This will work in most cases, but there is an edge case:

$ bin/opal -e 'loop(&-> { return })'

/tmp/opal-system-runner20231004-47362-rqbq0f.js:5473
        } else { throw $err; }
                 ^
{
  '$thrower_type': 'return',
  '$throw': [Function: $throw],
  is_orphan: false,
  '$v': klass {
    '$$id': 4,
    apply: [Function (anonymous)],
    call: [Function (anonymous)],
    '$$frozen': true,
    '$$comparable': false
  }
}

Actually this problem was there (for all yield calls) until v1.8.0.alpha1 and fixed in #2591.

Thanks for the heads up! In fact, when doing the closure tracking part, I ensured that such an expression would simply compile to return nil, I guess I will have to revisit that part.

This can be fixed by Proc#call.
However, considering there are many block() calls in corelib codes, maybe it's better to make lambda function handle the thrower by itself rather than fixing this patch.