Rollup merge of #95808 - petrochenkov:fragspec, r=nnethercote

expand: Remove `ParseSess::missing_fragment_specifiers`

It was used for deduplicating some errors for legacy code which are mostly deduplicated even without that, but at cost of global mutable state, which is not a good tradeoff.

cc https://github.com/rust-lang/rust/pull/95747#issuecomment-1091619403
r? ``@nnethercote``

compiler/rustc_expand/src/mbe/macro_check.rs

@@ -110,7 +110,7 @@ use rustc_ast::token::{DelimToken, Token, TokenKind};
 use rustc_ast::{NodeId, DUMMY_NODE_ID};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::MultiSpan;
-use rustc_session::lint::builtin::META_VARIABLE_MISUSE;
+use rustc_session::lint::builtin::{META_VARIABLE_MISUSE, MISSING_FRAGMENT_SPECIFIER};
 use rustc_session::parse::ParseSess;
 use rustc_span::symbol::kw;
 use rustc_span::{symbol::MacroRulesNormalizedIdent, Span};
@@ -261,7 +261,18 @@ fn check_binders(
             }
         }
         // Similarly, this can only happen when checking a toplevel macro.
-        TokenTree::MetaVarDecl(span, name, _kind) => {
+        TokenTree::MetaVarDecl(span, name, kind) => {
+            if kind.is_none() && node_id != DUMMY_NODE_ID {
+                // FIXME: Report this as a hard error eventually and remove equivalent errors from
+                // `parse_tt_inner` and `nameize`. Until then the error may be reported twice, once
+                // as a hard error and then once as a buffered lint.
+                sess.buffer_lint(
+                    MISSING_FRAGMENT_SPECIFIER,
+                    span,
+                    node_id,
+                    &format!("missing fragment specifier"),
+                );
+            }
             if !macros.is_empty() {
                 sess.span_diagnostic.span_bug(span, "unexpected MetaVarDecl in nested lhs");
             }

compiler/rustc_expand/src/mbe/macro_parser.rs

@@ -411,7 +411,6 @@ impl TtParser {
     /// track of through the mps generated.
     fn parse_tt_inner(
         &mut self,
-        sess: &ParseSess,
         matcher: &[MatcherLoc],
         token: &Token,
     ) -> Option<NamedParseResult> {
@@ -519,11 +518,9 @@ impl TtParser {
                             self.bb_mps.push(mp);
                         }
                     } else {
+                        // E.g. `$e` instead of `$e:expr`, reported as a hard error if actually used.
                         // Both this check and the one in `nameize` are necessary, surprisingly.
-                        if sess.missing_fragment_specifiers.borrow_mut().remove(&span).is_some() {
-                            // E.g. `$e` instead of `$e:expr`.
-                            return Some(Error(span, "missing fragment specifier".to_string()));
-                        }
+                        return Some(Error(span, "missing fragment specifier".to_string()));
                     }
                 }
                 MatcherLoc::Eof => {
@@ -549,7 +546,7 @@ impl TtParser {
                     // Need to take ownership of the matches from within the `Lrc`.
                     Lrc::make_mut(&mut eof_mp.matches);
                     let matches = Lrc::try_unwrap(eof_mp.matches).unwrap().into_iter();
-                    self.nameize(sess, matcher, matches)
+                    self.nameize(matcher, matches)
                 }
                 EofMatcherPositions::Multiple => {
                     Error(token.span, "ambiguity: multiple successful parses".to_string())
@@ -587,7 +584,7 @@ impl TtParser {
 
             // Process `cur_mps` until either we have finished the input or we need to get some
             // parsing from the black-box parser done.
-            if let Some(res) = self.parse_tt_inner(&parser.sess, matcher, &parser.token) {
+            if let Some(res) = self.parse_tt_inner(matcher, &parser.token) {
                 return res;
             }
 
@@ -694,7 +691,6 @@ impl TtParser {
 
     fn nameize<I: Iterator<Item = NamedMatch>>(
         &self,
-        sess: &ParseSess,
         matcher: &[MatcherLoc],
         mut res: I,
     ) -> NamedParseResult {
@@ -711,11 +707,9 @@ impl TtParser {
                         }
                     };
                 } else {
+                    // E.g. `$e` instead of `$e:expr`, reported as a hard error if actually used.
                     // Both this check and the one in `parse_tt_inner` are necessary, surprisingly.
-                    if sess.missing_fragment_specifiers.borrow_mut().remove(&span).is_some() {
-                        // E.g. `$e` instead of `$e:expr`.
-                        return Error(span, "missing fragment specifier".to_string());
-                    }
+                    return Error(span, "missing fragment specifier".to_string());
                 }
             }
         }

compiler/rustc_expand/src/mbe/quoted.rs

@@ -2,8 +2,7 @@ use crate::mbe::macro_parser::count_metavar_decls;
 use crate::mbe::{Delimited, KleeneOp, KleeneToken, MetaVarExpr, SequenceRepetition, TokenTree};
 
 use rustc_ast::token::{self, Token};
-use rustc_ast::tokenstream;
-use rustc_ast::{NodeId, DUMMY_NODE_ID};
+use rustc_ast::{tokenstream, NodeId};
 use rustc_ast_pretty::pprust;
 use rustc_feature::Features;
 use rustc_session::parse::{feature_err, ParseSess};
@@ -104,10 +103,7 @@ pub(super) fn parse(
                     }
                     tree => tree.as_ref().map_or(start_sp, tokenstream::TokenTree::span),
                 };
-                if node_id != DUMMY_NODE_ID {
-                    // Macros loaded from other crates have dummy node ids.
-                    sess.missing_fragment_specifiers.borrow_mut().insert(span, node_id);
-                }
+
                 result.push(TokenTree::MetaVarDecl(span, ident, None));
             }