SC2320 warning in function

[BrentHuang]

For bugs

• Rule Id (if any, e.g. SC1000): SC2320
• My shellcheck version (shellcheck --version or "online"): 0.10.0
• 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

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

demo() {
    echo "in function demo..."
    echo "the script name: $0"
    echo "argument count (not include the script itself): $#"
    echo "the first argument: $1"
    echo "the second argument: $2"
    echo "the 10th argument: ${10}"

    # shellcheck disable=SC2145
    echo "argument list: $@"  # echo 输出字符串，这里 shellcheck 会告警，字符串形式用 $* 就不会告警
    echo "argument list string: $*"
    echo "process id: $$"

    ret=$?
    echo "command exited with ${ret}"
    if [[ ${ret} -ne 0 ]]; then
        echo "failed"
    fi
}

demo 1 2 3

Here's what shellcheck currently says:

In ./docs/test.sh line 16:
ret=$?
^-- SC2320 (warning): This $? refers to echo/printf, not a previous command. Assign to variable to avoid it being overwritten.

Here's what I wanted or expected to see:

no SC2320 warning.