.add missing from IO::Path?

[Gabor Szabo]

Reading https://docs.perl6.org/type/IO::Path#method_child
I thought I need to use .child or .add but .add does not seem to work:

"foo/bar".IO.add("def")
No such method 'add' for invocant of type 'IO::Path'
  in block <unit> at <unknown file> line 1


Gabor