false positives SC2154, SC2034 and SC2209 for associative array

[coiby]

For bugs

• Rule Id (if any, e.g. SC1000): SC2154, SC2034 and SC2209
• My shellcheck version (shellcheck --version or "online"):

shellcheck --version          
ShellCheck - shell script analysis tool
version: 0.8.0
license: GNU General Public License, version 3
website: https://www.shellcheck.net

• 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

For new checks and feature suggestions

• https://www.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
  • False positive for SC2154 when dereferencing an associative array inside arithmetic evaluation command #1074 is related but already fixed

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

#!/bin/bash
test_arr()
{
    local -n farr=$1

    farr[c]=cc
    farr[d]=dd
    farr[keb]=dd
    echo "${farr[*]}"
}

declare -A arr

arr[a]=aa
arr[b]=bb
test_arr arr

Here's what shellcheck currently says:

In associate_array.sh line 6:
    farr[c]=cc
         ^-- SC2154 (warning): c is referenced but not assigned.


In associate_array.sh line 7:
    farr[d]=dd
    ^-----^ SC2209 (warning): Use var=$(command) to assign output (or quote to assign string).
         ^-- SC2154 (warning): d is referenced but not assigned.


In associate_array.sh line 8:
    farr[keb]=dd
    ^-------^ SC2209 (warning): Use var=$(command) to assign output (or quote to assign string).
         ^-^ SC2154 (warning): keb is referenced but not assigned.


In associate_array.sh line 16:
arr[ab]=aabb
^-----^ SC2034 (warning): arr appears unused. Verify use (or export if used externally).

For more information:
  https://www.shellcheck.net/wiki/SC2034 -- arr appears unused. Verify use (o...
  https://www.shellcheck.net/wiki/SC2154 -- c is referenced but not assigned.
  https://www.shellcheck.net/wiki/SC2209 -- Use var=$(command) to assign outp...

Here's what I wanted or expected to see:

empty result

[petersenna]

Here is what I have:

    VM_EXTRA_OPTS=('--boot-disk-size=40G')

    VM_SELFLINK=$(gcp_vm create --image "$VMTEMPLATE_GCP_IMAGE_URL" \
                --delete-after "$VM_DELETE_TIMEOUT_MINUTES" \
                --extra-opts VM_EXTRA_OPTS)

And I got an SC2034 warning about VM_EXTRA_OPTS.

[matthewpersico]

More examples:

declare -A hash

hash[foo]=1
hash[bar]=2
hash[biz]=3
echo '#' "$(set | grep -E '^hash=')"
# hash=([biz]="3" [bar]="2" [foo]="1" )

unset 'hash[foo]'
echo '#' "$(set | grep -E '^hash=')"
# hash=([biz]="3" [bar]="2" )

declare key='bar'
unset 'hash[$key]'
echo '#' "$(set | grep -E '^hash=')"
# hash=([biz]="3" )

So this code all worked. But shellecheck.net complained:

Line 7:
hash[biz]=3
^-- [SC2034](https://github.com/koalaman/shellcheck/wiki/SC2034) (warning): hash appears unused. Verify use (or export if used externally).
__I think that's wrong; we use it in the unset.__
 
Line 15:
declare key='bar'
        ^-- [SC2034](https://github.com/koalaman/shellcheck/wiki/SC2034) (warning): key appears unused. Verify use (or export if used externally).
__That's definitely wrong; we use it in the unset.__