How much of it was haskell, and how much of it was just working with a statically typed language?
Haskell is also astoundingly terse. In Java and C my data type declarations were too long to fit on a page, full of redundancies and boilerplate. In Haskell if you want to make, say, a data type that is either an X or an O (suppose you're writing tic-tac-toe), you could do it in four words: 'data XO = X | O'. (Notice that there's not even a natural way to do that in Java or C, because they don't have sum types; you'd have to make a type that has a flag to indicate whether it is an X or an O. That gets really complicated if they're supposed to have different data associated with it -- but in Haskell, if the X is supposed to carry a float and the O is supposed to carry a string, you just add two more words.)
Pattern matching also helps with terseness. I don't have time even to write the last paragraph so I'll skip this one.
Purity keeps you from tripping up on IO-related errors. It lets you be much more certain that things are working. It also forces you to keep the IO in a thin top-level layer of your program, which might sound like a pain but once it feels natural you'll find yourself moving faster than you could before.
To be sure, Haskell has features that I don't use. But purity, sum types, pattern matching, and the unusually rigorous (it's complete!) type system are all critical to its value to me.
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!
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.
My codebase is only a few thousand lines, though.
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.