Squiz/NonExecutableCode: bug fix - expressions after PHP 7.0/7.4 null coalesce (equals)

PHP 7.0 introduced the null coalesce operator.
PHP 7.4 introduced the null coalesce equals operator.

The `T_EXIT` token can be used in combination with those without affecting the code directly following it.

See: https://3v4l.org/C218d#veol

Fixed now.

Includes unit test.

Related to 2857

Author: jrfnl

src/Standards/Squiz/Sniffs/PHP/NonExecutableCodeSniff.php

@@ -73,6 +73,11 @@ public function process(File $phpcsFile, $stackPtr)
             if ($tokens[$prev]['code'] === T_INLINE_THEN || $tokens[$prev]['code'] === T_INLINE_ELSE) {
                 return;
             }
+
+            // Expressions are allowed with PHP 7.0+ null coalesce and PHP 7.4+ null coalesce equals.
+            if ($tokens[$prev]['code'] === T_COALESCE || $tokens[$prev]['code'] === T_COALESCE_EQUAL) {
+                return;
+            }
         }
 
         // Check if this token is actually part of a one-line IF or ELSE statement.

src/Standards/Squiz/Tests/PHP/NonExecutableCodeUnitTest.1.inc

@@ -335,5 +335,12 @@ function exitExpressionsInTernary() {
     echo 'still executable';
 }
 
+// Inline expressions are allowed with null coalesce and null coalesce equals.
+function exitExpressionsWithNullCoalesce() {
+    $value = $nullableValue ?? exit();
+    $value ??= die();
+    echo 'still executable';
+}
+
 // Intentional syntax error.
 return array_map(