[Animats]

The trouble with bounds checking via generics/macros is that the compiler doesn't know how to optimize out the checks. Most bounds checks can be optimized out of inner loops, where it really matters. But if the overflow test is just ordinary code, the compiler can't do that.

You also want to hoist bounds checks and do them early. Often, one check at loop entry can eliminate the bounds checks for each iteration. But the language has to allow an early fail.