Replace a lock with an atomic

compiler/rustc_parse/src/parser/mod.rs

@@ -29,6 +29,7 @@
 use rustc_ast::{HasAttrs, HasTokens, Unsafe, Visibility, VisibilityKind};
 use rustc_ast_pretty::pprust;
 use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::sync::Ordering;
 use rustc_errors::PResult;
 use rustc_errors::{
     Applicability, DiagnosticBuilder, ErrorGuaranteed, FatalError, IntoDiagnostic, MultiSpan,
@@ -1540,8 +1541,12 @@ pub(crate) fn make_unclosed_delims_error(
 }
 
 pub fn emit_unclosed_delims(unclosed_delims: &mut Vec<UnmatchedDelim>, sess: &ParseSess) {
-    *sess.reached_eof.borrow_mut() |=
-        unclosed_delims.iter().any(|unmatched_delim| unmatched_delim.found_delim.is_none());
+    let _ = sess.reached_eof.compare_exchange(
+        false,
+        unclosed_delims.iter().any(|unmatched_delim| unmatched_delim.found_delim.is_none()),
+        Ordering::Relaxed,
+        Ordering::Relaxed,
+    );
     for unmatched in unclosed_delims.drain(..) {
         if let Some(mut e) = make_unclosed_delims_error(unmatched, sess) {
             e.emit();

compiler/rustc_passes/src/entry.rs

@@ -187,7 +187,7 @@ fn sigpipe(tcx: TyCtxt<'_>, def_id: DefId) -> u8 {
 
 fn no_main_err(tcx: TyCtxt<'_>, visitor: &EntryContext<'_>) {
     let sp = tcx.def_span(CRATE_DEF_ID);
-    if *tcx.sess.parse_sess.reached_eof.borrow() {
+    if tcx.sess.parse_sess.reached_eof.load(rustc_data_structures::sync::Ordering::Relaxed) {
         // There's an unclosed brace that made the parser reach `Eof`, we shouldn't complain about
         // the missing `fn main()` then as it might have been hidden inside an unclosed block.
         tcx.sess.delay_span_bug(sp, "`main` not found, but expected unclosed brace error");

compiler/rustc_session/src/parse.rs

@@ -8,7 +8,7 @@
 };
 use rustc_ast::node_id::NodeId;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
-use rustc_data_structures::sync::{Lock, Lrc};
+use rustc_data_structures::sync::{AtomicBool, Lock, Lrc};
 use rustc_errors::{emitter::SilentEmitter, ColorConfig, Handler};
 use rustc_errors::{
     fallback_fluent_bundle, Diagnostic, DiagnosticBuilder, DiagnosticId, DiagnosticMessage,
@@ -208,7 +208,7 @@ pub struct ParseSess {
     pub gated_spans: GatedSpans,
     pub symbol_gallery: SymbolGallery,
     /// The parser has reached `Eof` due to an unclosed brace. Used to silence unnecessary errors.
-    pub reached_eof: Lock<bool>,
+    pub reached_eof: AtomicBool,
     /// Environment variables accessed during the build and their values when they exist.
     pub env_depinfo: Lock<FxHashSet<(Symbol, Option<Symbol>)>>,
     /// File paths accessed during the build.
@@ -254,7 +254,7 @@ pub fn with_span_handler(handler: Handler, source_map: Lrc<SourceMap>) -> Self {
             ambiguous_block_expr_parse: Lock::new(FxHashMap::default()),
             gated_spans: GatedSpans::default(),
             symbol_gallery: SymbolGallery::default(),
-            reached_eof: Lock::new(false),
+            reached_eof: AtomicBool::new(false),
             env_depinfo: Default::default(),
             file_depinfo: Default::default(),
             type_ascription_path_suggestions: Default::default(),