PHP version compatibility

When upgrading from 4.0.17 to 4.0.21 on a Drupal 9 with PHP 7.4, the following error occurs :

ParseError: syntax error, unexpected ')', expecting variable (T_VARIABLE) in Composer\Autoload\{closure}() (line 96 of modules/contrib/environment_indicator/src/ToolbarHandler.php).

If PHP < 8.0 is not supported anymore :

• it should be reflected in the composer.json
• it shoud at least be a minor version and not a bug fix version