{'EXIT', {badarg, [{erlang,atom_to_list, ...}]}} in proper_gen_next.erl

[albsch]

Generating atom()s with the ?FORALL and ?EXISTS seems to crash proper.

init terminating in do_boot ({badarg,[{erlang,atom_to_list,[{_}],[{_}]},{proper_gen_next,-atom_gen_sa/1-fun-0-,3,[{_},{_}]},{proper_gen_next,restrict_generation,6,[{_},{_}]},{proper_gen,generate,3,[{_},{_}]},{proper_gen,generate,1,[{_},{_}]},{proper_gen,safe_generate,1,[{_},{_}]},{proper_gen_next,-apply_parameters/2-fun-1-,4,[{_},{_}]},{proper_sa,next,2,[{_},{_}]}]})

Property in question:

?FORALL(L1, atom(), 
    ?EXISTS(L2, atom(), 
      L1 =:= L2
    )
  )

A minimal crash-reproducing example can be found here:

https://github.com/albsch/buggy_proper

Versions tested: OTP 21-24, PropEr 1.3.0 and 1.4.0.

Might be related to #190 ?