…thods (nicolas-grekas)This PR was merged into the 6.0 branch.Discussion----------Add return type unions to private/internal/final/test methods| Q             | A| ------------- | ---| Branch?       | 6.0| Bug fix?      | no| New feature?  | no| Deprecations? | no| Tickets       | -| License       | MIT| Doc PR        | -Spotted thanks to progress made on#42149Commits-------af7ff7e Add return type unions to private/internal/final/test methods

…est methods (nicolas-grekas)This PR was merged into the 6.0 branch.Discussion----------Narrow existing return types on private/internal/final/test methods| Q             | A| ------------- | ---| Branch?       | 6.0| Bug fix?      | no| New feature?  | no| Deprecations? | no| Tickets       | -| License       | MIT| Doc PR        | -More progress from#42149Commits-------d67a927 Narrow existing return types on private/internal/final/test methods

This PR was merged into the 5.4 branch.Discussion----------More return type fixes| Q             | A| ------------- | ---| Branch?       | 5.4| Bug fix?      | no| New feature?  | no| Deprecations? | no| Tickets       | -| License       | MIT| Doc PR        | -Extracted from#42149Commits-------f7abdec More return type fixes

… (nicolas-grekas)This PR was merged into the 5.4 branch.Discussion----------Add missing return types to tests/internal/final methods| Q             | A| ------------- | ---| Branch?       | 5.4| Bug fix?      | no| New feature?  | no| Deprecations? | no| Tickets       | -| License       | MIT| Doc PR        | -Thanks to#42149 againCommits-------0f39a0f Add missing return types to tests/internal/final methods

…cations by default + add mode to turn them into native types (nicolas-grekas)This PR was merged into the 5.4 branch.Discussion----------[ErrorHandler] Turn return-type annotations into deprecations by default + add mode to turn them into native types| Q             | A| ------------- | ---| Branch?       | 5.4| Bug fix?      | no| New feature?  | yes| Deprecations? | no| Tickets       | -| License       | MIT| Doc PR        | -Leverages#42149We need extensive doc on the topic for sure, a whole new chapter.DebugClassLoader allows patching an app or a lib by going through these steps:- require `symfony/error-handler` if not already there- run `composer install -q --optimize-autoloader`- copy/paste the below script to the root of the app/lib, in `patch-types.php`- run the script with `SYMFONY_PATCH_TYPE_DECLARATIONS='force=phpdoc' php patch-types.php``SYMFONY_PATCH_TYPE_DECLARATIONS` can be set to:- `'force=phpdoc'` to copy ``@return`` annotations from parent classes, to express that the next major version of that lib is going to add a native return types;- `'force=1'` to turn ``@return`` annotations into native return types, but only on tests/private/final/internal methods;- `'force=2'` to turn ``@return`` annotations into native return types, for all possible methods.```php<?phpif (false === getenv('SYMFONY_PATCH_TYPE_DECLARATIONS')) {    echo "Please define the SYMFONY_PATCH_TYPE_DECLARATIONS env var when running this script.\n";    exit(1);}$loader = require __DIR__.'/vendor/autoload.php';Symfony\Component\ErrorHandler\DebugClassLoader::enable();foreach ($loader->getClassMap() as $class => $file) {    switch (true) {        case false !== strpos($file = realpath($file), '/vendor/'):        case false !== strpos($file, '/src/path-to-exclude/'): // add as many as required            continue;    }    class_exists($class);}Symfony\Component\ErrorHandler\DebugClassLoader::checkClasses();```Commits-------bb11e62 [ErrorHandler] Turn return-type annotations into deprecations by default, add mode to turn them into native types