Use EDoc link for erlang type

[chulkilee]

Fixes #1005

[wojtekmach]

Looks good to me.

FWIW, people can do:

defmodule :foo do
  @moduledoc "..."
end

and ExDoc will generate docs for it, so the heuristic that :module is documented using EDoc fails here. Personally I think it's an ok heuristic, but just mentioning this for completeness.

Fixes #1005

This PR only solves part of the problem, in order to close #1005 we'd need to make this work as well.

@moduledoc """
See `t::sets.set/0`.
"""

If you'd like to work on that aspect in a separate PR, that would be appreciated!

[chulkilee]

@wojtekmach Oh, I didn't know that's possible (defmodule :foo). However, how can we know whether the referenced name is erlang or elixir? That seems impossible without this heuristic..

I'm not sure looking into alias is a good idea actually. Probably the language should be passed down to type_remote_url function - but I'm not sure that's even possible.

[josevalim]

In this case wouldn’t it be better to look at the original text and see if it stars with “:”? -- *José Valimwww.plataformatec.com.br <http://www.plataformatec.com.br/>Founder and Director of R&D*

[wojtekmach]

However, how can we know whether the referenced name is erlang or elixir? That seems impossible without this heuristic..

As @josevalim wrote here

Would checking in deps for mix.exs or rebar.config be out of the question?

I actually like this idea. the Mix integration already looks for dependencies in there. We can possibly see if the manager is :mix and not include the dependencies otherwise.

so it's not a matter of whether it's Erlang or Elixir, but what tool was used to build the documentation for that particular module.

As José mentioned elsewhere, given different Erlang projects might use different tools, it's a safer bet to only use EDoc style urls for Erlang stdlib and leave others not linked.

[chulkilee]

As José mentioned elsewhere, given different Erlang projects might use different tools, it's a safer bet to only use EDoc style urls for Erlang stdlib and leave others not linked.

@josevalim mentioned that at #1066 (comment)

I'm going to close this PR as it's not clear "adding more link to external erlang project" is the "right" direction to go at this moment.