Rollup merge of #146137 - Urgau:cfg-disallow-frontmatter, r=fmease

Disallow frontmatter in `--cfg` and `--check-cfg` arguments

This PR disallows the frontmatter syntax in `--cfg` and `--check-cfg` arguments.

Fixes https://github.com/rust-lang/rust/issues/146130
r? fmease

2 files changed, 20 insertions, 6 deletions

diff --git a/compiler/rustc_interface/src/interface.rs b/compiler/rustc_interface/src/interface.rs
index 8f131f45bbd..4c820b8877b 100644
--- a/compiler/rustc_interface/src/interface.rs
+++ b/compiler/rustc_interface/src/interface.rs
@@ -13,7 +13,7 @@ use rustc_lint::LintStore;
 use rustc_middle::ty;
 use rustc_middle::ty::CurrentGcx;
 use rustc_middle::util::Providers;
-use rustc_parse::new_parser_from_source_str;
+use rustc_parse::new_parser_from_simple_source_str;
 use rustc_parse::parser::attr::AllowLeadingUnsafe;
 use rustc_query_impl::QueryCtxt;
 use rustc_query_system::query::print_query_stack;
@@ -68,7 +68,7 @@ pub(crate) fn parse_cfg(dcx: DiagCtxtHandle<'_>, cfgs: Vec<String>) -> Cfg {
                 };
             }
 
-            match new_parser_from_source_str(&psess, filename, s.to_string()) {
+            match new_parser_from_simple_source_str(&psess, filename, s.to_string()) {
                 Ok(mut parser) => match parser.parse_meta_item(AllowLeadingUnsafe::No) {
                     Ok(meta_item) if parser.token == token::Eof => {
                         if meta_item.path.segments.len() != 1 {
@@ -166,7 +166,7 @@ pub(crate) fn parse_check_cfg(dcx: DiagCtxtHandle<'_>, specs: Vec<String>) -> Ch
             error!("expected `cfg(name, values(\"value1\", \"value2\", ... \"valueN\"))`")
         };
 
-        let mut parser = match new_parser_from_source_str(&psess, filename, s.to_string()) {
+        let mut parser = match new_parser_from_simple_source_str(&psess, filename, s.to_string()) {
             Ok(parser) => parser,
             Err(errs) => {
                 errs.into_iter().for_each(|err| err.cancel());
diff --git a/compiler/rustc_parse/src/lib.rs b/compiler/rustc_parse/src/lib.rs
index 197333d942d..b790966acfd 100644
--- a/compiler/rustc_parse/src/lib.rs
+++ b/compiler/rustc_parse/src/lib.rs
@@ -62,7 +62,20 @@ pub fn new_parser_from_source_str(
     source: String,
 ) -> Result<Parser<'_>, Vec<Diag<'_>>> {
     let source_file = psess.source_map().new_source_file(name, source);
-    new_parser_from_source_file(psess, source_file)
+    new_parser_from_source_file(psess, source_file, FrontmatterAllowed::Yes)
+}
+
+/// Creates a new parser from a simple (no frontmatter) source string.
+///
+/// On failure, the errors must be consumed via `unwrap_or_emit_fatal`, `emit`, `cancel`,
+/// etc., otherwise a panic will occur when they are dropped.
+pub fn new_parser_from_simple_source_str(
+    psess: &ParseSess,
+    name: FileName,
+    source: String,
+) -> Result<Parser<'_>, Vec<Diag<'_>>> {
+    let source_file = psess.source_map().new_source_file(name, source);
+    new_parser_from_source_file(psess, source_file, FrontmatterAllowed::No)
 }
 
 /// Creates a new parser from a filename. On failure, the errors must be consumed via
@@ -96,7 +109,7 @@ pub fn new_parser_from_file<'a>(
         }
         err.emit();
     });
-    new_parser_from_source_file(psess, source_file)
+    new_parser_from_source_file(psess, source_file, FrontmatterAllowed::Yes)
 }
 
 pub fn utf8_error<E: EmissionGuarantee>(
@@ -147,9 +160,10 @@ pub fn utf8_error<E: EmissionGuarantee>(
 fn new_parser_from_source_file(
     psess: &ParseSess,
     source_file: Arc<SourceFile>,
+    frontmatter_allowed: FrontmatterAllowed,
 ) -> Result<Parser<'_>, Vec<Diag<'_>>> {
     let end_pos = source_file.end_position();
-    let stream = source_file_to_stream(psess, source_file, None, FrontmatterAllowed::Yes)?;
+    let stream = source_file_to_stream(psess, source_file, None, frontmatter_allowed)?;
     let mut parser = Parser::new(psess, stream, None);
     if parser.token == token::Eof {
         parser.token.span = Span::new(end_pos, end_pos, parser.token.span.ctxt(), None);