src/builtin_macro.rs
@@ -354,7 +354,7 @@ fn concat_expand(
                 // concat works with string and char literals, so remove any quotes.
                 // It also works with integer, float and boolean literals, so just use the rest
                 // as-is.
-                let component = unquote_str(&it).unwrap_or_else(|| it.text.to_string());
+                let component = unquote_str(it).unwrap_or_else(|| it.text.to_string());
                 text.push_str(&component);
             }
             // handle boolean literals
@@ -417,7 +417,7 @@ fn parse_string(tt: &tt::Subtree) -> Result<String, mbe::ExpandError> {
     tt.token_trees
         .get(0)
         .and_then(|tt| match tt {
-            tt::TokenTree::Leaf(tt::Leaf::Literal(it)) => unquote_str(&it),
+            tt::TokenTree::Leaf(tt::Leaf::Literal(it)) => unquote_str(it),
             _ => None,
         })
         .ok_or_else(|| mbe::ExpandError::ConversionError)
@@ -430,7 +430,7 @@ fn include_expand(
 ) -> ExpandResult<Option<ExpandedEager>> {
     let res = (|| {
         let path = parse_string(tt)?;
-        let file_id = relative_file(db, arg_id.into(), &path, false)?;
+        let file_id = relative_file(db, arg_id, &path, false)?;
 
         let subtree = parse_to_token_tree(&db.file_text(file_id))
             .ok_or_else(|| mbe::ExpandError::ConversionError)?
@@ -480,7 +480,7 @@ fn include_str_expand(
     // it's unusual to `include_str!` a Rust file), but we can return an empty string.
     // Ideally, we'd be able to offer a precise expansion if the user asks for macro
     // expansion.
-    let file_id = match relative_file(db, arg_id.into(), &path, true) {
+    let file_id = match relative_file(db, arg_id, &path, true) {
         Ok(file_id) => file_id,
         Err(_) => {
             return ExpandResult::ok(Some(ExpandedEager::new(quote!(""))));
@@ -561,7 +561,7 @@ mod tests {
     use syntax::ast::NameOwner;
 
     fn expand_builtin_macro(ra_fixture: &str) -> String {
-        let (db, file_id) = TestDB::with_single_file(&ra_fixture);
+        let (db, file_id) = TestDB::with_single_file(ra_fixture);
         let parsed = db.parse(file_id);
         let mut macro_rules: Vec<_> =
             parsed.syntax_node().descendants().filter_map(ast::MacroRules::cast).collect();
@@ -598,7 +598,7 @@ mod tests {
                     },
                 };
 
-                let id: MacroCallId = db.intern_macro(loc).into();
+                let id: MacroCallId = db.intern_macro(loc);
                 id.as_file()
             }
             Either::Right(expander) => {
@@ -635,7 +635,7 @@ mod tests {
                     kind: MacroCallKind::FnLike { ast_id: call_id, fragment },
                 };
 
-                let id: MacroCallId = db.intern_macro(loc).into();
+                let id: MacroCallId = db.intern_macro(loc);
                 id.as_file()
             }
         };
diff --git a/crates/hir_expand/src/db.rs b/crates/hir_expand/src/db.rs
index e8f4af309..66f44202b 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, 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.
@@ -49,12 +51,13 @@ 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
                 // some proc-macro implementation
                 // See #4315 for details
-                db.expand_proc_macro(id.into()).into()
+                db.expand_proc_macro(id).into()
             }
         }
     }
@@ -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),
         }
@@ -85,7 +90,7 @@ impl TokenExpander {
 pub trait AstDatabase: SourceDatabase {
     fn ast_id_map(&self, file_id: HirFileId) -> Arc<AstIdMap>;
 
-    /// Main public API -- parsis a hir file, not caring whether it's a real
+    /// Main public API -- parses a hir file, not caring whether it's a real
     /// file or a macro expansion.
     #[salsa::transparent]
     fn parse_or_expand(&self, file_id: HirFileId) -> Option<SyntaxNode>;
@@ -236,7 +241,7 @@ fn parse_macro_expansion(
                 }
             };
             if is_self_replicating(&node, &call_node.value) {
-                return ExpandResult::only_err(err);
+                ExpandResult::only_err(err)
             } else {
                 ExpandResult { value: Some((parse, Arc::new(rev_token_map))), err: Some(err) }
             }
@@ -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)))
         }
@@ -377,7 +385,12 @@ fn expand_proc_macro(
         _ => unreachable!(),
     };
 
-    expander.expand(db, loc.krate, &macro_arg.0)
+    let attr_arg = match &loc.kind {
+        MacroCallKind::Attr { attr_args, .. } => Some(attr_args),
+        _ => None,
+    };
+
+    expander.expand(db, loc.krate, &macro_arg.0, attr_arg)
 }
 
 fn is_self_replicating(from: &SyntaxNode, to: &SyntaxNode) -> bool {
diff --git a/crates/hir_expand/src/eager.rs b/crates/hir_expand/src/eager.rs
index 14af628a1..584ddcf9f 100644
--- a/crates/hir_expand/src/eager.rs
+++ b/crates/hir_expand/src/eager.rs
@@ -17,7 +17,7 @@
 //! > and we need to live with it because it's available on stable and widely relied upon.
 //!
 //!
-//! See the full discussion : https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/Eager.20expansion.20of.20built-in.20macros
+//! See the full discussion : <https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/Eager.20expansion.20of.20built-in.20macros>
 
 use crate::{
     ast::{self, AstNode},
@@ -128,7 +128,7 @@ pub fn expand_eager_macro(
         }),
         kind: MacroCallKind::FnLike { ast_id: call_id, fragment: FragmentKind::Expr },
     });
-    let arg_file_id: MacroCallId = arg_id.into();
+    let arg_file_id: MacroCallId = arg_id;
 
     let parsed_args =
         diagnostic_sink.result(mbe::token_tree_to_syntax_node(&parsed_args, FragmentKind::Expr))?.0;
@@ -177,13 +177,11 @@ fn lazy_expand(
     let ast_id = db.ast_id_map(macro_call.file_id).ast_id(&macro_call.value);
 
     let fragment = crate::to_fragment_kind(&macro_call.value);
-    let id: MacroCallId = def
-        .as_lazy_macro(
-            db,
-            krate,
-            MacroCallKind::FnLike { ast_id: macro_call.with_value(ast_id), fragment },
-        )
-        .into();
+    let id: MacroCallId = def.as_lazy_macro(
+        db,
+        krate,
+        MacroCallKind::FnLike { ast_id: macro_call.with_value(ast_id), fragment },
+    );
 
     let err = db.macro_expand_error(id);
     let value = db.parse_or_expand(id.as_file()).map(|node| InFile::new(id.as_file(), node));
@@ -216,14 +214,14 @@ fn eager_macro_recur(
                     def,
                     macro_resolver,
                     diagnostic_sink,
-                )?
-                .into();
+                )?;
                 db.parse_or_expand(id.as_file())
                     .expect("successful macro expansion should be parseable")
                     .clone_for_update()
             }
             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/input.rs b/crates/hir_expand/src/input.rs
index fe4790e7b..bc3ecc593 100644
--- a/crates/hir_expand/src/input.rs
+++ b/crates/hir_expand/src/input.rs
@@ -1,7 +1,7 @@
 //! Macro input conditioning.
 
 use syntax::{
-    ast::{self, AttrsOwner},
+    ast::{self, make, AttrsOwner},
     AstNode, SyntaxNode,
 };
 
@@ -28,6 +28,14 @@ pub(crate) fn process_macro_input(
 
             remove_derives_up_to(item, derive_attr_index as usize).syntax().clone()
         }
+        MacroCallKind::Attr { invoc_attr_index, .. } => {
+            let item = match ast::Item::cast(node.clone()) {
+                Some(item) => item,
+                None => return node,
+            };
+
+            remove_attr_invoc(item, invoc_attr_index as usize).syntax().clone()
+        }
     }
 }
 
@@ -46,6 +54,19 @@ fn remove_derives_up_to(item: ast::Item, attr_index: usize) -> ast::Item {
     item
 }
 
+/// Removes the attribute invoking an attribute macro from `item`.
+fn remove_attr_invoc(item: ast::Item, attr_index: usize) -> ast::Item {
+    let item = item.clone_for_update();
+    let attr = item
+        .attrs()
+        .nth(attr_index)
+        .unwrap_or_else(|| panic!("cannot find attribute #{}", attr_index));
+    let syntax_index = attr.syntax().index();
+    let ws = make::tokens::whitespace(&" ".repeat(u32::from(attr.syntax().text().len()) as usize));
+    item.syntax().splice_children(syntax_index..syntax_index + 1, vec![ws.into()]);
+    item
+}
+
 #[cfg(test)]
 mod tests {
     use base_db::fixture::WithFixture;
@@ -57,7 +78,7 @@ mod tests {
     use super::*;
 
     fn test_remove_derives_up_to(attr: usize, ra_fixture: &str, expect: Expect) {
-        let (db, file_id) = TestDB::with_single_file(&ra_fixture);
+        let (db, file_id) = TestDB::with_single_file(ra_fixture);
         let parsed = db.parse(file_id);
 
         let mut items: Vec<_> =
diff --git a/crates/hir_expand/src/lib.rs b/crates/hir_expand/src/lib.rs
index 90d8ae240..33107aa24 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;
@@ -51,7 +53,7 @@ mod test_db;
 /// this is a recursive definition! However, the size_of of `HirFileId` is
 /// finite (because everything bottoms out at the real `FileId`) and small
 /// (`MacroCallId` uses the location interning. You can check details here:
-/// https://en.wikipedia.org/wiki/String_interning).
+/// <https://en.wikipedia.org/wiki/String_interning>).
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub struct HirFileId(HirFileIdRepr);
 
@@ -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>),
@@ -258,14 +262,29 @@ pub enum MacroCallKind {
         /// out-of-line modules, which may have attributes spread across 2 files!
         derive_attr_index: u32,
     },
+    Attr {
+        ast_id: AstId<ast::Item>,
+        attr_name: String,
+        attr_args: tt::Subtree,
+        /// Syntactical index of the invoking `#[attribute]`.
+        ///
+        /// Outer attributes are counted first, then inner attributes. This does not support
+        /// out-of-line modules, which may have attributes spread across 2 files!
+        invoc_attr_index: u32,
+    },
 }
 
+// FIXME: attribute indices do not account for `cfg_attr`, which means that we'll strip the whole
+// `cfg_attr` instead of just one of the attributes it expands to
+
 impl MacroCallKind {
     /// Returns the file containing the macro invocation.
     fn file_id(&self) -> HirFileId {
         match self {
             MacroCallKind::FnLike { ast_id, .. } => ast_id.file_id,
-            MacroCallKind::Derive { ast_id, .. } => ast_id.file_id,
+            MacroCallKind::Derive { ast_id, .. } | MacroCallKind::Attr { ast_id, .. } => {
+                ast_id.file_id
+            }
         }
     }
 
@@ -274,7 +293,7 @@ impl MacroCallKind {
             MacroCallKind::FnLike { ast_id, .. } => {
                 ast_id.with_value(ast_id.to_node(db).syntax().clone())
             }
-            MacroCallKind::Derive { ast_id, .. } => {
+            MacroCallKind::Derive { ast_id, .. } | MacroCallKind::Attr { ast_id, .. } => {
                 ast_id.with_value(ast_id.to_node(db).syntax().clone())
             }
         }
@@ -285,7 +304,9 @@ impl MacroCallKind {
             MacroCallKind::FnLike { ast_id, .. } => {
                 Some(ast_id.to_node(db).token_tree()?.syntax().clone())
             }
-            MacroCallKind::Derive { ast_id, .. } => Some(ast_id.to_node(db).syntax().clone()),
+            MacroCallKind::Derive { ast_id, .. } | MacroCallKind::Attr { ast_id, .. } => {
+                Some(ast_id.to_node(db).syntax().clone())
+            }
         }
     }
 
@@ -293,6 +314,7 @@ impl MacroCallKind {
         match self {
             MacroCallKind::FnLike { fragment, .. } => *fragment,
             MacroCallKind::Derive { .. } => FragmentKind::Items,
+            MacroCallKind::Attr { .. } => FragmentKind::Items, // is this always correct?
         }
     }
 }
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/hir_expand/src/proc_macro.rs b/crates/hir_expand/src/proc_macro.rs
index d5643393a..025e10239 100644
--- a/crates/hir_expand/src/proc_macro.rs
+++ b/crates/hir_expand/src/proc_macro.rs
@@ -28,11 +28,16 @@ impl ProcMacroExpander {
         Self { krate, proc_macro_id: None }
     }
 
+    pub fn is_dummy(&self) -> bool {
+        self.proc_macro_id.is_none()
+    }
+
     pub fn expand(
         self,
         db: &dyn AstDatabase,
         calling_crate: CrateId,
         tt: &tt::Subtree,
+        attr_arg: Option<&tt::Subtree>,
     ) -> Result<tt::Subtree, mbe::ExpandError> {
         match self.proc_macro_id {
             Some(id) => {
@@ -40,13 +45,12 @@ impl ProcMacroExpander {
                 let proc_macro = krate_graph[self.krate]
                     .proc_macro
                     .get(id.0 as usize)
-                    .clone()
                     .ok_or_else(|| err!("No derive macro found."))?;
 
                 // Proc macros have access to the environment variables of the invoking crate.
                 let env = &krate_graph[calling_crate].env;
 
-                proc_macro.expander.expand(&tt, None, &env).map_err(mbe::ExpandError::from)
+                proc_macro.expander.expand(tt, attr_arg, env).map_err(mbe::ExpandError::from)
             }
             None => Err(mbe::ExpandError::UnresolvedProcMacro),
         }