Bug 4907 – Catching more simple out-of-bounds errors at compile-time

One of the advantages of static typing is that it catches some classes of bugs early, instead of later at runtime. Similarly, catching array out-of-bounds errors early at compile-time is better than catching them at run-time in debug builds. Catching all cases of out-of-bounds errors at compile time is not possible and it's hard to do, but there are simple cases that are common coding mistakes and probably easy to catch at compile-time: void main() { int[10] arr; for (int i = 0; i <= arr.length; i++) arr[i] = i; } In idiomatic D that kind of bugs is less common because explicitly bounded loops are less common: void main() { int[10] arr; foreach (i, ref x; arr) x = i; } But probably there are enough D programmers that don't use idiomatic D or translate code from Java/C/C++/C# code that contains explicit loops. Currently DMD is able to spot such out-of-bounds errors at compile-time only if the index is a compile-time constant: const int i = 6 / 2; void main() { int[3] arr; arr[i] = 3; // Error: array index 3 is out of bounds arr[0 .. 3] }

Well, this check amounts to adding a special case in the compiler for no apparent benefit since you end up with an assertion error at runtime anyway. I don't think this is worth it.