ksh set -A not recognized as an assignment

[sckendall2]

For bugs

• Rule Id (if any, e.g. SC1000): SC2154
• My shellcheck version (shellcheck --version or 'online'): online
• I tried on shellcheck.net and verified that this is still a problem on the latest commit
• It's not reproducible on shellcheck.net, but I think that's because it's an OS, configuration or encoding issue

For new checks and feature suggestions

• shellcheck.net (i.e. the latest commit) currently gives no useful warnings about this
• I searched through https://github.com/koalaman/shellcheck/issues and didn't find anything related

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

#! /bin/ksh
set -A a
print ${#a[@]}

Here's what shellcheck currently says:

Line 3	SC2154: a is referenced but not assigned.

Here's what I wanted or expected to see:

No warning. In KornShell, set -A a creates the empty indexed array a.