resolve: Avoid creating fresh syntax extensions for all non-macro attributes

Author: petrochenkov

src/librustc_resolve/build_reduced_graph.rs

@@ -29,7 +29,7 @@ use syntax::attr;
 
 use syntax::ast::{self, Block, ForeignItem, ForeignItemKind, Item, ItemKind, NodeId};
 use syntax::ast::{MetaItemKind, StmtKind, TraitItem, TraitItemKind, Variant};
-use syntax::ext::base::{MacroKind, SyntaxExtension, SyntaxExtensionKind};
+use syntax::ext::base::{MacroKind, SyntaxExtension};
 use syntax::ext::base::Determinacy::Undetermined;
 use syntax::ext::hygiene::Mark;
 use syntax::ext::tt::macro_rules;
@@ -772,12 +772,8 @@ impl<'a> Resolver<'a> {
     pub fn get_macro(&mut self, res: Res) -> Lrc<SyntaxExtension> {
         let def_id = match res {
             Res::Def(DefKind::Macro(..), def_id) => def_id,
-            Res::NonMacroAttr(attr_kind) => return Lrc::new(SyntaxExtension::default(
-                SyntaxExtensionKind::NonMacroAttr {
-                    mark_used: attr_kind == NonMacroAttrKind::Tool
-                },
-                self.session.edition(),
-            )),
+            Res::NonMacroAttr(attr_kind) =>
+                return self.non_macro_attr(attr_kind == NonMacroAttrKind::Tool),
             _ => panic!("expected `DefKind::Macro` or `Res::NonMacroAttr`"),
         };
         if let Some(ext) = self.macro_map.get(&def_id) {

src/librustc_resolve/lib.rs

@@ -41,7 +41,7 @@ use rustc_metadata::cstore::CStore;
 use syntax::source_map::SourceMap;
 use syntax::ext::hygiene::{Mark, Transparency, SyntaxContext};
 use syntax::ast::{self, Name, NodeId, Ident, FloatTy, IntTy, UintTy};
-use syntax::ext::base::SyntaxExtension;
+use syntax::ext::base::{SyntaxExtension, SyntaxExtensionKind};
 use syntax::ext::base::Determinacy::{self, Determined, Undetermined};
 use syntax::ext::base::MacroKind;
 use syntax::symbol::{Symbol, kw, sym};
@@ -1668,6 +1668,7 @@ pub struct Resolver<'a> {
     macro_use_prelude: FxHashMap<Name, &'a NameBinding<'a>>,
     pub all_macros: FxHashMap<Name, Res>,
     macro_map: FxHashMap<DefId, Lrc<SyntaxExtension>>,
+    non_macro_attrs: [Lrc<SyntaxExtension>; 2],
     macro_defs: FxHashMap<Mark, DefId>,
     local_macro_def_scopes: FxHashMap<NodeId, Module<'a>>,
 
@@ -1941,6 +1942,10 @@ impl<'a> Resolver<'a> {
         let mut macro_defs = FxHashMap::default();
         macro_defs.insert(Mark::root(), root_def_id);
 
+        let non_macro_attr = |mark_used| Lrc::new(SyntaxExtension::default(
+            SyntaxExtensionKind::NonMacroAttr { mark_used }, session.edition()
+        ));
+
         Resolver {
             session,
 
@@ -2014,6 +2019,7 @@ impl<'a> Resolver<'a> {
             macro_use_prelude: FxHashMap::default(),
             all_macros: FxHashMap::default(),
             macro_map: FxHashMap::default(),
+            non_macro_attrs: [non_macro_attr(false), non_macro_attr(true)],
             invocations,
             macro_defs,
             local_macro_def_scopes: FxHashMap::default(),
@@ -2030,6 +2036,10 @@ impl<'a> Resolver<'a> {
         Default::default()
     }
 
+    fn non_macro_attr(&self, mark_used: bool) -> Lrc<SyntaxExtension> {
+        self.non_macro_attrs[mark_used as usize].clone()
+    }
+
     /// Runs the function on each namespace.
     fn per_ns<F: FnMut(&mut Self, Namespace)>(&mut self, mut f: F) {
         f(self, TypeNS);

src/librustc_resolve/macros.rs

@@ -15,7 +15,7 @@ use syntax::ast::{self, Ident};
 use syntax::attr;
 use syntax::errors::DiagnosticBuilder;
 use syntax::ext::base::{self, Determinacy};
-use syntax::ext::base::{MacroKind, SyntaxExtension, SyntaxExtensionKind};
+use syntax::ext::base::{MacroKind, SyntaxExtension};
 use syntax::ext::expand::{AstFragment, Invocation, InvocationKind};
 use syntax::ext::hygiene::Mark;
 use syntax::ext::tt::macro_rules;
@@ -211,8 +211,7 @@ impl<'a> base::Resolver for Resolver<'a> {
             Ok((res, ext)) => (res, ext),
             Err(Determinacy::Determined) if kind == MacroKind::Attr => {
                 // Replace unresolved attributes with used inert attributes for better recovery.
-                let kind = SyntaxExtensionKind::NonMacroAttr { mark_used: true };
-                return Ok(Some(Lrc::new(SyntaxExtension::default(kind, self.session.edition()))));
+                return Ok(Some(self.non_macro_attr(true)));
             }
             Err(determinacy) => return Err(determinacy),
         };