Missing "overloaded contract" warnings when "more modules" are analyzed

[aronisstav]

Steps to reproduce (e.g. on 6e5cd3f):

$ dialyzer --build_plt --apps erts
[...]
$ dialyzer lib/stdlib/ebin/string.beam
[...]
string.erl:510: Overloaded contract for string:to_lower/1 has overlapping domains; such contracts are currently unsupported and are simply ignored
string.erl:522: Overloaded contract for string:to_upper/1 has overlapping domains; such contracts are currently unsupported and are simply ignored
Unknown functions:
  lists:append/1
Unknown types:
  io_lib:latin1_string/0
 done in 0m0.24s
done (warnings were emitted)
$ dialyzer lib/stdlib/ebin/*.beam
[...]
done (passed successfully)

[kostis]

OK, this one is not weird. The contract there is:

-spec to_lower(String) -> Result when
                  String :: io_lib:latin1_string(),
                  Result :: io_lib:latin1_string()
            ; (Char) -> CharResult when
                  Char :: char(),
                  CharResult :: char().

and because io_lib is not included in the analysis and io_lib:latin1_string() is an unknown type and assumed to be any() as far as the analysis is concerned, the analysis thinks that this is an overloaded contract. So there is no weirdness.

But of course dialyzer should not claim that the contract is overloaded when it involves an unknown type. The proper thing to do here is to completely disregard specs that involve unknown types (or treat them as being (any(), ..., any()) -> any()) and perhaps issue some message about it (i.e., that the spec was ignored due to unknown types).