AlwaysReturnSniff does not detect filters with no `return` statement

[nickdaugherty]

Bug Description

AlwaysReturnSniff doesn't actually trigger if the filter function doesn't include the return statement anywhere.

We have a bunch of tests to ensure AlwaysReturnSniff flags various problematic ways of returning from inside WP filters, but there is no test that ensures it raises a flag when return is omitted entirely.

Minimal Code Snippet

add_filter( 'bad_example_closure_with_no_returns', function( $input ) {
	$input = $input . ' hello!';

	// But we never return _anywhere_
}, 10, 2 );

Error Code

WordPressVIPMinimum.Filters.AlwaysReturn.missingReturnStatement

Environment

Use php -v and composer show to get versions.

Question	Answer
PHP version	7.1.19
PHP_CodeSniffer version	3.3.2
VIPCS version	master

Tested Against master branch?

• I have verified the issue still exists in the master branch of VIPCS.