Academic language designers do! But it takes a while for academic features to trickle down to practical languages—especially because expressive-enough refinement typing on even the integers leads to an undecidable theory.
I think the reasons are predominantly social, not theoretical.
For every engineer out there that gets excited when I say the words "refinement types" there are twenty that either give me a blank stare or scoff at the thought, since they a priori consider any idea that isn't already in their favorite (primitivistic) language either too complicated or too useless.
Then they go and reinvent it as a static analysis layer on top of the language and give it their own name and pat themselves on the back for "inventing" such a great check. They don't read computer science papers.
Hello! I was curious if you would happen to have any advice or particular comp sci papers you would point as aspiring compiler developer towards.
I think I'm sort of who you're talking about. I have no formal education and I am excited to have my compiler up to the point I can run a basic web server. I think it's a fairly traditional approach with a lexer, recursive decent parser, static analysis, then codegen. I'm going for a balance between languages like Ruby and Rust to get the best of both worlds.
You'll probably find it funny that I don't know the name for the technique Im using for dynamic dispatch. The idea is that as long as a collection doesn't have mixed types then the compiler statically knows the type even in loops and such. Only for mixed type collections, or maybe trait functions, will the compiler be forced to fall back to runtime dynamic dispatch. I find this cool because experts can write fast static code, but beginners won't be blocked by the compiler complaining about things they shouldn't have to care about yet. But, syntax highlighting or something may hint there are improvements to be made. If there is a name for this, or if it's too small a piece to deserve one, I would be very curious to know!
On Refinement Types, I not sure they are a good idea for general purpose languages and would love to be challenged on this. Succinctly, I think it's a leaky abstraction. To elaborate, having something like a `OneThroughTen` type seems helpful at first, but in reality it's spreading behaviour potentially all over the app as opposed to having a single function with the desired behaviour. If a developer has multiple spots they're generating a number and one spot is missing a check and causes a bug, then hopefully a lesson was learned not to do that and instead have a single spot for that logic. The heavy handed complexity of Refinement Types is not worth it to solve this situation.
If there are any thoughts out there they would be greatly appreciated!
Aren't most type systems in widely used languages Turing complete and (consequently) undecidable? Typescript and python are two examples that come to mind
But yeah maybe expressive enough refinement typing leads to hard to write and slow type inference engines
