In Rust, it's considered a bug for any code which isn't using `unsafe` to encounter a memory error (e.g., to segfault). That bug might be in some underlying library (which is itself using `unsafe`), or more rarely in the compiler, but it's a bug and not how Rust is supposed to work.

Does Haskell have any similar line? What is the property that code must have in order for it to be a bug to segfault? Must not call `unsafePerformIO`? Must not call `unsafeCoerce`? (Must not call any function with the `unsafe` prefix?)

In other words, is the segfault here to be considered a bug in the language -- or is unwrapping IO one of the things that, if you do it, you're own your own and may segfault? (Is part of the point of the article is that it is currently considered safe but should not be? Is that a bug in the language or in peoples' expectations?)

Or is a clear line like this not a notion that Haskell has? It's been a long time since I've done any Haskell, though I don't recall any clear guideline like this!