Report fatal lexer errors in `--cfg` command line arguments

1 files changed, 17 insertions, 4 deletions

diff --git a/compiler/rustc_errors/src/emitter.rs b/compiler/rustc_errors/src/emitter.rs
index 29f352ae585..fa986ce8a7e 100644
--- a/compiler/rustc_errors/src/emitter.rs
+++ b/compiler/rustc_errors/src/emitter.rs
@@ -15,7 +15,7 @@ use rustc_span::{MultiSpan, SourceFile, Span};
 use crate::snippet::{Annotation, AnnotationType, Line, MultilineAnnotation, Style, StyledString};
 use crate::styled_buffer::StyledBuffer;
 use crate::{
-    CodeSuggestion, Diagnostic, DiagnosticId, Level, SubDiagnostic, SubstitutionHighlight,
+    CodeSuggestion, Diagnostic, DiagnosticId, Handler, Level, SubDiagnostic, SubstitutionHighlight,
     SuggestionStyle,
 };
 
@@ -527,14 +527,27 @@ impl Emitter for EmitterWriter {
     }
 }
 
-/// An emitter that does nothing when emitting a diagnostic.
-pub struct SilentEmitter;
+/// An emitter that does nothing when emitting a non-fatal diagnostic.
+/// Fatal diagnostics are forwarded to `fatal_handler` to avoid silent
+/// failures of rustc, as witnessed e.g. in issue #89358.
+pub struct SilentEmitter {
+    pub fatal_handler: Handler,
+    pub fatal_note: Option<String>,
+}
 
 impl Emitter for SilentEmitter {
     fn source_map(&self) -> Option<&Lrc<SourceMap>> {
         None
     }
-    fn emit_diagnostic(&mut self, _: &Diagnostic) {}
+    fn emit_diagnostic(&mut self, d: &Diagnostic) {
+        if d.level == Level::Fatal {
+            let mut d = d.clone();
+            if let Some(ref note) = self.fatal_note {
+                d.note(note);
+            }
+            self.fatal_handler.emit_diagnostic(&d);
+        }
+    }
 }
 
 /// Maximum number of lines we will print for a multiline suggestion; arbitrary.