@fossMan Firstly, Wayland itself is not a library, so there will be no "autocomplete" for it. It's a protocol definition, which Mir implements. So you'd need just the Mir APIs to be completed.
I don't know much about what all the fancy IDEs need for that, but it should be pretty easy to generate ctags definitions for Mir, which should work with several editors (like emacs or vim). I would expect some IDEs should be able to handle them as well, but I don't know.