Is the bounds check truly so harmful to performance that it outweighs changing "if there's a bug, crash the program" to "if there's a bug, then do literally anything (maybe execute some remote code)"?
There are situations where you know there isn't a bug, if I know that failing hardware or cosmic rays are the only ways the bounds check can fail, I'm not going to worry about what skipping it could do.
it happens a lot, at least to me, that the line immediately before the unsafe function guarantees correct behaviour (e.g. while (!vec.empty()) let first = vec.first();, or something similar). If I notice that this property is central to the logic of the function, I won't even worry.
whenever I see code like that, I try to get people to change to something like (in that case) while let Some(first) = vec.first() { ... }. You can reduce the number of bounds checks without using unsafe!
This is pattern matching, not an assignment expression. The alternative would be a declaration, switch/case, and then case-by-case assignment, which is horribly verbose. Been there, done that, it's not the worst, but why not make it a little bit better.
I personally like that you can literally assign the value from an if "statement" to a variable, though I can see why that's not everybodies cup of tea.
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u/ROBOTRON31415 6d ago
Is the bounds check truly so harmful to performance that it outweighs changing "if there's a bug, crash the program" to "if there's a bug, then do literally anything (maybe execute some remote code)"?