Request for support nonempty_improper_list() type

[jj1bdx]

When I tried to test a piece of code here
https://github.com/jj1bdx/exsplus116/blob/ba2429466925b1baeb5a81d183b67e092c548994/src/exsplus116.erl#L55
An error message showed up rendering the type into any().
The usage of nonempty_improper_list() was for a optimization which actually also exists in the rand module:
https://github.com/erlang/otp/blob/OTP-18.2.4/lib/stdlib/src/rand.erl#L257

(I know this is a rare case but I will raise an issue FYI for your further decision.)

kenji@silverblade[1043]% ~/src/cuter/cuter exsplus116 next '[[287716055029699555|144656421928717457]]' -d 50 -s 4 -p 4   Testing exsplus116:next/1 ...

WARNING: The spec of {exsplus116,next,1} uses the unsupported type nonempty_improper_list!
  It has been generalized to any().

.
exsplus116:next(0)

exsplus116:next([0])

=== Inputs That Lead to Runtime Errors ===
#1 exsplus116:next(0)
#2 exsplus116:next([0])

=== BIFs Currently without Symbolic Interpretation ===
erlang:'bsl'/2
erlang:'bxor'/2
erlang:'bsr'/2
erlang:'band'/2