parser: macro_rules is a weak keyword

src/librustc_expand/mbe/macro_check.rs

@@ -109,7 +109,7 @@ use crate::mbe::{KleeneToken, TokenTree};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_session::lint::builtin::META_VARIABLE_MISUSE;
 use rustc_session::parse::ParseSess;
-use rustc_span::symbol::{kw, sym};
+use rustc_span::symbol::kw;
 use rustc_span::{symbol::Ident, MultiSpan, Span};
 use syntax::ast::NodeId;
 use syntax::token::{DelimToken, Token, TokenKind};
@@ -392,7 +392,7 @@ fn check_nested_occurrences(
                 NestedMacroState::Empty,
                 &TokenTree::Token(Token { kind: TokenKind::Ident(name, false), .. }),
             ) => {
-                if name == sym::macro_rules {
+                if name == kw::MacroRules {
                     state = NestedMacroState::MacroRules;
                 } else if name == kw::Macro {
                     state = NestedMacroState::Macro;

src/librustc_expand/parse/tests.rs

@@ -65,7 +65,7 @@ fn string_to_tts_macro() {
 
         match tts {
             [TokenTree::Token(Token { kind: token::Ident(name_macro_rules, false), .. }), TokenTree::Token(Token { kind: token::Not, .. }), TokenTree::Token(Token { kind: token::Ident(name_zip, false), .. }), TokenTree::Delimited(_, macro_delim, macro_tts)]
-                if name_macro_rules == &sym::macro_rules && name_zip.as_str() == "zip" =>
+                if name_macro_rules == &kw::MacroRules && name_zip.as_str() == "zip" =>
             {
                 let tts = &macro_tts.trees().collect::<Vec<_>>();
                 match &tts[..] {

src/librustc_parse/parser/item.rs

@@ -1343,14 +1343,14 @@ impl<'a> Parser<'a> {
 
     /// Is this unambiguously the start of a `macro_rules! foo` item defnition?
     fn is_macro_rules_item(&mut self) -> bool {
-        self.check_keyword(sym::macro_rules)
+        self.check_keyword(kw::MacroRules)
             && self.look_ahead(1, |t| *t == token::Not)
             && self.look_ahead(2, |t| t.is_ident())
     }
 
     /// Parses a legacy `macro_rules! foo { ... }` declarative macro.
     fn parse_item_macro_rules(&mut self, vis: &Visibility) -> PResult<'a, ItemInfo> {
-        self.expect_keyword(sym::macro_rules)?; // `macro_rules`
+        self.expect_keyword(kw::MacroRules)?; // `macro_rules`
         self.expect(&token::Not)?; // `!`
 
         let ident = self.parse_ident()?;

src/librustc_span/symbol.rs

@@ -97,6 +97,7 @@ symbols! {
         Auto:               "auto",
         Catch:              "catch",
         Default:            "default",
+        MacroRules:         "macro_rules",
         Raw:                "raw",
         Union:              "union",
     }
@@ -429,7 +430,6 @@ symbols! {
         macro_lifetime_matcher,
         macro_literal_matcher,
         macro_reexport,
-        macro_rules,
         macros_in_extern,
         macro_use,
         macro_vis_matcher,
@@ -1071,6 +1071,9 @@ pub mod sym {
 
     symbols!();
 
+    // Used from a macro in `librustc_feature/accepted.rs`
+    pub use super::kw::MacroRules as macro_rules;
+
     // Get the symbol for an integer. The first few non-negative integers each
     // have a static symbol and therefore are fast.
     pub fn integer<N: TryInto<usize> + Copy + ToString>(n: N) -> Symbol {