diff --git a/doc/tags/for.rst b/doc/tags/for.rst
index 549189b20..fdc41d678 100644
--- a/doc/tags/for.rst
+++ b/doc/tags/for.rst
@@ -45,7 +45,7 @@ The ``..`` operator can take any expression at both sides:
         * {{ letter }}
     {% endfor %}
 
-.. tip:
+.. tip::
 
     If you need a step different from 1, you can use the ``range`` function
     instead.
@@ -94,6 +94,21 @@ the :doc:`slice <../filters/slice>` filter:
         {% endfor %}
     </ul>
 
+Iterating over a String
+-----------------------
+
+To iterate over the characters of a string, use the
+:doc:`split <../filters/split>` filter:
+
+.. code-block:: html+twig
+
+    <h1>Characters</h1>
+    <ul>
+        {% for char in "諺 / ことわざ"|split('') -%}
+            <li>{{ char }}</li>
+        {%- endfor %}
+    </ul>
+
 Adding a Condition
 ------------------
 
diff --git a/doc/tags/index.rst b/doc/tags/index.rst
index b3c104080..692ca6094 100644
--- a/doc/tags/index.rst
+++ b/doc/tags/index.rst
@@ -21,6 +21,7 @@ Tags
     macro
     sandbox
     set
+    types
     use
     verbatim
     with
diff --git a/doc/tags/types.rst b/doc/tags/types.rst
new file mode 100644
index 000000000..389afc1fc
--- /dev/null
+++ b/doc/tags/types.rst
@@ -0,0 +1,42 @@
+``types``
+=========
+
+.. versionadded:: 3.13
+
+    The ``types`` tag was added in Twig 3.13. This tag is **experimental** and can change based on usage and feedback.
+
+The ``types`` tag declares the types of template variables.
+
+To do this, specify a :ref:`mapping <twig-expressions>` of names to their types as strings. 
+
+Here is how to declare that ``foo`` is a boolean, while ``bar`` is an integer (see note below):
+
+.. code-block:: twig
+
+    {% types {
+        foo: 'bool',
+        bar: 'int',
+    } %}
+
+You can declare variables as optional by adding the ``?`` suffix:
+
+.. code-block:: twig
+
+    {% types {
+        foo: 'bool',
+        bar?: 'int',
+    } %}
+
+By default, this tag does not affect the template compilation or runtime behavior.
+
+Its purpose is to enable designers and developers to document and specify the context's available
+and/or required variables. While Twig itself does not validate variables or their types, this tag enables extensions
+to do this.
+
+Additionally, :ref:`Twig extensions <creating_extensions>` can analyze these tags to perform compile-time and
+runtime analysis of templates.
+
+.. note::
+
+    The syntax for and contents of type strings are intentionally left out of scope. 
+    
diff --git a/src/Compiler.php b/src/Compiler.php
index 6aeb1d752..8310e4f6d 100644
--- a/src/Compiler.php
+++ b/src/Compiler.php
@@ -22,17 +22,16 @@ class Compiler
     private ?int $lastLine;
     private string $source;
     private int $indentation;
-    private Environment $env;
-    private array $debugInfo;
+    private array $debugInfo = [];
     private int $sourceOffset;
     private int $sourceLine;
-    private int $varNameSalt;
+    private int $varNameSalt = 0;
     private string|false $didUseEcho = false;
     private array $didUseEchoStack = [];
 
-    public function __construct(Environment $env)
-    {
-        $this->env = $env;
+    public function __construct(
+        private Environment $env,
+    ) {
         $this->reset();
     }
 
diff --git a/src/Environment.php b/src/Environment.php
index d6c6c81cb..5441157a5 100644
--- a/src/Environment.php
+++ b/src/Environment.php
@@ -112,7 +112,7 @@ class Environment
      *                   (default to -1 which means that all optimizations are enabled;
      *                   set it to 0 to disable).
      */
-    public function __construct(LoaderInterface $loader, $options = [])
+    public function __construct(LoaderInterface $loader, array $options = [])
     {
         $this->setLoader($loader);
 
diff --git a/src/ExpressionParser.php b/src/ExpressionParser.php
index fbedcc547..c116aab72 100644
--- a/src/ExpressionParser.php
+++ b/src/ExpressionParser.php
@@ -47,17 +47,15 @@ class ExpressionParser
     public const OPERATOR_LEFT = 1;
     public const OPERATOR_RIGHT = 2;
 
-    private Parser $parser;
-    private Environment $env;
     /** @var array<string, array{precedence: int, class: class-string<AbstractUnary>}> */
     private array $unaryOperators;
     /** @var array<string, array{precedence: int, class: class-string<AbstractBinary>, associativity: self::OPERATOR_*}> */
     private array $binaryOperators;
 
-    public function __construct(Parser $parser, Environment $env)
-    {
-        $this->parser = $parser;
-        $this->env = $env;
+    public function __construct(
+        private Parser $parser,
+        private Environment $env,
+    ) {
         $this->unaryOperators = $env->getUnaryOperators();
         $this->binaryOperators = $env->getBinaryOperators();
     }
diff --git a/src/Extension/CoreExtension.php b/src/Extension/CoreExtension.php
index 111a37fd4..f9996abc7 100644
--- a/src/Extension/CoreExtension.php
+++ b/src/Extension/CoreExtension.php
@@ -86,6 +86,7 @@ use Twig\TokenParser\ImportTokenParser;
 use Twig\TokenParser\IncludeTokenParser;
 use Twig\TokenParser\MacroTokenParser;
 use Twig\TokenParser\SetTokenParser;
+use Twig\TokenParser\TypesTokenParser;
 use Twig\TokenParser\UseTokenParser;
 use Twig\TokenParser\WithTokenParser;
 use Twig\TwigFilter;
@@ -186,6 +187,7 @@ final class CoreExtension extends AbstractExtension
             new ImportTokenParser(),
             new FromTokenParser(),
             new SetTokenParser(),
+            new TypesTokenParser(),
             new FlushTokenParser(),
             new DoTokenParser(),
             new EmbedTokenParser(),
@@ -1259,6 +1261,12 @@ final class CoreExtension extends AbstractExtension
     }
 
     /**
+     * @template TSequence
+     *
+     * @param TSequence $seq
+     *
+     * @return ($seq is iterable ? TSequence : array{})
+     *
      * @internal
      */
     public static function toArray($seq, $preserveKeys = true)
diff --git a/src/Extension/OptimizerExtension.php b/src/Extension/OptimizerExtension.php
index bf2cd7bf7..d3fe46a67 100644
--- a/src/Extension/OptimizerExtension.php
+++ b/src/Extension/OptimizerExtension.php
@@ -15,11 +15,9 @@ use Twig\NodeVisitor\OptimizerNodeVisitor;
 
 final class OptimizerExtension extends AbstractExtension
 {
-    private int $optimizers;
-
-    public function __construct(int $optimizers = -1)
-    {
-        $this->optimizers = $optimizers;
+    public function __construct(
+        private int $optimizers = -1,
+    ) {
     }
 
     public function getNodeVisitors(): array
diff --git a/src/Loader/ArrayLoader.php b/src/Loader/ArrayLoader.php
index a7cb64d1c..b4127e2d0 100644
--- a/src/Loader/ArrayLoader.php
+++ b/src/Loader/ArrayLoader.php
@@ -28,17 +28,12 @@ use Twig\Source;
  */
 final class ArrayLoader implements LoaderInterface
 {
-    /**
-     * @var array<string, string>
-     */
-    private array $templates = [];
-
     /**
      * @param array<string, string> $templates An array of templates (keys are the names, and values are the source code)
      */
-    public function __construct(array $templates = [])
-    {
-        $this->templates = $templates;
+    public function __construct(
+        private array $templates = [],
+    ) {
     }
 
     public function setTemplate(string $name, string $template): void
diff --git a/src/Loader/ChainLoader.php b/src/Loader/ChainLoader.php
index 1f0a6a393..deca5d50a 100644
--- a/src/Loader/ChainLoader.php
+++ b/src/Loader/ChainLoader.php
@@ -21,11 +21,6 @@ use Twig\Source;
  */
 final class ChainLoader implements LoaderInterface
 {
-    /**
-     * @var \Traversable<LoaderInterface>|LoaderInterface[]
-     */
-    private iterable $loaders = [];
-
     /**
      * @var array<string, bool>
      */
@@ -34,9 +29,9 @@ final class ChainLoader implements LoaderInterface
     /**
      * @param iterable<LoaderInterface> $loaders
      */
-    public function __construct(iterable $loaders = [])
-    {
-        $this->loaders = $loaders;
+    public function __construct(
+        private iterable $loaders = [],
+    ) {
     }
 
     public function addLoader(LoaderInterface $loader): void
diff --git a/src/Markup.php b/src/Markup.php
index 81f5ae7a5..950c68a29 100644
--- a/src/Markup.php
+++ b/src/Markup.php
@@ -19,7 +19,7 @@ namespace Twig;
 class Markup implements \Countable, \JsonSerializable, \Stringable
 {
     private string $content;
-    private string $charset;
+    private ?string $charset;
 
     public function __construct($content, $charset)
     {
diff --git a/src/Node/ModuleNode.php b/src/Node/ModuleNode.php
index c8c15da2f..856c2547c 100644
--- a/src/Node/ModuleNode.php
+++ b/src/Node/ModuleNode.php
@@ -108,7 +108,7 @@ final class ModuleNode extends Node
         $parent = $this->getNode('parent');
 
         $compiler
-            ->write("protected function doGetParent(array \$context)\n", "{\n")
+            ->write("protected function doGetParent(array \$context): bool|string|Template|TemplateWrapper\n", "{\n")
             ->indent()
             ->addDebugInfo($parent)
             ->write('return ')
@@ -153,7 +153,9 @@ final class ModuleNode extends Node
                 ->write("use Twig\Sandbox\SecurityNotAllowedFilterError;\n")
                 ->write("use Twig\Sandbox\SecurityNotAllowedFunctionError;\n")
                 ->write("use Twig\Source;\n")
-                ->write("use Twig\Template;\n\n")
+                ->write("use Twig\Template;\n")
+                ->write("use Twig\TemplateWrapper;\n")
+                ->write("\n")
             ;
         }
         $compiler
@@ -164,6 +166,9 @@ final class ModuleNode extends Node
             ->write("{\n")
             ->indent()
             ->write("private Source \$source;\n")
+            ->write("/**\n")
+            ->write(" * @var array<string, Template>\n")
+            ->write(" */\n")
             ->write("private array \$macros = [];\n\n")
         ;
     }
@@ -370,7 +375,7 @@ final class ModuleNode extends Node
             ->write("/**\n")
             ->write(" * @codeCoverageIgnore\n")
             ->write(" */\n")
-            ->write("public function getTemplateName()\n", "{\n")
+            ->write("public function getTemplateName(): string\n", "{\n")
             ->indent()
             ->write('return ')
             ->repr($this->getSourceContext()->getName())
@@ -427,7 +432,7 @@ final class ModuleNode extends Node
             ->write("/**\n")
             ->write(" * @codeCoverageIgnore\n")
             ->write(" */\n")
-            ->write("public function isTraitable()\n", "{\n")
+            ->write("public function isTraitable(): bool\n", "{\n")
             ->indent()
             ->write("return false;\n")
             ->outdent()
@@ -441,7 +446,7 @@ final class ModuleNode extends Node
             ->write("/**\n")
             ->write(" * @codeCoverageIgnore\n")
             ->write(" */\n")
-            ->write("public function getDebugInfo()\n", "{\n")
+            ->write("public function getDebugInfo(): array\n", "{\n")
             ->indent()
             ->write(\sprintf("return %s;\n", str_replace("\n", '', var_export(array_reverse($compiler->getDebugInfo(), true), true))))
             ->outdent()
@@ -452,7 +457,7 @@ final class ModuleNode extends Node
     protected function compileGetSourceContext(Compiler $compiler)
     {
         $compiler
-            ->write("public function getSourceContext()\n", "{\n")
+            ->write("public function getSourceContext(): Source\n", "{\n")
             ->indent()
             ->write('return new Source(')
             ->string($compiler->getEnvironment()->isDebug() ? $this->getSourceContext()->getCode() : '')
diff --git a/src/Node/TypesNode.php b/src/Node/TypesNode.php
new file mode 100644
index 000000000..c4e0f081b
--- /dev/null
+++ b/src/Node/TypesNode.php
@@ -0,0 +1,28 @@
+<?php
+
+namespace Twig\Node;
+
+use Twig\Attribute\YieldReady;
+use Twig\Compiler;
+
+/**
+ * Represents a types node.
+ *
+ * @author Jeroen Versteeg <jeroen@alisqi.com>
+ */
+#[YieldReady]
+class TypesNode extends Node
+{
+    /**
+     * @param array<string, array{type: string, optional: bool}> $types
+     */
+    public function __construct(array $types, int $lineno)
+    {
+        parent::__construct([], ['mapping' => $types], $lineno);
+    }
+
+    public function compile(Compiler $compiler): void
+    {
+        // Don't compile anything.
+    }
+}
diff --git a/src/NodeVisitor/OptimizerNodeVisitor.php b/src/NodeVisitor/OptimizerNodeVisitor.php
index 54bbf7cd1..2fb743ce1 100644
--- a/src/NodeVisitor/OptimizerNodeVisitor.php
+++ b/src/NodeVisitor/OptimizerNodeVisitor.php
@@ -51,18 +51,16 @@ final class OptimizerNodeVisitor implements NodeVisitorInterface
      * @var string[]
      */
     private array $loopsTargets = [];
-    private int $optimizers;
 
     /**
      * @param int $optimizers The optimizer mode
      */
-    public function __construct(int $optimizers = -1)
-    {
+    public function __construct(
+        private int $optimizers = -1,
+    ) {
         if ($optimizers > (self::OPTIMIZE_FOR)) {
             throw new \InvalidArgumentException(\sprintf('Optimizer mode "%s" is not valid.', $optimizers));
         }
-
-        $this->optimizers = $optimizers;
     }
 
     public function enterNode(Node $node, Environment $env): Node
diff --git a/src/Parser.php b/src/Parser.php
index 4ce372afd..5834d834c 100644
--- a/src/Parser.php
+++ b/src/Parser.php
@@ -53,7 +53,6 @@ class Parser
      * @var MacroNode[]
      */
     private array $macros;
-    private Environment $env;
     private array $importedSymbols;
     /**
      * @var Node[]
@@ -65,9 +64,9 @@ class Parser
     private array $embeddedTemplates = [];
     private int $varNameSalt = 0;
 
-    public function __construct(Environment $env)
-    {
-        $this->env = $env;
+    public function __construct(
+        private Environment $env,
+    ) {
     }
 
     public function getVarName(): string
diff --git a/src/Profiler/NodeVisitor/ProfilerNodeVisitor.php b/src/Profiler/NodeVisitor/ProfilerNodeVisitor.php
index 1b9d6f8e0..0a2a87f81 100644
--- a/src/Profiler/NodeVisitor/ProfilerNodeVisitor.php
+++ b/src/Profiler/NodeVisitor/ProfilerNodeVisitor.php
@@ -27,13 +27,12 @@ use Twig\Profiler\Profile;
  */
 final class ProfilerNodeVisitor implements NodeVisitorInterface
 {
-    private string $extensionName;
     private string $varName;
 
-    public function __construct(string $extensionName)
-    {
-        $this->extensionName = $extensionName;
-        $this->varName = \sprintf('__internal_%s', hash('xxh128', $extensionName));
+    public function __construct(
+        private string $extensionName,
+    ) {
+        $this->varName = \sprintf('__internal_%s', hash(\PHP_VERSION_ID < 80100 ? 'sha256' : 'xxh128', $extensionName));
     }
 
     public function enterNode(Node $node, Environment $env): Node
diff --git a/src/Profiler/Profile.php b/src/Profiler/Profile.php
index 042baaff6..57204f8d5 100644
--- a/src/Profiler/Profile.php
+++ b/src/Profiler/Profile.php
@@ -21,9 +21,6 @@ final class Profile implements \IteratorAggregate, \Serializable
     public const TEMPLATE = 'template';
     public const MACRO = 'macro';
 
-    private string $template;
-    private string $name;
-    private string $type;
     private array $starts = [];
     private array $ends = [];
     /**
@@ -31,10 +28,11 @@ final class Profile implements \IteratorAggregate, \Serializable
      */
     private array $profiles = [];
 
-    public function __construct(string $template = 'main', string $type = self::ROOT, string $name = 'main')
-    {
-        $this->template = $template;
-        $this->type = $type;
+    public function __construct(
+        private string $template = 'main',
+        private string $type = self::ROOT,
+        private string $name = 'main',
+    ) {
         $this->name = str_starts_with($name, '__internal_') ? 'INTERNAL' : $name;
         $this->enter();
     }
diff --git a/src/RuntimeLoader/ContainerRuntimeLoader.php b/src/RuntimeLoader/ContainerRuntimeLoader.php
index 6646cfbaa..89862b09f 100644
--- a/src/RuntimeLoader/ContainerRuntimeLoader.php
+++ b/src/RuntimeLoader/ContainerRuntimeLoader.php
@@ -23,11 +23,9 @@ use Psr\Container\ContainerInterface;
  */
 class ContainerRuntimeLoader implements RuntimeLoaderInterface
 {
-    private ContainerInterface $container;
-
-    public function __construct(ContainerInterface $container)
-    {
-        $this->container = $container;
+    public function __construct(
+        private ContainerInterface $container,
+    ) {
     }
 
     public function load(string $class): ?object
diff --git a/src/RuntimeLoader/FactoryRuntimeLoader.php b/src/RuntimeLoader/FactoryRuntimeLoader.php
index 5adfa395d..71950cfd2 100644
--- a/src/RuntimeLoader/FactoryRuntimeLoader.php
+++ b/src/RuntimeLoader/FactoryRuntimeLoader.php
@@ -18,17 +18,12 @@ namespace Twig\RuntimeLoader;
  */
 class FactoryRuntimeLoader implements RuntimeLoaderInterface
 {
-    /**
-     * @var array<string, callable(): object>
-     */
-    private array $map;
-
     /**
      * @param array<string, callable(): object> $map An array where keys are class names and values factory callables
      */
-    public function __construct(array $map = [])
-    {
-        $this->map = $map;
+    public function __construct(
+        private array $map = [],
+    ) {
     }
 
     public function load(string $class): ?object
diff --git a/src/Source.php b/src/Source.php
index 87427da94..0f626b62d 100644
--- a/src/Source.php
+++ b/src/Source.php
@@ -18,20 +18,16 @@ namespace Twig;
  */
 final class Source
 {
-    private string $code;
-    private string $name;
-    private string $path;
-
     /**
      * @param string $code The template source code
      * @param string $name The template logical name
      * @param string $path The filesystem path of the template if any
      */
-    public function __construct(string $code, string $name, string $path = '')
-    {
-        $this->code = $code;
-        $this->name = $name;
-        $this->path = $path;
+    public function __construct(
+        private string $code,
+        private string $name,
+        private string $path = '',
+    ) {
     }
 
     public function getCode(): string
diff --git a/src/Template.php b/src/Template.php
index d85c9fcf5..fa7c0065c 100644
--- a/src/Template.php
+++ b/src/Template.php
@@ -34,38 +34,33 @@ abstract class Template
 
     protected $parent;
     protected $parents = [];
-    protected $env;
     protected $blocks = [];
     protected $traits = [];
     protected $extensions = [];
     protected $sandbox;
 
-    public function __construct(Environment $env)
-    {
-        $this->env = $env;
+    public function __construct(
+        protected Environment $env,
+    ) {
         $this->extensions = $env->getExtensions();
     }
 
     /**
      * Returns the template name.
-     *
-     * @return string The template name
      */
-    abstract public function getTemplateName();
+    abstract public function getTemplateName(): string;
 
     /**
      * Returns debug information about the template.
      *
-     * @return array Debug information
+     * @return array<int, int> Debug information
      */
-    abstract public function getDebugInfo();
+    abstract public function getDebugInfo(): array;
 
     /**
      * Returns information about the original template source code.
-     *
-     * @return Source
      */
-    abstract public function getSourceContext();
+    abstract public function getSourceContext(): Source;
 
     /**
      * Auto-generated method to display the template with the given context.
@@ -111,12 +106,12 @@ abstract class Template
         return $this->parents[$parent];
     }
 
-    protected function doGetParent(array $context)
+    protected function doGetParent(array $context): bool|string|self|TemplateWrapper
     {
         return false;
     }
 
-    public function isTraitable()
+    public function isTraitable(): bool
     {
         return true;
     }
diff --git a/src/TemplateWrapper.php b/src/TemplateWrapper.php
index 45e1b4b93..c31f50161 100644
--- a/src/TemplateWrapper.php
+++ b/src/TemplateWrapper.php
@@ -18,19 +18,16 @@ namespace Twig;
  */
 final class TemplateWrapper
 {
-    private Environment $env;
-    private Template $template;
-
     /**
      * This method is for internal use only and should never be called
      * directly (use Twig\Environment::load() instead).
      *
      * @internal
      */
-    public function __construct(Environment $env, Template $template)
-    {
-        $this->env = $env;
-        $this->template = $template;
+    public function __construct(
+        private Environment $env,
+        private Template $template,
+    ) {
     }
 
     public function render(array $context = []): string
diff --git a/src/Token.php b/src/Token.php
index fe1738a99..6bbee7841 100644
--- a/src/Token.php
+++ b/src/Token.php
@@ -17,10 +17,6 @@ namespace Twig;
  */
 final class Token
 {
-    private $value;
-    private int $type;
-    private int $lineno;
-
     public const EOF_TYPE = -1;
     public const TEXT_TYPE = 0;
     public const BLOCK_START_TYPE = 1;
@@ -37,11 +33,11 @@ final class Token
     public const ARROW_TYPE = 12;
     public const SPREAD_TYPE = 13;
 
-    public function __construct(int $type, $value, int $lineno)
-    {
-        $this->type = $type;
-        $this->value = $value;
-        $this->lineno = $lineno;
+    public function __construct(
+        private int $type,
+        private $value,
+        private int $lineno,
+    ) {
     }
 
     public function __toString()
diff --git a/src/TokenParser/TypesTokenParser.php b/src/TokenParser/TypesTokenParser.php
new file mode 100644
index 000000000..b579fd0c0
--- /dev/null
+++ b/src/TokenParser/TypesTokenParser.php
@@ -0,0 +1,85 @@
+<?php
+
+/*
+ * This file is part of Twig.
+ *
+ * (c) Fabien Potencier
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Twig\TokenParser;
+
+use Twig\Error\SyntaxError;
+use Twig\Node\Node;
+use Twig\Node\TypesNode;
+use Twig\Token;
+use Twig\TokenStream;
+
+/**
+ * Declare variable types.
+ *
+ *  {% types {foo: 'int', bar?: 'string'} %}
+ *
+ * @author Jeroen Versteeg <jeroen@alisqi.com>
+ * @internal
+ */
+final class TypesTokenParser extends AbstractTokenParser
+{
+    public function parse(Token $token): Node
+    {
+        $stream = $this->parser->getStream();
+
+        $types = $this->parseSimpleMappingExpression($stream);
+
+        $stream->expect(Token::BLOCK_END_TYPE);
+
+        return new TypesNode($types, $token->getLine());
+    }
+
+    /**
+     * @return array<string, array{type: string, optional: bool}>
+     *
+     * @throws SyntaxError
+     */
+    private function parseSimpleMappingExpression(TokenStream $stream): array
+    {
+        $stream->expect(Token::PUNCTUATION_TYPE, '{', 'A mapping element was expected');
+
+        $types = [];
+
+        $first = true;
+        while (!$stream->test(Token::PUNCTUATION_TYPE, '}')) {
+            if (!$first) {
+                $stream->expect(Token::PUNCTUATION_TYPE, ',', 'A type string must be followed by a comma');
+
+                // trailing ,?
+                if ($stream->test(Token::PUNCTUATION_TYPE, '}')) {
+                    break;
+                }
+            }
+            $first = false;
+
+            $nameToken = $stream->expect(Token::NAME_TYPE);
+            $isOptional = $stream->nextIf(Token::PUNCTUATION_TYPE, '?') !== null;
+
+            $stream->expect(Token::PUNCTUATION_TYPE, ':', 'A type name must be followed by a colon (:)');
+
+            $valueToken = $stream->expect(Token::STRING_TYPE);
+
+            $types[$nameToken->getValue()] = [
+                'type'     => $valueToken->getValue(),
+                'optional' => $isOptional,
+            ];
+        }
+        $stream->expect(Token::PUNCTUATION_TYPE, '}', 'An opened mapping is not properly closed');
+
+        return $types;
+    }
+
+    public function getTag(): string
+    {
+        return 'types';
+    }
+}
diff --git a/src/TokenStream.php b/src/TokenStream.php
index 5dc234f69..b99efd04f 100644
--- a/src/TokenStream.php
+++ b/src/TokenStream.php
@@ -21,16 +21,15 @@ use Twig\Error\SyntaxError;
  */
 final class TokenStream
 {
-    /**
-     * @var Token[]
-     */
-    private array $tokens;
     private int $current = 0;
-    private Source $source;
 
-    public function __construct(array $tokens, ?Source $source = null)
-    {
-        $this->tokens = $tokens;
+    /**
+     * @param Token[] $tokens
+     */
+    public function __construct(
+        private array $tokens,
+        private ?Source $source = null,
+    ) {
         $this->source = $source ?: new Source('', '');
     }
 
diff --git a/src/Util/DeprecationCollector.php b/src/Util/DeprecationCollector.php
index af882257d..0ea26ed4b 100644
--- a/src/Util/DeprecationCollector.php
+++ b/src/Util/DeprecationCollector.php
@@ -20,11 +20,9 @@ use Twig\Source;
  */
 final class DeprecationCollector
 {
-    private Environment $twig;
-
-    public function __construct(Environment $twig)
-    {
-        $this->twig = $twig;
+    public function __construct(
+        private Environment $twig,
+    ) {
     }
 
     /**
diff --git a/tests/Fixtures/tags/for/for_on_strings.test b/tests/Fixtures/tags/for/for_on_strings.test
new file mode 100644
index 000000000..62d484269
--- /dev/null
+++ b/tests/Fixtures/tags/for/for_on_strings.test
@@ -0,0 +1,13 @@
+--TEST--
+"for" tag can iterate over a string via the "split" filter
+--TEMPLATE--
+{% set jp = "諺 / ことわざ" %}
+
+{% for letter in jp|split('') -%}
+    -{{- letter }}
+    {{- loop.last ? '.' }}
+{%- endfor %}
+--DATA--
+return []
+--EXPECT--
+-諺- -/- -こ-と-わ-ざ.
diff --git a/tests/Node/ModuleTest.php b/tests/Node/ModuleTest.php
index eef62f8f5..f3081dff9 100644
--- a/tests/Node/ModuleTest.php
+++ b/tests/Node/ModuleTest.php
@@ -23,6 +23,8 @@ use Twig\Node\Node;
 use Twig\Node\SetNode;
 use Twig\Node\TextNode;
 use Twig\Source;
+use Twig\Template;
+use Twig\TemplateWrapper;
 use Twig\Test\NodeTestCase;
 
 class ModuleTest extends NodeTestCase
@@ -73,11 +75,15 @@ use Twig\Sandbox\SecurityNotAllowedFilterError;
 use Twig\Sandbox\SecurityNotAllowedFunctionError;
 use Twig\Source;
 use Twig\Template;
+use Twig\TemplateWrapper;
 
 /* foo.twig */
 class __TwigTemplate_%x extends Template
 {
     private Source \$source;
+    /**
+     * @var array<string, Template>
+     */
     private array \$macros = [];
 
     public function __construct(Environment \$env)
@@ -103,7 +109,7 @@ class __TwigTemplate_%x extends Template
     /**
      * @codeCoverageIgnore
      */
-    public function getTemplateName()
+    public function getTemplateName(): string
     {
         return "foo.twig";
     }
@@ -111,12 +117,12 @@ class __TwigTemplate_%x extends Template
     /**
      * @codeCoverageIgnore
      */
-    public function getDebugInfo()
+    public function getDebugInfo(): array
     {
-        return array (  38 => 1,);
+        return array (  42 => 1,);
     }
 
-    public function getSourceContext()
+    public function getSourceContext(): Source
     {
         return new Source("", "foo.twig", "");
     }
@@ -145,11 +151,15 @@ use Twig\Sandbox\SecurityNotAllowedFilterError;
 use Twig\Sandbox\SecurityNotAllowedFunctionError;
 use Twig\Source;
 use Twig\Template;
+use Twig\TemplateWrapper;
 
 /* foo.twig */
 class __TwigTemplate_%x extends Template
 {
     private Source \$source;
+    /**
+     * @var array<string, Template>
+     */
     private array \$macros = [];
 
     public function __construct(Environment \$env)
@@ -162,7 +172,7 @@ class __TwigTemplate_%x extends Template
         ];
     }
 
-    protected function doGetParent(array \$context)
+    protected function doGetParent(array \$context): bool|string|Template|TemplateWrapper
     {
         // line 1
         return "layout.twig";
@@ -181,7 +191,7 @@ class __TwigTemplate_%x extends Template
     /**
      * @codeCoverageIgnore
      */
-    public function getTemplateName()
+    public function getTemplateName(): string
     {
         return "foo.twig";
     }
@@ -189,7 +199,7 @@ class __TwigTemplate_%x extends Template
     /**
      * @codeCoverageIgnore
      */
-    public function isTraitable()
+    public function isTraitable(): bool
     {
         return false;
     }
@@ -197,12 +207,12 @@ class __TwigTemplate_%x extends Template
     /**
      * @codeCoverageIgnore
      */
-    public function getDebugInfo()
+    public function getDebugInfo(): array
     {
-        return array (  44 => 1,  42 => 2,  35 => 1,);
+        return array (  48 => 1,  46 => 2,  39 => 1,);
     }
 
-    public function getSourceContext()
+    public function getSourceContext(): Source
     {
         return new Source("", "foo.twig", "");
     }
@@ -236,11 +246,15 @@ use Twig\Sandbox\SecurityNotAllowedFilterError;
 use Twig\Sandbox\SecurityNotAllowedFunctionError;
 use Twig\Source;
 use Twig\Template;
+use Twig\TemplateWrapper;
 
 /* foo.twig */
 class __TwigTemplate_%x extends Template
 {
     private Source \$source;
+    /**
+     * @var array<string, Template>
+     */
     private array \$macros = [];
 
     public function __construct(Environment \$env)
@@ -253,7 +267,7 @@ class __TwigTemplate_%x extends Template
         ];
     }
 
-    protected function doGetParent(array \$context)
+    protected function doGetParent(array \$context): bool|string|Template|TemplateWrapper
     {
         // line 2
         return \$this->loadTemplate(((true) ? ("foo") : ("foo")), "foo.twig", 2);
@@ -271,7 +285,7 @@ class __TwigTemplate_%x extends Template
     /**
      * @codeCoverageIgnore
      */
-    public function getTemplateName()
+    public function getTemplateName(): string
     {
         return "foo.twig";
     }
@@ -279,7 +293,7 @@ class __TwigTemplate_%x extends Template
     /**
      * @codeCoverageIgnore
      */
-    public function isTraitable()
+    public function isTraitable(): bool
     {
         return false;
     }
@@ -287,12 +301,12 @@ class __TwigTemplate_%x extends Template
     /**
      * @codeCoverageIgnore
      */
-    public function getDebugInfo()
+    public function getDebugInfo(): array
     {
-        return array (  44 => 2,  42 => 4,  35 => 2,);
+        return array (  48 => 2,  46 => 4,  39 => 2,);
     }
 
-    public function getSourceContext()
+    public function getSourceContext(): Source
     {
         return new Source("{{ foo }}", "foo.twig", "");
     }
diff --git a/tests/Node/TypesTest.php b/tests/Node/TypesTest.php
new file mode 100644
index 000000000..ff6c2dfac
--- /dev/null
+++ b/tests/Node/TypesTest.php
@@ -0,0 +1,43 @@
+<?php
+
+namespace Twig\Tests\Node;
+
+use Twig\Node\TypesNode;
+use Twig\Test\NodeTestCase;
+
+class TypesTest extends NodeTestCase
+{
+    private function getValidMapping(): array
+    {
+        // {foo: 'string', bar?: 'int'}
+        return [
+            'foo' => [
+                'type' => 'string',
+                'optional' => false,
+            ],
+            'bar' => [
+                'type' => 'int',
+                'optional' => true,
+            ]
+        ];
+    }
+
+    public function testConstructor()
+    {
+        $types = $this->getValidMapping();
+        $node = new TypesNode($types, 1);
+
+        $this->assertEquals($types, $node->getAttribute('mapping'));
+    }
+
+    public function getTests()
+    {
+        return [
+            // 1st test: Node shouldn't compile at all
+            [
+                new TypesNode($this->getValidMapping(), 1),
+                ''
+            ]
+        ];
+    }
+}
diff --git a/tests/TemplateTest.php b/tests/TemplateTest.php
index 18e196161..66437d2d1 100644
--- a/tests/TemplateTest.php
+++ b/tests/TemplateTest.php
@@ -21,6 +21,7 @@ use Twig\Sandbox\SecurityError;
 use Twig\Sandbox\SecurityPolicy;
 use Twig\Source;
 use Twig\Template;
+use Twig\TemplateWrapper;
 
 class TemplateTest extends TestCase
 {
@@ -425,22 +426,22 @@ class TemplateForTest extends Template
         return true;
     }
 
-    public function getTemplateName()
+    public function getTemplateName(): string
     {
         return $this->name;
     }
 
-    public function getDebugInfo()
+    public function getDebugInfo() : array
     {
         return [];
     }
 
-    public function getSourceContext()
+    public function getSourceContext() : Source
     {
         return new Source('', $this->getTemplateName());
     }
 
-    protected function doGetParent(array $context)
+    protected function doGetParent(array $context): bool|string|Template|TemplateWrapper
     {
         return false;
     }
diff --git a/tests/TokenParser/TypesTokenParserTest.php b/tests/TokenParser/TypesTokenParserTest.php
new file mode 100644
index 000000000..1d27d9d15
--- /dev/null
+++ b/tests/TokenParser/TypesTokenParserTest.php
@@ -0,0 +1,69 @@
+<?php
+
+namespace Twig\Tests\TokenParser;
+
+use PHPUnit\Framework\TestCase;
+use Twig\Environment;
+use Twig\Loader\ArrayLoader;
+use Twig\Parser;
+use Twig\Source;
+
+class TypesTokenParserTest extends TestCase
+{
+    /** @dataProvider getMappingTests */
+    public function testMappingParsing(string $template, array $expected): void
+    {
+        $env = new Environment(new ArrayLoader(), ['cache' => false, 'autoescape' => false]);
+        $stream = $env->tokenize($source = new Source($template, ''));
+        $parser = new Parser($env);
+
+        $typesNode = $parser->parse($stream)->getNode('body')->getNode('0');
+
+        self::assertEquals($expected, $typesNode->getAttribute('mapping'));
+    }
+
+    public function getMappingTests(): array
+    {
+        return [
+            // empty mapping
+            [
+                '{% types {} %}',
+                [],
+            ],
+
+            // simple
+            [
+                '{% types {foo: "bar"} %}',
+                [
+                    'foo' => ['type' => 'bar', 'optional' => false]
+                ],
+            ],
+
+            // trailing comma
+            [
+                '{% types {foo: "bar",} %}',
+                [
+                    'foo' => ['type' => 'bar', 'optional' => false]
+                ],
+            ],
+
+            // optional name
+            [
+                '{% types {foo?: "bar"} %}',
+                [
+                    'foo' => ['type' => 'bar', 'optional' => true]
+                ],
+            ],
+
+            // multiple pairs, duplicate values
+            [
+                '{% types {foo: "foo", bar?: "foo", baz: "baz"} %}',
+                [
+                    'foo' => ['type' => 'foo', 'optional' => false], 
+                    'bar' => ['type' => 'foo', 'optional' => true], 
+                    'baz' => ['type' => 'baz', 'optional' => false]
+                ],
+            ],
+        ];
+    }
+}