3 files changed, 22 insertions, 17 deletions
diff --git a/src/libsyntax/ext/tt/macro_rules.rs b/src/libsyntax/ext/tt/macro_rules.rs
index 728b3e4076d..9162a582599 100644
--- a/src/libsyntax/ext/tt/macro_rules.rs
+++ b/src/libsyntax/ext/tt/macro_rules.rs
@@ -26,7 +26,6 @@ use parse::token::Token::*;
 use symbol::Symbol;
 use tokenstream::{TokenStream, TokenTree};
 
-use std::cell::RefCell;
 use std::collections::HashMap;
 use std::collections::hash_map::Entry;
 
@@ -184,7 +183,7 @@ fn generic_extension<'cx>(cx: &'cx mut ExtCtxt,
 // Holy self-referential!
 
 /// Converts a `macro_rules!` invocation into a syntax extension.
-pub fn compile(sess: &ParseSess, features: &RefCell<Features>, def: &ast::Item) -> SyntaxExtension {
+pub fn compile(sess: &ParseSess, features: &Features, def: &ast::Item) -> SyntaxExtension {
     let lhs_nm = ast::Ident::with_empty_ctxt(Symbol::gensym("lhs"));
     let rhs_nm = ast::Ident::with_empty_ctxt(Symbol::gensym("rhs"));
 
@@ -296,7 +295,7 @@ pub fn compile(sess: &ParseSess, features: &RefCell<Features>, def: &ast::Item)
 }
 
 fn check_lhs_nt_follows(sess: &ParseSess,
-                        features: &RefCell<Features>,
+                        features: &Features,
                         attrs: &[ast::Attribute],
                         lhs: &quoted::TokenTree) -> bool {
     // lhs is going to be like TokenTree::Delimited(...), where the
@@ -353,7 +352,7 @@ fn check_rhs(sess: &ParseSess, rhs: &quoted::TokenTree) -> bool {
 }
 
 fn check_matcher(sess: &ParseSess,
-                 features: &RefCell<Features>,
+                 features: &Features,
                  attrs: &[ast::Attribute],
                  matcher: &[quoted::TokenTree]) -> bool {
     let first_sets = FirstSets::new(matcher);
@@ -601,7 +600,7 @@ impl TokenSet {
 // Requires that `first_sets` is pre-computed for `matcher`;
 // see `FirstSets::new`.
 fn check_matcher_core(sess: &ParseSess,
-                      features: &RefCell<Features>,
+                      features: &Features,
                       attrs: &[ast::Attribute],
                       first_sets: &FirstSets,
                       matcher: &[quoted::TokenTree],
@@ -869,7 +868,7 @@ fn is_in_follow(tok: &quoted::TokenTree, frag: &str) -> Result<bool, (String, &'
 }
 
 fn has_legal_fragment_specifier(sess: &ParseSess,
-                                features: &RefCell<Features>,
+                                features: &Features,
                                 attrs: &[ast::Attribute],
                                 tok: &quoted::TokenTree) -> Result<(), String> {
     debug!("has_legal_fragment_specifier({:?})", tok);
@@ -884,7 +883,7 @@ fn has_legal_fragment_specifier(sess: &ParseSess,
 }
 
 fn is_legal_fragment_specifier(sess: &ParseSess,
-                               features: &RefCell<Features>,
+                               features: &Features,
                                attrs: &[ast::Attribute],
                                frag_name: &str,
                                frag_span: Span) -> bool {
@@ -892,7 +891,7 @@ fn is_legal_fragment_specifier(sess: &ParseSess,
         "item" | "block" | "stmt" | "expr" | "pat" |
         "path" | "ty" | "ident" | "meta" | "tt" | "" => true,
         "lifetime" => {
-            if !features.borrow().macro_lifetime_matcher &&
+            if !features.macro_lifetime_matcher &&
                !attr::contains_name(attrs, "allow_internal_unstable") {
                 let explain = feature_gate::EXPLAIN_LIFETIME_MATCHER;
                 emit_feature_err(sess,
@@ -904,7 +903,7 @@ fn is_legal_fragment_specifier(sess: &ParseSess,
             true
         },
         "vis" => {
-            if !features.borrow().macro_vis_matcher &&
+            if !features.macro_vis_matcher &&
                !attr::contains_name(attrs, "allow_internal_unstable") {
                 let explain = feature_gate::EXPLAIN_VIS_MATCHER;
                 emit_feature_err(sess,
diff --git a/src/libsyntax/ext/tt/quoted.rs b/src/libsyntax/ext/tt/quoted.rs
index c9d7f78c2e3..122bb9ba024 100644
--- a/src/libsyntax/ext/tt/quoted.rs
+++ b/src/libsyntax/ext/tt/quoted.rs
@@ -17,7 +17,6 @@ use symbol::keywords;
 use syntax_pos::{BytePos, Span, DUMMY_SP};
 use tokenstream;
 
-use std::cell::RefCell;
 use std::iter::Peekable;
 use rustc_data_structures::sync::Lrc;
 
@@ -183,7 +182,7 @@ pub fn parse(
     input: tokenstream::TokenStream,
     expect_matchers: bool,
     sess: &ParseSess,
-    features: &RefCell<Features>,
+    features: &Features,
     attrs: &[ast::Attribute],
 ) -> Vec<TokenTree> {
     // Will contain the final collection of `self::TokenTree`
@@ -251,7 +250,7 @@ fn parse_tree<I>(
     trees: &mut Peekable<I>,
     expect_matchers: bool,
     sess: &ParseSess,
-    features: &RefCell<Features>,
+    features: &Features,
     attrs: &[ast::Attribute],
 ) -> TokenTree
 where
@@ -382,7 +381,7 @@ fn parse_sep_and_kleene_op<I>(
     input: &mut Peekable<I>,
     span: Span,
     sess: &ParseSess,
-    features: &RefCell<Features>,
+    features: &Features,
     attrs: &[ast::Attribute],
 ) -> (Option<token::Token>, KleeneOp)
 where
@@ -415,7 +414,7 @@ where
                 match parse_kleene_op(input, span) {
                     // #2 is a KleeneOp (this is the only valid option) :)
                     Ok(Ok(op)) if op == KleeneOp::ZeroOrOne => {
-                        if !features.borrow().macro_at_most_once_rep
+                        if !features.macro_at_most_once_rep
                             && !attr::contains_name(attrs, "allow_internal_unstable")
                         {
                             let explain = feature_gate::EXPLAIN_MACRO_AT_MOST_ONCE_REP;
@@ -438,7 +437,7 @@ where
                     Err(span) => span,
                 }
             } else {
-                if !features.borrow().macro_at_most_once_rep
+                if !features.macro_at_most_once_rep
                     && !attr::contains_name(attrs, "allow_internal_unstable")
                 {
                     let explain = feature_gate::EXPLAIN_MACRO_AT_MOST_ONCE_REP;
@@ -460,7 +459,7 @@ where
         Ok(Err((tok, span))) => match parse_kleene_op(input, span) {
             // #2 is a KleeneOp :D
             Ok(Ok(op)) if op == KleeneOp::ZeroOrOne => {
-                if !features.borrow().macro_at_most_once_rep
+                if !features.macro_at_most_once_rep
                     && !attr::contains_name(attrs, "allow_internal_unstable")
                 {
                     let explain = feature_gate::EXPLAIN_MACRO_AT_MOST_ONCE_REP;
@@ -487,7 +486,7 @@ where
         Err(span) => span,
     };
 
-    if !features.borrow().macro_at_most_once_rep
+    if !features.macro_at_most_once_rep
         && !attr::contains_name(attrs, "allow_internal_unstable")
     {
         sess.span_diagnostic
diff --git a/src/libsyntax/feature_gate.rs b/src/libsyntax/feature_gate.rs
index 058df1d5169..45d82bc7af3 100644
--- a/src/libsyntax/feature_gate.rs
+++ b/src/libsyntax/feature_gate.rs
@@ -62,6 +62,7 @@ macro_rules! declare_features {
             &[$((stringify!($feature), $ver, $issue, set!($feature))),+];
 
         /// A set of features to be used by later passes.
+        #[derive(Clone)]
         pub struct Features {
             /// `#![feature]` attrs for stable language features, for error reporting
             pub declared_stable_lang_features: Vec<(Symbol, Span)>,
@@ -78,6 +79,12 @@ macro_rules! declare_features {
                     $($feature: false),+
                 }
             }
+
+            pub fn walk_feature_fields<F>(&self, mut f: F)
+                where F: FnMut(&str, bool)
+            {
+                $(f(stringify!($feature), self.$feature);)+
+            }
         }
     };