SC2119 / SC2120 false positives?

[dubo-dubon-duponey]

For bugs

• Rule Id (if any, e.g. SC1000): SC2119 / SC2120
• My shellcheck version (shellcheck --version or "online"): online and 0.9.0
• 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

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

#!/usr/bin/env bash

foo(){
        local input="${1:-/dev/stdin}"
        cat "$input"
}


foo <<<"blah"

Here's what shellcheck currently says:

In test.sh line 3:
foo(){
^-- SC2120 (warning): foo references arguments, but none are ever passed.


In test.sh line 9:
foo <<<"blah"
^-----------^ SC2119 (info): Use foo "$@" if function's $1 should mean script's $1.

For more information:
  https://www.shellcheck.net/wiki/SC2120 -- foo references arguments, but non...
  https://www.shellcheck.net/wiki/SC2119 -- Use foo "$@" if function's $1 sho...

Here's what I wanted or expected to see:

It should say nothing about SC2120. An argument is being passed (a file descriptor), so, this one feels factually wrong to me.

SC2119, I am not quite sure what it would mean here, so, same thing, I would expect it to not say anything.

Apologies in advance if I am missing something here.

Thanks a lot!