Generating type specs programmatically

Hello list,

I've been working on a code-generating tool, leveraging `erl_syntax`[1] to
build an AST containing arbitrary Erlang functions; I then use `erl_pp`[2]
to generate the corresponding Erlang code and write the result onto a
source code file.

All is well so far, but now I want to generate type specs and function
specs with which to annotate the generated code - and I can't for the life
of me figure out how to do it within `erl_syntax`.

All of the different attempts I've made end up either crashing within
`erl_syntax` or `erl_pp`, or at best result in INVALID-FORM literals within
the generated code.

Would any of you be able to point me in the right direction?

Thanks in advance!

[1]: http://erlang.org/doc/man/erl_syntax.html
[2]: https://erlang.org/doc/man/erl_pp.html

-- 
Guilherme