Exit when there are unmatched delims to avoid noisy diagnostics

compiler/rustc_parse/src/lib.rs

@@ -204,16 +204,23 @@ pub fn maybe_file_to_stream(
         lexer::parse_token_trees(sess, src.as_str(), source_file.start_pos, override_span);
 
     match token_trees {
-        Ok(stream) => Ok((stream, unmatched_braces)),
-        Err(err) => {
+        Ok(stream) if unmatched_braces.is_empty() => Ok((stream, unmatched_braces)),
+        _ => {
+            // Return error if there are unmatched delimiters or unclosng delimiters.
+            // We emit delimiter mismatch errors first, then emit the unclosing delimiter mismatch
+            // because the delimiter mismatch is more likely to be the root cause of the
+
             let mut buffer = Vec::with_capacity(1);
-            err.buffer(&mut buffer);
             // Not using `emit_unclosed_delims` to use `db.buffer`
             for unmatched in unmatched_braces {
                 if let Some(err) = make_unclosed_delims_error(unmatched, &sess) {
                     err.buffer(&mut buffer);
                 }
             }
+            if let Err(err) = token_trees {
+                // Add unclosing delimiter error
+                err.buffer(&mut buffer);
+            }
             Err(buffer)
         }
     }