elixir-lang/elixir — pull request #391 by yrashk (2012-07-13 00:30:42+00:00)
Title: Fixes a bug that broke the correct behavior of the `in` guard

The correct behavior is:

> [] in [1,2,3] == false

However, recently introduced bug made this work like this:

> [] in [1,2,3] == true