Error when interacting with '...': "Promise has already been forced"

I wanted to write a helper function to convert fixed strings into a regex like `${PART1}.*${PART2}.*`; `rex::rex` is a natural choice.

But, doing so fails:

```
combiner <- function(...) paste(sapply(list(...), rex::rex), collapse = ".*")

combiner('a', 'a*b', 'c?d')
# Error in lazyeval::lazy_dots(...) : Promise has already been forced
```

Is that WAI?