Seal the AbstractLiteral/ListLiteral hierarchy (@internal) (#96)

src/AbstractLiteral.php

@@ -4,6 +4,15 @@
 
 namespace Eventjet\Ausdruck;
 
+/**
+ * The base for literal nodes — expressions whose value is known without a scope. The {@see self::value()} extension
+ * point exists only so a literal can materialize itself and its nested literals ({@see ListLiteral}, {@see StructLiteral})
+ * without going through {@see Expression::evaluate()}; the three subclasses that need it all live in this package, so
+ * nothing outside it has reason to add a fourth.
+ *
+ * @internal
+ * @psalm-internal Eventjet\Ausdruck
+ */
 abstract class AbstractLiteral extends Expression
 {
     abstract public function value(): mixed;

src/ListLiteral.php

@@ -12,6 +12,10 @@
 use function implode;
 use function sprintf;
 
+/**
+ * @internal
+ * @psalm-internal Eventjet\Ausdruck
+ */
 final class ListLiteral extends AbstractLiteral
 {
     /**