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That complicated type system w/ type inference does come with it's own costs, usually bad compile speed issues. It's what I've noticed when looking at languages like swift, rust, scala & haskell.

I'm currently dealing with it in a large swift project, and I would much rather go back to the extra verbosity of objective-c than have type inference at this point.

But that was insightful, thank you!




The type system is probably not the bottleneck in any of those cases. As a sibling comment points out, ocaml has very good compile times, and the inference problem is basically the same as in Haskell.

In the case of rust, I suspect one of the biggest issues is the way parametric polymorphism is implemented. Basically, if in your program you end up using e.g. Box<usize>, Box<MyType> and Box<Result<String>>, you're compiling Box 3 times.

I don't know enough about swift to hazard a guess as to where the build is spending its time.

My experience with Haskell is that compile times are neither great nor terrible.


Check out OCaml (BuckleScript or ReasonML on the frontend, depending on which syntax you prefer). It has a super-fast compiler with almost total global type inference. The Facebook Messenger team report incremental builds of less than a second.


Data point : I’m working on a several hundred thousand line server using Scala. The incremental compile time is usually 2 or 3 seconds. A clean build of the project is around 2 minutes


Have you noticed slow compiling with Haskell specifically?


I've only used swift at that size, but I've heard stories with all of those languages once you have a large code base.

I remember vaguely reading about how at a haskell conference people were basically cornering compiler maintainers about compile speed, but that was several years ago.


When I have to recompile, it's usually because I've only modified a few files, and it's usually really fast. I particularly enjoy that if I refactor things without actually making any changes in the way it works, GHC won't blink; it knows there's nothing to do.

My codebase is only a few thousand lines, though.


Yeah the codebases I'm talking about are something around 1 million lines over several apps, libraries, all of the tests and codegened models, mocks and network services.




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