Fix return types

Author: nicolas-grekas

XPath/XPathExpr.php

@@ -46,7 +46,7 @@ public function getElement(): string
     /**
      * @return $this
      */
-    public function addCondition(string $condition): self
+    public function addCondition(string $condition): static
     {
         $this->condition = $this->condition ? sprintf('(%s) and (%s)', $this->condition, $condition) : $condition;
 
@@ -61,7 +61,7 @@ public function getCondition(): string
     /**
      * @return $this
      */
-    public function addNameTest(): self
+    public function addNameTest(): static
     {
         if ('*' !== $this->element) {
             $this->addCondition('name() = '.Translator::getXpathLiteral($this->element));
@@ -74,7 +74,7 @@ public function addNameTest(): self
     /**
      * @return $this
      */
-    public function addStarPrefix(): self
+    public function addStarPrefix(): static
     {
         $this->path .= '*/';