SC2154 does not recognize variables declared in trap script

[olivergondza]

For bugs with existing features

• Rule Id: SC2154
• My shellcheck version (shellcheck --version or "online"): 0.11.0
• 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

Shellcheck reports variable used in trap statement is unassigned even if assigned earlier in the trap "script".

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

Mind the trap script is using single quotes - hence the variables are substituted during trap execution, not its declaration.

#!/usr/bin/env bash

trap 'exit_code=$?; echo >&2 "$0: Error on line "$LINENO": $BASH_COMMAND"; exit $exit_code' ERR

#!/usr/bin/env bash

trap 'let exit_code=$?; echo >&2 "$0: Error on line "$LINENO": $BASH_COMMAND"; exit $exit_code' ERR

#!/usr/bin/env bash

trap 'export exit_code=$?; echo >&2 "$0: Error on line "$LINENO": $BASH_COMMAND"; exit $exit_code' ERR

Here's what shellcheck currently says:

trap 'export exit_code=$?; echo >&2 "$0: Error on line "$LINENO": $BASH_COMMAND"; exit $exit_code' ERR
     ^-- SC2154 (warning): exit_code is referenced but not assigned.

Here's what I wanted or expected to see:

No errors 😎