Special parameter $# should be quoted in case numbers in IFS

[krushia]

For bugs with existing features

• Rule Id SC2086 (maybe?)
• My shellcheck version (shellcheck --version or "online"): online
• The rule's wiki page does not already cover this (e.g. https://shellcheck.net/wiki/SC2086)
• I tried on https://www.shellcheck.net/ and verified that this is still a problem on the latest commit

Here's a snippet or screenshot that shows the problem:

#!/bin/sh
f() {
while test $# -gt 0
do
 shift
done
}

IFS=0
f a b c

This will cause test to error when $# is 0, as it becomes test '' -gt 0

Here's what shellcheck currently says:

Nothing

Here's what I wanted or expected to see:

while test $# -gt 0
           ^-- SC2086 (info): Double quote to prevent globbing and word splitting.

[krushia]

Same problem exists with ${#foo} and $((foo)). It appears anything that looks like an integer has been erroneously whitelisted.

[serious-angel]

This is a mandatory and quite critical case to consider a warning for, indeed.
Thank you for the head-sup, @krushia ! 🛡️