Hmm it might then be a good idea to apply the robustness principle if not too costly.
Maybe the transformer should accept also extended tuples in the AST, e.g.
{:code, [], children, _}
That would allow AST transformers to leave their annotations.
However it will fence us in concerning later extensions of the AST format, an alternative would be to allow only
{:code, [], children, {:meta, _}}
