Warn pipefail does not break in case of a background process

[Li0liQ]

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

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

#!/usr/bin/env bash
set -o pipefail
set -o errexit
false | tee &

Here's what shellcheck currently says:

Nothing.

Here's what I wanted or expected to see:

pipefail will not produce an error in case of a background process. Consider returning an exit code explicitly

#!/usr/bin/env bash
set -o pipefail
set -o errexit
{ 
 false | tee
 exit "${PIPESTATUS[0]}"
} &