Change the calling conventions for handleUnrecoverableError.

pkg/front_end/lib/src/fasta/kernel/body_builder.dart

Index: pkg/front_end/lib/src/fasta/kernel/body_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
index afcabb0fc779ff76d2fb69b8955a7aab78951566..61c0754402d4f69e2d48b99c11c5451ba56c60fb 100644
--- a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
@@ -2199,7 +2199,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
         arguments.putIfAbsent("actual", () => token.value);
         handleRecoverableError(token, ErrorKind.ExpectedButGot, arguments);
       }
-      return token;
+      return newSyntheticToken(token);
     }
     return super.handleUnrecoverableError(token, kind, arguments);
   }