Why is the Rust compiler so slow?

I’m glad that Go went the other way around: compilation speed over optimization.

For the kind of work I do — writing servers, networking, and glue code — fast compilation is absolutely paramount. At the same time, I want some type safety, but not the overly obnoxious kind that won’t let me sloppily prototype. Also, the GC helps. So I’ll gladly pay the price. Not having to deal with sigil soup is another plus point.

I guess Google’s years of experience led to the conclusion that, for software development to scale, a simple type system, GC, and wicked fast compilation speed are more important than raw runtime throughput and semantic correctness. Given the amount of networking and large - scale infrastructure software written in Go, I think they absolutely nailed it.

But of course there are places where GC can’t be tolerated or correctness matters more than development speed. But I don’t work in that arena and am quite happy with the tradeoffs that Go made.

What are obnoxious types? Types either represent the data correctly or not. I think you can force types to shut up the compiler in any language including Haskell, Idris, PureScript...

I'd say you already get like 70% of the benefit of a type system with just the basic "you can't pass an int where string is expected". Being able to define your own types based on the basic ones, like "type Email string", so it's no longer possible to pass a "string" where "Email" is expected gets you to 80%. Add Result and Optional types (or arguably just sum types if you prefer) and you're at 95%. Anything more and you're pushing into diminishing returns.

Well it depends what you're doing. 95% is like, just your opinion man. The rust type system allows, in many cases, APIs that you cannot use wrongly, or are highly resistant to incorrect usage, but to do that requires careful thinking about. To be clear, such APIs are just as relevant internally to a project as externally if you want to design a system that is long term maintainable and robust and I would argue is the point when the type system starts to get really useful (rather than diminishing returns).