Why is F#'s type inference so fickle?

Question

The F# compiler appears to perform type inference in a (fairly) strict top-to-bottom, left-to-right fashion. This means you must do things like put all definitions before th

Answer 1

I think that the algorithm used by F# has the benefit that it is easy to (at least roughly) explain how it works, so once you understand it, you can have some expectations about the result.

The algorithm will always have some limitations. Currently, it is quite easy to understand them. For more complicated algorithms, this could be difficult. For example, I think you could run into situations where you think that the algorithm should be able to deduce something - but if it was general enough to cover the case, it would be non-decidable (e.g. could keep looping forever).

Another thought on this is that checking the code from the top to the bottom corresponds to how we read code (at least sometimes). So, maybe the fact that we tend to write the code in a way that enables type-inference also makes the code more readable for people...