Naturally for a language based off Ruby, the original compiler was written in Ruby. It became self-hosting in late 2013: https://crystal-lang.org/2013/11/14/goo

Naturally for a language based off Ruby, the original compiler was written in Ruby. It became self-hosting in late 2013: https://crystal-lang.org/2013/11/14/good-bye-ruby-thursday.html https://crystal-lang.org/2013/11/14/good-bye-ruby-thursday.h...