Error: qt@5.5: unknown version :mountain_lion

Question

Followed this tutorial in installing qt5.5 on a macOS version 10.13.6 High Sierra. Failed when trying to brew install qt@5.5 giving me an error below:

Answer 1

Referring to the tutorial, the following steps are executed to install qt@5.5

brew update
cd $( brew --prefix )/Homebrew/Library/Taps/homebrew/homebrew-core

# below is the last commit containing qt@5.5 with homebrew
git checkout 9ba3d6ef8891e5c15dbdc9333f857b13711d4e97 Formula/qt@5.5.rb

# here is where the error occurs
brew install qt@5.5

Solution

turns out line 25 of qt@5.5.rb formula file checked out in the command ( as seen in the referred tutorial)

git checkout 9ba3d6ef8891e5c15dbdc9333f857b13711d4e97 Formula/qt@5.5.rb

is causing this problem. commenting it out fixes the issue