SC2033: timeout (POSIX.1-2024) is not checked

[e-kwsm]

For bugs

• Rule Id (if any, e.g. SC1000): SC2032, SC2033
• My shellcheck version (shellcheck --version or 'online'): online
• I tried on shellcheck.net and verified that this is still a problem on the latest commit
• It's not reproducible on shellcheck.net, but I think that's because it's an OS, configuration or encoding issue

For new checks and feature suggestions

• 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/sh
foo() { ps -p $$; }
timeout 10 foo
# screen foo  # SC2033

Here's what shellcheck currently says:

Nothing.

Here's what I wanted or expected to see:

Line 2:
foo() { ps -p $$; }
^-- SC2032 (info): This function can't be invoked via screen on line 3.
 
Line 3:
timeout 10 foo
           ^-- SC2033 (warning): Shell functions can't be passed to external commands. Use separate script or sh -c.

timeout is now a POSIX utility, but is not checked like screen.