improve fasta parser export declaration recovery

pkg/analyzer/lib/src/fasta/ast_builder.dart

Index: pkg/analyzer/lib/src/fasta/ast_builder.dart
diff --git a/pkg/analyzer/lib/src/fasta/ast_builder.dart b/pkg/analyzer/lib/src/fasta/ast_builder.dart
index b3896c96a8727f1d38e1b56e7093a83ddf815c77..c2a17360544cc6417422eec39b4911b122e918d6 100644
--- a/pkg/analyzer/lib/src/fasta/ast_builder.dart
+++ b/pkg/analyzer/lib/src/fasta/ast_builder.dart
@@ -1928,6 +1928,10 @@ class AstBuilder extends ScopeListener {
         errorReporter?.reportErrorForOffset(
             ParserErrorCode.EXPECTED_TYPE_NAME, message.charOffset, 1);
         return;
+      case "EXPECTED_STRING_LITERAL":
+        errorReporter?.reportErrorForOffset(
+            ParserErrorCode.EXPECTED_STRING_LITERAL, message.charOffset, 1);
+        return;
       default:
       // fall through
     }