Catch undefined commands / functions

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

Is it possible to generate warning for undefined command / function? The use case is to catch typos. In practice, I'm okay to maintain a dictionary of command / function names.

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

#!/bin/bash

echa "hello world"

Here's what shellcheck currently says:

No issues detected!

Here's what I wanted or expected to see:

Unknown command "echa"