Create a prop that's like `for`

[lvh]

I grabbed the title out of a TODO referencing this code in regexes-test:

(prop/for-all [[re s] (gen'/for [re-s (gen/elements generator-regression-cases)
                                   :let [re (re-pattern re-s)]
                                   s (regexes/gen-string-from-regex re)]
                          [re s])]
    (re-matches re s))

Figured it should be a ticket instead :)

[gfredericks]

yeah that sounds fine :)