Merge branch '4.2'

* 4.2:
  [HttpFoundation] fix tests
  [Routing] fix trailing slash matching with empty-matching trailing vars
  [Routing] fix matching trailing vars with defaults
  [Validator] fix LegacyTranslatorProxy
  call method with Translator component only
  bumped Symfony version to 4.2.8
  updated VERSION for 4.2.7
  updated CHANGELOG for 4.2.7
  bumped Symfony version to 3.4.27
  updated VERSION for 3.4.26
  updated CHANGELOG for 3.4.26

Author: nicolas-grekas

Util/LegacyTranslatorProxy.php

@@ -22,15 +22,26 @@ class LegacyTranslatorProxy implements LegacyTranslatorInterface, TranslatorInte
 {
     private $translator;
 
-    public function __construct(TranslatorInterface $translator)
+    /**
+     * @param LegacyTranslatorInterface|TranslatorInterface $translator
+     */
+    public function __construct($translator)
     {
-        if (!$translator instanceof LocaleAwareInterface) {
+        if ($translator instanceof LegacyTranslatorInterface) {
+            // no-op
+        } elseif (!$translator instanceof TranslatorInterface) {
+            throw new \InvalidArgumentException(sprintf('The translator passed to "%s()" must implement "%s" or "%s".', __METHOD__, TranslatorInterface::class, LegacyTranslatorInterface::class));
+        } elseif (!$translator instanceof LocaleAwareInterface) {
             throw new \InvalidArgumentException(sprintf('The translator passed to "%s()" must implement "%s".', __METHOD__, LocaleAwareInterface::class));
         }
+
         $this->translator = $translator;
     }
 
-    public function getTranslator(): TranslatorInterface
+    /**
+     * @return LegacyTranslatorInterface|TranslatorInterface
+     */
+    public function getTranslator()
     {
         return $this->translator;
     }