Report error for `set -v` used in blocks/conditions

[kkmuffme]

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

if [[ "foo" == "$1" ]]
then
        set -v
        echo "hello"
fi

Here's what shellcheck currently says:

No issues detected!

Here's what I wanted or expected to see:

An error that set -v and set +v inside blocks do not have any effect, since this is unexpected, as all (?) other "set" work independently of where they're placed