Comment 2 for bug 1738071

This came up in mutation testing. I'm mutating valid forms by randomly inserting fragments of other valid forms, looking for situations that would cause SB-INT:BUG to be thrown by the compiler, or the compiler to outright crash (the previous bug with ASH/etc. running out of memory came up this way too). For this to work, errors should be catchable. I can get around it here by using timeouts, so this is not critical, but in general I'd prefer all problem to show themselves quickly.

Here, it would just require that ELT specially handle the case of large fixnums. In the common case of short lists this would mean just one extra check would be needed.