There are even older languages with similar goals. At least three are called viper and are older than 6 years. Two linked below and much older one with ocaml-

There are even older languages with similar goals. At least three are called viper and are older than 6 years. Two linked below and much older one with ocaml-ish features that I could not find a link for. https://github.com/pdarragh/Viper https://github.com/pdarragh/Viper https://github.com/appcypher/viper https://github.com/appcypher/viper