Merge branch '7.1' into 7.2

* 7.1:
  [TypeInfo] Add documentation

Author: javiereguiluz

components/type_info.rst

@@ -0,0 +1,75 @@
+The TypeInfo Component
+======================
+
+The TypeInfo component extracts type information from PHP elements like properties,
+arguments and return types.
+
+This component provides:
+
+* A powerful ``Type`` definition that can handle unions, intersections, and generics
+  (and can be extended to support more types in the future);
+* A way to get types from PHP elements such as properties, method arguments,
+  return types, and raw strings.
+
+.. caution::
+
+    This component is :doc:`experimental </contributing/code/experimental>` and
+    could be changed at any time without prior notice.
+
+Installation
+------------
+
+.. code-block:: terminal
+
+    $ composer require symfony/type-info
+
+.. include:: /components/require_autoload.rst.inc
+
+Usage
+-----
+
+This component gives you a :class:`Symfony\\Component\\TypeInfo\\Type` object that
+represents the PHP type of anything you built or asked to resolve.
+
+There are two ways to use this component. First one is to create a type manually thanks
+to the :class:`Symfony\\Component\\TypeInfo\\Type` static methods as following::
+
+    use Symfony\Component\TypeInfo\Type;
+
+    Type::int();
+    Type::nullable(Type::string());
+    Type::generic(Type::object(Collection::class), Type::int());
+    Type::list(Type::bool());
+    Type::intersection(Type::object(\Stringable::class), Type::object(\Iterator::class));
+
+    // Many others are available and can be
+    // found in Symfony\Component\TypeInfo\TypeFactoryTrait
+
+The second way of using the component is to use ``TypeInfo`` to resolve a type
+based on reflection or a simple string::
+
+    use Symfony\Component\TypeInfo\Type;
+    use Symfony\Component\TypeInfo\TypeResolver\TypeResolver;
+
+    // Instantiate a new resolver
+    $typeResolver = TypeResolver::create();
+
+    // Then resolve types for any subject
+    $typeResolver->resolve(new \ReflectionProperty(Dummy::class, 'id')); // returns an "int" Type instance
+    $typeResolver->resolve('bool'); // returns a "bool" Type instance
+
+    // Types can be instantiated thanks to static factories
+    $type = Type::list(Type::nullable(Type::bool()));
+
+    // Type instances have several helper methods
+    $type->getBaseType() // returns an "array" Type instance
+    $type->getCollectionKeyType(); // returns an "int" Type instance
+    $type->getCollectionValueType()->isNullable(); // returns true
+
+Each of this calls will return you a ``Type`` instance that corresponds to the
+static method used. You can also resolve types from a string (as shown in the
+``bool`` parameter of the previous example)
+
+.. note::
+
+    To support raw string resolving, you need to install ``phpstan/phpdoc-parser`` package.