> The Haskell (Mu) compiler I wrote used no mutation, and the compilation speed up to, and including, type checking was about 15,000 lines/s. That was 5 years ago, so I expect it to be faster now.
>> I'm sorry to report that the current speed of Mu type-checking is somewhere around 1200 LoC/s. We aren't entirely sure what is the cause of the order-of-magnitude drop in speed, but we think maybe the large increase in type-level programming over the last 5 years could be a factor.