I agree that to compete with Ruby ergonomics one probably needs a GC. I think part of what I'm getting at is that there are other ways to approach these problems, and aping Ruby isn't necessarily one I prefer. Not to knock Crystal, it seems very cool.

Re: application domains, I've recently been doing some work in CPU/memory constrained applications (not embedded, running big >500GB jobs on HPC clusters), and a GC is unfortunately a non-starter for this kind of data processing.

I have also been watching with great anticipation the work being done on "big data" processing with Rust (https://github.com/frankmcsherry/timely-dataflow) and how that might obviate the need for a GC with the various JVM RAM-hogs which dominate that field.

There are also many areas where people work (many of whom provide the tools that programmers of GC'd languages use for their jobs) which can't admit a garbage collector.

For example, I currently deploy Django code (running on an interpreter that needs to implement, not run on top of, a GC) to a machine with a Linux kernel, running nginx, backed by another machine running PostgreSQL, with caching in Redis. None of those very important tools can reasonably offer the performance needed in a garbage collected language.

For another example, I'm typing this (quite lengthy) response in a low-latency application (a browser) which would also be difficult to implement in a garbage-collected language.