Seems like this has been an issue for a while:

https://github.com/pragdave/earmark/issues/141

One thing that stands out: both doctests and code-blocks use a four space indent, starting from the surrounding content. Your example only indents two spaces:

https://github.com/RooSoft/bitcoinlib/blob/9c96f0a96c8fc0d2bedca7b654c290f143bb06fd/lib/key/hd/mnemonic_seed/wordlist.ex#L37-L39

I’ve indented it further to 4, and the warning disappeared!

Thanks al2o3cr!

Will reindent, but that’s definitely not ideal…

One could discuss if IAL makes sense for ex_doc maybe you should discuss it with them, however the correct way to escape IAL is as follows

iex(9)> EarmarkParser.as_ast("a\n\\{:a, 1}")
{:ok, [{"p", [], ["a\n{:a, 1}"], %{}}], []}

I found that this error can also occur for some tuples in @doc code:

    Perform a license check.

    ## Arguments

    * The first argument is the result of the license check.
    * The second argument is {params, socket.assigns}

    ## Return

    * true for success
    * {:error, error_atom} for failure.

Only the line containing {:error, error_atom} generated a warning, and interestingly complaining about the two parts in reverse order (as they were for RooSoft). Adding back ticks around the tuple resolved the issue for me.