SC2031 missing issues with process substitution (<())

[stdedos]

For bugs

• Rule Id (if any, e.g. SC1000): SC2031
• My shellcheck version (shellcheck --version or "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

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:

#!/bin/bash

set -Eeuo pipefail

random_fail() {
  if [ $((RANDOM % 100)) -lt 50 ]; then
    return 1
  fi
  return 0
}

random_fail | tee /tmp/a

# I don't want this to fail immediately, but I want the exit code
# ... also I have other pipes I want to guard against (instead of "consuming" the $?)

(random_fail && RC=0 || RC=$?) | tee /tmp/a
echo "RC: $RC"

# But that triggers SC2030/SC2031. There's a suggestion about using <(), so ... might work?

tee /tmp/a < <(random_fail && RC=0 || RC=$?)
echo "RC: $RC"

# Fun fact: It won't

Here's what shellcheck currently says:

[Line 17:](javascript:setPosition(17, 17))
(random_fail && RC=0 || RC=$?) | tee /tmp/a
                ^-- [SC2030](https://www.shellcheck.net/wiki/SC2030) (info): Modification of RC is local (to subshell caused by (..) group).
 
[Line 18:](javascript:setPosition(18, 11))
echo "RC: $RC"
          ^-- [SC2031](https://www.shellcheck.net/wiki/SC2031) (info): RC was modified in a subshell. That change might be lost.

Here's what I wanted or expected to see:

+ Also for l22, l23

[stdedos]

Solution for the ones who are searching:

if random_fail | tee /tmp/a ; then
  RC=0
else
  RC=$?
fi