diff --git a/core/lib/Drupal/Core/Installer/Form/SiteConfigureForm.php b/core/lib/Drupal/Core/Installer/Form/SiteConfigureForm.php
index 750e967..b616960 100644
--- a/core/lib/Drupal/Core/Installer/Form/SiteConfigureForm.php
+++ b/core/lib/Drupal/Core/Installer/Form/SiteConfigureForm.php
@@ -239,9 +239,11 @@ public function buildForm(array $form, FormStateInterface $form_state) {
    * {@inheritdoc}
    */
   public function validateForm(array &$form, FormStateInterface $form_state) {
-    if ($error = user_validate_name($form_state->getValue(array('account', 'name')))) {
-      $form_state->setErrorByName('account][name', $error);
-    }
+    // HELP NEEDED: user_validate_name is broken with the new API, skip it until
+    // we can work out what is going on.
+//    if ($error = user_validate_name($form_state->getValue(array('account', 'name')))) {
+//      $form_state->setErrorByName('account][name', $error);
+//    }
   }
 
   /**
diff --git a/core/lib/Drupal/Core/TypedData/TypedDataManager.php b/core/lib/Drupal/Core/TypedData/TypedDataManager.php
old mode 100644
new mode 100755
index d42a3d2..143636d
--- a/core/lib/Drupal/Core/TypedData/TypedDataManager.php
+++ b/core/lib/Drupal/Core/TypedData/TypedDataManager.php
@@ -322,7 +322,7 @@ public function getValidator() {
       $this->validator = Validation::createValidatorBuilder()
         ->setMetadataFactory(new MetadataFactory())
         ->setTranslator(new DrupalTranslator())
-        ->setApiVersion(Validation::API_VERSION_2_4)
+        ->setApiVersion(Validation::API_VERSION_2_5)
         ->getValidator();
     }
     return $this->validator;
diff --git a/core/lib/Drupal/Core/TypedData/Validation/ClassMetadata.php b/core/lib/Drupal/Core/TypedData/Validation/ClassMetadata.php
new file mode 100755
index 0000000..e28c838
--- /dev/null
+++ b/core/lib/Drupal/Core/TypedData/Validation/ClassMetadata.php
@@ -0,0 +1,105 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\TypedData\Validation\ClassMetadata.
+ */
+
+namespace Drupal\Core\TypedData\Validation;
+
+use Drupal\Core\TypedData\ComplexDataInterface;
+use Drupal\Core\TypedData\ListInterface;
+use Symfony\Component\Validator\Mapping\ClassMetadataInterface;
+use Symfony\Component\Validator\ValidationVisitorInterface;
+
+/**
+ * Typed data implementation of the validator MetadataInterface.
+ */
+class ClassMetadata extends Metadata implements ClassMetadataInterface {
+
+  /**
+   * Overrides Metadata::accept().
+   */
+  public function accept(ValidationVisitorInterface $visitor, $typed_data, $group, $propertyPath) {
+    // To let all constraints properly handle empty structures, pass on NULL
+    // if the data structure is empty. That way existing NotNull or NotBlank
+    // constraints work as expected.
+    if ($typed_data->isEmpty()) {
+      $typed_data = NULL;
+    }
+    $visitor->visit($this, $typed_data, $group, $propertyPath);
+    $pathPrefix = isset($propertyPath) && $propertyPath !== '' ? $propertyPath . '.' : '';
+
+    if ($typed_data) {
+      foreach ($typed_data as $name => $data) {
+        $metadata = $this->factory->getMetadataFor($data, $name);
+        $metadata->accept($visitor, $data, $group, $pathPrefix . $name);
+      }
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function hasPropertyMetadata($property_name) {
+    try {
+      $exists = (bool)$this->getPropertyMetadata($property_name);
+    }
+    catch (\LogicException $e) {
+      $exists = FALSE;
+    }
+    return $exists;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getPropertyMetadata($property_name) {
+    if ($this->typedData instanceof ListInterface) {
+      // HELP NEEDED: Should this use $this->factory instead of creating a new instance?
+      return array(new Metadata($this->typedData, $property_name, new MetadataFactory()));
+    }
+    elseif ($this->typedData instanceof ComplexDataInterface) {
+      return array(new Metadata($this->typedData->get($property_name), $property_name, new MetadataFactory()));
+    }
+    else {
+      throw new \LogicException("There are no known properties.");
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getConstrainedProperties() {
+    if ($this->typedData instanceof ListInterface) {
+      return range(0, count($this->typedData) - 1);
+    }
+    elseif ($this->typedData instanceof ComplexDataInterface) {
+      return array_keys($this->typedData->getProperties());
+    }
+    else {
+      throw new \LogicException("There are no known properties.");
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getGroupSequence() {
+    return NULL;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function hasGroupSequence() {
+    return FALSE;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function isGroupSequenceProvider() {
+    return FALSE;
+  }
+}
diff --git a/core/lib/Drupal/Core/TypedData/Validation/Metadata.php b/core/lib/Drupal/Core/TypedData/Validation/Metadata.php
old mode 100644
new mode 100755
index 73bfc8b..acb0724
--- a/core/lib/Drupal/Core/TypedData/Validation/Metadata.php
+++ b/core/lib/Drupal/Core/TypedData/Validation/Metadata.php
@@ -8,8 +8,10 @@
 namespace Drupal\Core\TypedData\Validation;
 
 use Drupal\Core\TypedData\TypedDataInterface;
+use Symfony\Component\Validator\Mapping\CascadingStrategy;
+use Symfony\Component\Validator\Mapping\TraversalStrategy;
+use Symfony\Component\Validator\Mapping\PropertyMetadataInterface;
 use Symfony\Component\Validator\ValidationVisitorInterface;
-use Symfony\Component\Validator\PropertyMetadataInterface;
 
 /**
  * Typed data implementation of the validator MetadataInterface.
@@ -101,4 +103,32 @@ public function getPropertyValue($container) {
   public function getTypedData() {
     return $this->typedData;
   }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getClassName() {
+    return $this->typedData->getDataDefinition()->getClass();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getConstraints() {
+    return $this->typedData->getConstraints();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getCascadingStrategy() {
+    return CascadingStrategy::NONE;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getTraversalStrategy() {
+    return TraversalStrategy::IMPLICIT;
+  }
 }
diff --git a/core/lib/Drupal/Core/TypedData/Validation/MetadataFactory.php b/core/lib/Drupal/Core/TypedData/Validation/MetadataFactory.php
old mode 100644
new mode 100755
index 2858daf..4dbd2dc
--- a/core/lib/Drupal/Core/TypedData/Validation/MetadataFactory.php
+++ b/core/lib/Drupal/Core/TypedData/Validation/MetadataFactory.php
@@ -10,7 +10,7 @@
 use Drupal\Core\TypedData\ComplexDataInterface;
 use Drupal\Core\TypedData\ListInterface;
 use Drupal\Core\TypedData\TypedDataInterface;
-use Symfony\Component\Validator\MetadataFactoryInterface;
+use Symfony\Component\Validator\Mapping\Factory\MetadataFactoryInterface;
 
 /**
  * Typed data implementation of the validator MetadataFactoryInterface.
@@ -31,7 +31,7 @@ public function getMetadataFor($typed_data, $name = '') {
       throw new \InvalidArgumentException('The passed value must be a typed data object.');
     }
     $is_container = $typed_data instanceof ComplexDataInterface || $typed_data instanceof ListInterface;
-    $class = '\Drupal\Core\TypedData\Validation\\' . ($is_container ? 'PropertyContainerMetadata' : 'Metadata');
+    $class = '\Drupal\Core\TypedData\Validation\\' . ($is_container ? 'ClassMetadata' : 'Metadata');
     return new $class($typed_data, $name, $this);
   }
 
diff --git a/core/lib/Drupal/Core/Validation/Plugin/Validation/Constraint/ComplexDataConstraintValidator.php b/core/lib/Drupal/Core/Validation/Plugin/Validation/Constraint/ComplexDataConstraintValidator.php
old mode 100644
new mode 100755
index 31ffc5b..6cc5b27
--- a/core/lib/Drupal/Core/Validation/Plugin/Validation/Constraint/ComplexDataConstraintValidator.php
+++ b/core/lib/Drupal/Core/Validation/Plugin/Validation/Constraint/ComplexDataConstraintValidator.php
@@ -38,10 +38,14 @@ public function validate($value, Constraint $constraint) {
         $property = $property->getValue();
       }
       elseif ($property->isEmpty()) {
-        // @see \Drupal\Core\TypedData\Validation\PropertyContainerMetadata::accept();
+        // @see \Drupal\Core\TypedData\Validation\ClassMetadata::accept();
         $property = NULL;
       }
-      $this->context->validateValue($property, $constraints, $name, $group);
+
+      $this->context
+        ->getValidator()
+        ->inContext($this->context)
+        ->validate($property, $constraints, $group);
     }
   }
 }
diff --git a/core/modules/user/src/Plugin/Validation/Constraint/UserNameConstraintValidator.php b/core/modules/user/src/Plugin/Validation/Constraint/UserNameConstraintValidator.php
index 12d4fa3..887f50f 100644
--- a/core/modules/user/src/Plugin/Validation/Constraint/UserNameConstraintValidator.php
+++ b/core/modules/user/src/Plugin/Validation/Constraint/UserNameConstraintValidator.php
@@ -20,11 +20,17 @@ class UserNameConstraintValidator extends ConstraintValidator {
    * {@inheritdoc}
    */
   public function validate($items, Constraint $constraint) {
-    if (!isset($items) || !$items->value) {
+    // HELP NEEDED: Why has $items changed from an object
+    // (presumably TypedData\ListInterface) into an array?
+    if (!isset($items)) {
+      $this->context->addViolation($constraint->emptyMessage);
+      return;
+    }
+    $name = is_array($items) ? $items[0]['value'] : $items->first()->value;
+    if (!$name) {
       $this->context->addViolation($constraint->emptyMessage);
       return;
     }
-    $name = $items->first()->value;
     if (substr($name, 0, 1) == ' ') {
       $this->context->addViolation($constraint->spaceBeginMessage);
     }
diff --git a/core/vendor/symfony/validator/Symfony/Component/Validator/Validator/RecursiveContextualValidator.php b/core/vendor/symfony/validator/Symfony/Component/Validator/Validator/RecursiveContextualValidator.php
index 2da1887..c1cfbb5 100644
--- a/core/vendor/symfony/validator/Symfony/Component/Validator/Validator/RecursiveContextualValidator.php
+++ b/core/vendor/symfony/validator/Symfony/Component/Validator/Validator/RecursiveContextualValidator.php
@@ -419,7 +419,8 @@ private function validateEachObjectIn($collection, $propertyPath, array $groups,
 
             // Scalar and null values in the collection are ignored
             // (BC with Symfony < 2.5)
-            if (is_object($value)) {
+            // HELP NEEDED: String can't be validated, I think we're recursing one level too far
+            if (is_object($value) && ($value instanceof \Drupal\Core\TypedData\ComplexDataInterface || $value instanceof \Drupal\Core\TypedData\ListInterface)) {
                 $this->validateObject(
                     $value,
                     $propertyPath.'['.$key.']',