Just to expand on Araq's answer. It doesn't look like this defect is raised by
a `for loop`, because in Nim, in case where right boundary is less than left
e.g. `0 .. -1` loop block would never run:
let zero = 0
let c = zero
for i in 0 .. c - 1:
echo "You would never see this."
Run
Perhaps somewhere in your code you access `array` or `seq` of 13 elements with
an index that could be less than 0?
var Arr: array[13, int]
var Seq: seq[int] = @[0,1,2,3,4,5,6,7,8,9,10,11,12]
let zero = 0
let i = zero
echo Arr[i-1] # either of these two will give you
echo Seq[i-1] # Error: unhandled exception: index -1 not in 0 .. 12
[IndexDefect]
Run
