meta-object

For a meta-object protocol, you'll need however still a little bit help to avoid creating too many guards.

Thus you get an object system with meta-object protcol, and you can extend the syntax through user-defined grammars.

Pulling in the meta-object library ('use Moose') was guaranteed to make your program take a long time to start.

Tech lead Jochen Theodorou in 2005-2006 helped build the meta-object protocol that Grails also uses.

Beanshell's also an older language, which Groovy cloned and added closures (since made obsolete by Java 8's lambdas) and a meta-object protocol to.

If you're interested in a beautifully-designed approach to meta-programming (reflection and reification), 'The Art of the Meta-Object Protocol' (Kiczales et al.) is absolutely wonderful.

Graeme Rocher had a meta-object protocol added to Groovy so he could bundle it as the scripting language of Grails (used just like Ruby is in Rails).

On the other end of the spectrum are many compiled Lisp implementations which allow various changes to the programming language at runtime, for example via an extensive meta-object protocol.

> The redesign allowed us to completely remove the Qt Meta-Object Compiler (moc) system.

Take another JVM language Groovy -- it's used a lot for scripting throwaways used in testing, including build files for Gradle, and was extended with a meta-object protocol for Grails which has risen and fallen in sync with Rails.

Or is it that I'm being too optimistic about the tracer -- and with a generalized PIC one isn't relying upon the tracer to get it right, but forcing a cache on meta-object protocol boundaries?

NB: By "Groovy (the scripting version)" I mean the component of Groovy which was Beanshell with closures and collections syntax added, but before the meta-object protocol was.