The idea there:
"Graal is a research compiler. ... Truffle is a framework for implementing languages using nothing more than a simple abstract syntax tree interpreter."
As a bonus, you get high speed, good instrumentation for debugging and profiling, with great garbage collection, and hotswap code as you develop.
https://blog.plan99.net/graal-truffle-134d8f28fb69
discussed at https://news.ycombinator.com/item?id=13343845
The idea there: "Graal is a research compiler. ... Truffle is a framework for implementing languages using nothing more than a simple abstract syntax tree interpreter."
As a bonus, you get high speed, good instrumentation for debugging and profiling, with great garbage collection, and hotswap code as you develop.