Retry failed macro matching for diagnostics

compiler/rustc_expand/src/mbe/macro_parser.rs

@@ -72,6 +72,7 @@
 
 pub(crate) use NamedMatch::*;
 pub(crate) use ParseResult::*;
+use rustc_errors::ErrorGuaranteed;
 
 use crate::mbe::{KleeneOp, TokenTree};
 
@@ -270,7 +271,7 @@ pub(crate) enum ParseResult<T> {
     Failure(Token, &'static str),
     /// Fatal error (malformed macro?). Abort compilation.
     Error(rustc_span::Span, String),
-    ErrorReported,
+    ErrorReported(ErrorGuaranteed),
 }
 
 /// A `ParseResult` where the `Success` variant contains a mapping of
@@ -450,7 +451,7 @@ impl TtParser {
                         // Try zero matches of this sequence, by skipping over it.
                         self.cur_mps.push(MatcherPos {
                             idx: idx_first_after,
-                            matches: mp.matches.clone(), // a cheap clone
+                            matches: Lrc::clone(&mp.matches),
                         });
                     }
 
@@ -463,8 +464,8 @@ impl TtParser {
                     // sequence. If that's not possible, `ending_mp` will fail quietly when it is
                     // processed next time around the loop.
                     let ending_mp = MatcherPos {
-                        idx: mp.idx + 1,             // +1 skips the Kleene op
-                        matches: mp.matches.clone(), // a cheap clone
+                        idx: mp.idx + 1, // +1 skips the Kleene op
+                        matches: Lrc::clone(&mp.matches),
                     };
                     self.cur_mps.push(ending_mp);
 
@@ -479,8 +480,8 @@ impl TtParser {
                     // separator yet. Try ending the sequence. If that's not possible, `ending_mp`
                     // will fail quietly when it is processed next time around the loop.
                     let ending_mp = MatcherPos {
-                        idx: mp.idx + 2,             // +2 skips the separator and the Kleene op
-                        matches: mp.matches.clone(), // a cheap clone
+                        idx: mp.idx + 2, // +2 skips the separator and the Kleene op
+                        matches: Lrc::clone(&mp.matches),
                     };
                     self.cur_mps.push(ending_mp);
 
@@ -612,14 +613,14 @@ impl TtParser {
                         // edition-specific matching behavior for non-terminals.
                         let nt = match parser.to_mut().parse_nonterminal(kind) {
                             Err(mut err) => {
-                                err.span_label(
+                                let guarantee = err.span_label(
                                     span,
                                     format!(
                                         "while parsing argument for this `{kind}` macro fragment"
                                     ),
                                 )
                                 .emit();
-                                return ErrorReported;
+                                return ErrorReported(guarantee);
                             }
                             Ok(nt) => nt,
                         };

compiler/rustc_expand/src/mbe/macro_rules.rs

@@ -333,7 +333,7 @@ fn expand_macro<'cx>(
                 cx.struct_span_err(span, &msg).emit();
                 return DummyResult::any(span);
             }
-            ErrorReported => return DummyResult::any(sp),
+            ErrorReported(_) => return DummyResult::any(sp),
         }
 
         // The matcher was not `Success(..)`ful.
@@ -470,7 +470,7 @@ pub fn compile_declarative_macro(
                 .emit();
             return dummy_syn_ext();
         }
-        ErrorReported => {
+        ErrorReported(_) => {
             return dummy_syn_ext();
         }
     };