currently in edge cases when there's an ambiguous match e.g.

java.io.File.new('.').listFiles { ... } (2 method exists that accept a single function-interface argument)

no matter the passed Proc's arity the FileFilter#accept(File) seems to be used (with a warning being printed) while with { |arg1, arg2| } we can assume that FilenameFilter#accept(File, String) is more desired than the FileFilter#accept(File)

UPDATE: which method will be used will currently depend on env (returned method order)!