$ brew tap lambdalisue/neovim-qt

$ brew info neovim-qt
lambdalisue/neovim/neovim-qt: stable 0.2.8, HEAD
Neovim clinet library and GUI, in Qt5
https://github.com/equalsraf/neovim-qt
/usr/local/Cellar/neovim-qt/0.2.8 (13 files, 650KB) *
  Built from source on 2017-10-29 at 17:36:04
From: https://github.com/lambdalisue/homebrew-neovim/blob/master/neovim-qt.rb
==> Dependencies
Build: cmake ✔
Required: qt ✔, neovim ✔
==> Options
--without-release
        Build neovim-qt without -DCMAKE_BUILD_TYPE=Release
--HEAD
        Install HEAD version

$ brew install neovim-qt