Auto merge of #3742 - matklad:sets-are-monoid, r=alexcrichton
authorbors <bors@rust-lang.org>
Sat, 25 Feb 2017 07:32:31 +0000 (07:32 +0000)
committerbors <bors@rust-lang.org>
Sat, 25 Feb 2017 07:32:31 +0000 (07:32 +0000)
commit163de44297b052c8c8668f75a51029b6ed8a0416
treed0637942affd68c5717fdb37e14a82d42a83c3f4
parentb2dc77f6350d9a58b8d4b7ea338e7a09fb97d9c1
parent50f1c172aeb3f340ae654c82e430bd47731ad8d3
Auto merge of #3742 - matklad:sets-are-monoid, r=alexcrichton

Simplify feature-handling code

A neat (imo :) ) hack to use an empty `&HashSet` instead of `Option<&HashSet>`.