Only bump error count when we are sure that the diagnostic is not a repetition.

This ensures that if we emit the same diagnostic twice, the error count will
match the real number of errors shown to the user.

Fixes #42106

1 files changed, 3 insertions, 0 deletions

diff --git a/src/librustc_errors/lib.rs b/src/librustc_errors/lib.rs
index 2ac49958d3c..c4db39fae86 100644
--- a/src/librustc_errors/lib.rs
+++ b/src/librustc_errors/lib.rs
@@ -588,6 +588,9 @@ impl Handler {
         // one:
         if self.emitted_diagnostics.borrow_mut().insert(diagnostic_hash) {
             self.emitter.borrow_mut().emit(db);
+            if db.is_error() {
+                self.bump_err_count();
+            }
         }
     }
 }