[erlang-questions] Wrong advertised spec of lists:append/2

[ok@REDACTED]

> The spec says both arguments and the result are lists.
> Indeed there is a contradiction with said spec. Isn't that a problem?

No, there isn't any contradiction with the specification.
It says "*IF* the arguments to append are lists,
the result will be a list".

It doesn't say "I promise to change reality so that no matter
what you do the arguments will be lists".