[tcopeland]

Here's a longer article (http://codon.com/consider-static-typing) with more background / history about static typing and Ruby.

This topic has been knocked around in Ruby-land for a while; I remember seeing Michael Edgar's LASER (https://github.com/michaeledgar/laser) static analysis tool including some work around optional type annotations, but seems like development there has stopped.

[infraruby]

InfraRuby is a statically-typed Ruby (compiles to the JVM). InfraRuby code runs on Ruby interpreters without modification: http://infraruby.com/blog/why-infraruby

[zeckalpha]

Re: Ruby: There's http://crystal-lang.org/, too.