minor #16211 [ExpressionLanguage] marked node classes as being internal (fabpot)

This PR was merged into the 2.8 branch.

Discussion
----------

[ExpressionLanguage] marked node classes as being internal

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | n/a
| License       | MIT
| Doc PR        | n/a

Adds `@internal` on some classes, would it make sense to also make them final?

Commits
-------

7d6bc48 [ExpressionLanguage] marked node classes as being internal

src/Symfony/Component/ExpressionLanguage/Node/ArgumentsNode.php

@@ -13,6 +13,11 @@ namespace Symfony\Component\ExpressionLanguage\Node;
 
 use Symfony\Component\ExpressionLanguage\Compiler;
 
+/**
+ * @author Fabien Potencier <fabien@symfony.com>
+ *
+ * @internal
+ */
 class ArgumentsNode extends ArrayNode
 {
     public function compile(Compiler $compiler)

src/Symfony/Component/ExpressionLanguage/Node/ArrayNode.php

@@ -13,6 +13,11 @@ namespace Symfony\Component\ExpressionLanguage\Node;
 
 use Symfony\Component\ExpressionLanguage\Compiler;
 
+/**
+ * @author Fabien Potencier <fabien@symfony.com>
+ *
+ * @internal
+ */
 class ArrayNode extends Node
 {
     protected $index;

src/Symfony/Component/ExpressionLanguage/Node/BinaryNode.php

@@ -13,6 +13,11 @@ namespace Symfony\Component\ExpressionLanguage\Node;
 
 use Symfony\Component\ExpressionLanguage\Compiler;
 
+/**
+ * @author Fabien Potencier <fabien@symfony.com>
+ *
+ * @internal
+ */
 class BinaryNode extends Node
 {
     private static $operators = array(

src/Symfony/Component/ExpressionLanguage/Node/ConditionalNode.php

@@ -13,6 +13,11 @@ namespace Symfony\Component\ExpressionLanguage\Node;
 
 use Symfony\Component\ExpressionLanguage\Compiler;
 
+/**
+ * @author Fabien Potencier <fabien@symfony.com>
+ *
+ * @internal
+ */
 class ConditionalNode extends Node
 {
     public function __construct(Node $expr1, Node $expr2, Node $expr3)

src/Symfony/Component/ExpressionLanguage/Node/ConstantNode.php

@@ -13,6 +13,11 @@ namespace Symfony\Component\ExpressionLanguage\Node;
 
 use Symfony\Component\ExpressionLanguage\Compiler;
 
+/**
+ * @author Fabien Potencier <fabien@symfony.com>
+ *
+ * @internal
+ */
 class ConstantNode extends Node
 {
     public function __construct($value)

src/Symfony/Component/ExpressionLanguage/Node/FunctionNode.php

@@ -13,6 +13,11 @@ namespace Symfony\Component\ExpressionLanguage\Node;
 
 use Symfony\Component\ExpressionLanguage\Compiler;
 
+/**
+ * @author Fabien Potencier <fabien@symfony.com>
+ *
+ * @internal
+ */
 class FunctionNode extends Node
 {
     public function __construct($name, Node $arguments)

src/Symfony/Component/ExpressionLanguage/Node/GetAttrNode.php

@@ -13,6 +13,11 @@ namespace Symfony\Component\ExpressionLanguage\Node;
 
 use Symfony\Component\ExpressionLanguage\Compiler;
 
+/**
+ * @author Fabien Potencier <fabien@symfony.com>
+ *
+ * @internal
+ */
 class GetAttrNode extends Node
 {
     const PROPERTY_CALL = 1;

src/Symfony/Component/ExpressionLanguage/Node/NameNode.php

@@ -13,6 +13,11 @@ namespace Symfony\Component\ExpressionLanguage\Node;
 
 use Symfony\Component\ExpressionLanguage\Compiler;
 
+/**
+ * @author Fabien Potencier <fabien@symfony.com>
+ *
+ * @internal
+ */
 class NameNode extends Node
 {
     public function __construct($name)

src/Symfony/Component/ExpressionLanguage/Node/UnaryNode.php

@@ -13,6 +13,11 @@ namespace Symfony\Component\ExpressionLanguage\Node;
 
 use Symfony\Component\ExpressionLanguage\Compiler;
 
+/**
+ * @author Fabien Potencier <fabien@symfony.com>
+ *
+ * @internal
+ */
 class UnaryNode extends Node
 {
     private static $operators = array(