I'm not sure how this corresponds to your experience with Haskell, but as an OCaml user there's been numerous times where I have been forced to write large chunks of code without a compiler/IDE to aid me at all (e.g. VM wasn't working so had to work from Windows temporarily). In each of these cases, upon compilation, I have been greeted by a flood of errors (syntax errors, type errors, and everything in between). However, without exception, the program has always worked as expected when I ran it the first time. I think it's reasonably plausible that one could write a program the magnitude of ~5k lines in Haskell and have it work on the first attempt.