Regular expressions with `rex()` do not work anymore

[mgirlich]

stringr::str_detect("apple", rex::rex(maybe("a")))
#> Error in `type()`:
#> ! `pattern` must be a string

^{Created on 2022-02-23 by the reprex package (v2.0.1)}

This is because the change to the class names

regex() and friends now generate class names with stringr_ prefix

and stringr::type() is not exported so the rex package cannot create a correct type() method.

[hadley]

Maybe the easiest fix would be to just keep type.regex <- function(x) "regex" ?