False positive for SC2034; triggers when variable only used in "unset" command

[slycordinator]

For bugs with existing features

• Rule Id (if any, e.g. ): SC2034
• 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/bash

array=( foo bar baz )
del_index=1
unset 'array[del_index]'
for index in "${!array[@]}"; do
    echo "$index: ${array[$index]}"
done

Here's what shellcheck currently says:

Line 4:
del_index=1
^-- SC2034 (warning): del_index appears unused. Verify use (or export if used externally).

Here's what I wanted or expected to see:

(no output)

Note:
The erroneous warning is shown when I use either of:
unset 'array[del_index]'
unset 'array[$del_index]'

[nexushoratio]

As a work around, the following appears to both make shellcheck happy and function correctly:

unset "array[${del_index}]"                                                     |

That is, use double quotes and braces.