diff --git a/composer.json b/composer.json
index dc21a469..f92f4431 100644
--- a/composer.json
+++ b/composer.json
@@ -47,7 +47,8 @@
         },
         "classmap": [
             "tests/src/Type/data",
-            "tests/src/Rules/data"
+            "tests/src/Rules/data",
+            "tests/src/Generics/data"
         ]
     },
     "extra": {
diff --git a/phpstan.neon b/phpstan.neon
index 24f9b845..4230bd42 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -12,6 +12,7 @@ parameters:
 		- tests/src
 	excludePaths:
 		-  tests/src/data/*.php
+		-  tests/src/Generics/data/*.php
 		-  tests/src/Type/data/*.php
 		-  tests/src/Rules/data/*.php
 		-  tests/src/DeprecatedScope/data/*.php
diff --git a/stubs/Drupal/Component/Plugin/DependentPluginInterface.stub b/stubs/Drupal/Component/Plugin/DependentPluginInterface.stub
new file mode 100644
index 00000000..b8ef9160
--- /dev/null
+++ b/stubs/Drupal/Component/Plugin/DependentPluginInterface.stub
@@ -0,0 +1,7 @@
+<?php
+
+namespace Drupal\Component\Plugin;
+
+interface DependentPluginInterface {
+
+}
diff --git a/stubs/Drupal/Component/Plugin/DerivativeInspectionInterface.stub b/stubs/Drupal/Component/Plugin/DerivativeInspectionInterface.stub
new file mode 100644
index 00000000..bf539fe1
--- /dev/null
+++ b/stubs/Drupal/Component/Plugin/DerivativeInspectionInterface.stub
@@ -0,0 +1,7 @@
+<?php
+
+namespace Drupal\Component\Plugin;
+
+interface DerivativeInspectionInterface {
+
+}
diff --git a/stubs/Drupal/Component/Plugin/PluginBase.stub b/stubs/Drupal/Component/Plugin/PluginBase.stub
new file mode 100644
index 00000000..fab12b46
--- /dev/null
+++ b/stubs/Drupal/Component/Plugin/PluginBase.stub
@@ -0,0 +1,7 @@
+<?php
+
+namespace Drupal\Component\Plugin;
+
+abstract class PluginBase implements PluginInspectionInterface, DerivativeInspectionInterface {
+
+}
diff --git a/stubs/Drupal/Core/Field/EntityReferenceFieldItemList.stub b/stubs/Drupal/Core/Field/EntityReferenceFieldItemList.stub
new file mode 100644
index 00000000..70477aae
--- /dev/null
+++ b/stubs/Drupal/Core/Field/EntityReferenceFieldItemList.stub
@@ -0,0 +1,15 @@
+<?php
+
+namespace Drupal\Core\Field;
+
+use Drupal\Core\Entity\EntityInterface;
+use Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem;
+
+/**
+ * @template T of EntityInterface
+ * @extends FieldItemList<EntityReferenceItem<T>>
+ * @implements EntityReferenceFieldItemListInterface<T>
+ */
+class EntityReferenceFieldItemList extends FieldItemList implements EntityReferenceFieldItemListInterface {
+
+}
\ No newline at end of file
diff --git a/stubs/Drupal/Core/Field/FieldItemList.stub b/stubs/Drupal/Core/Field/FieldItemList.stub
index 8545f092..be75341c 100644
--- a/stubs/Drupal/Core/Field/FieldItemList.stub
+++ b/stubs/Drupal/Core/Field/FieldItemList.stub
@@ -5,16 +5,15 @@ namespace Drupal\Core\Field;
 use Drupal\Core\TypedData\Plugin\DataType\ItemList;
 
 /**
- * @template T of \Drupal\Core\Field\FieldItemInterface
+ * @template T of FieldItemInterface
  * @extends ItemList<T>
  * @implements FieldItemListInterface<T>
  */
 class FieldItemList extends ItemList implements FieldItemListInterface {
 
   /**
-   * @return \Drupal\Core\Field\FieldItemInterface
+   * @return T
    */
-  protected function createItem(int $offset = 0, ?mixed $value = NULL): \Drupal\Core\Field\FieldItemInterface {
-  }
+  protected function createItem(int $offset = 0, mixed $value = NULL): FieldItemInterface {}
 
 }
diff --git a/stubs/Drupal/Core/Field/FormatterBase.stub b/stubs/Drupal/Core/Field/FormatterBase.stub
new file mode 100644
index 00000000..bf2965db
--- /dev/null
+++ b/stubs/Drupal/Core/Field/FormatterBase.stub
@@ -0,0 +1,34 @@
+<?php
+
+namespace Drupal\Core\Field;
+
+use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
+
+/**
+ * @template T of FieldItemListInterface
+ * @implements FormatterInterface<T>
+ */
+abstract class FormatterBase extends PluginSettingsBase implements FormatterInterface, ContainerFactoryPluginInterface {
+
+  /**
+   * @param array<T> $entities_items
+   */
+  public function prepareView(array $entities_items): void {}
+
+  /**
+   * @param T $items
+   * @param string|null $langcode
+   *
+   * @return array<int|string, mixed>
+   */
+  public function view(FieldItemListInterface $items, $langcode = NULL) {}
+
+  /**
+   * @param T $items
+   * @param string $langcode
+   *
+   * @return array<int, array<int|string, mixed>>
+   */
+  public function viewElements(FieldItemListInterface $items, $langcode) {}
+
+}
diff --git a/stubs/Drupal/Core/Field/FormatterInterface.stub b/stubs/Drupal/Core/Field/FormatterInterface.stub
new file mode 100644
index 00000000..ae8efa55
--- /dev/null
+++ b/stubs/Drupal/Core/Field/FormatterInterface.stub
@@ -0,0 +1,31 @@
+<?php
+
+namespace Drupal\Core\Field;
+
+/**
+ * @template T of FieldItemListInterface
+ */
+interface FormatterInterface extends PluginSettingsInterface {
+
+  /**
+   * @param array<T> $entities_items
+   */
+  public function prepareView(array $entities_items): void;
+
+  /**
+   * @param T $items
+   * @param string|null $langcode
+   *
+   * @return array<int|string, mixed>
+   */
+  public function view(FieldItemListInterface $items, $langcode = NULL);
+
+  /**
+   * @param T $items
+   * @param string $langcode
+   *
+   * @return array<int, array<int|string, mixed>>
+   */
+  public function viewElements(FieldItemListInterface $items, $langcode);
+
+}
diff --git a/stubs/Drupal/Core/Field/Plugin/Field/FieldFormatter/EntityReferenceFormatterBase.stub b/stubs/Drupal/Core/Field/Plugin/Field/FieldFormatter/EntityReferenceFormatterBase.stub
new file mode 100644
index 00000000..2c482dad
--- /dev/null
+++ b/stubs/Drupal/Core/Field/Plugin/Field/FieldFormatter/EntityReferenceFormatterBase.stub
@@ -0,0 +1,37 @@
+<?php
+
+namespace Drupal\Core\Field\Plugin\Field\FieldFormatter;
+
+use Drupal\Core\Entity\EntityInterface;
+use Drupal\Core\Field\EntityReferenceFieldItemList;
+use Drupal\Core\Field\FieldItemListInterface;
+use Drupal\Core\Field\FormatterBase;
+
+/**
+ * @template T of EntityInterface
+ * @extends FormatterBase<EntityReferenceFieldItemList<T>>
+ */
+abstract class EntityReferenceFormatterBase extends FormatterBase {
+
+  /**
+   * @param array<EntityReferenceFieldItemList<T>> $entities_items
+   */
+  public function prepareView(array $entities_items): void {}
+
+  /**
+   * @param EntityReferenceFieldItemList<T> $items
+   * @param string|null $langcode
+   *
+   * @return array<int|string, mixed>
+   */
+  public function view(FieldItemListInterface $items, $langcode = NULL) {}
+
+  /**
+   * @param EntityReferenceFieldItemList<T> $items
+   * @param string $langcode
+   *
+   * @return array<int, array<int|string, mixed>>
+   */
+  public function viewElements(FieldItemListInterface $items, $langcode) {}
+
+}
\ No newline at end of file
diff --git a/stubs/Drupal/Core/Field/PluginSettingsBase.stub b/stubs/Drupal/Core/Field/PluginSettingsBase.stub
new file mode 100644
index 00000000..e3d3d778
--- /dev/null
+++ b/stubs/Drupal/Core/Field/PluginSettingsBase.stub
@@ -0,0 +1,10 @@
+<?php
+
+namespace Drupal\Core\Field;
+
+use Drupal\Component\Plugin\DependentPluginInterface;
+use Drupal\Core\Plugin\PluginBase;
+
+abstract class PluginSettingsBase extends PluginBase implements PluginSettingsInterface, DependentPluginInterface {
+
+}
diff --git a/stubs/Drupal/Core/Field/PluginSettingsInterface.stub b/stubs/Drupal/Core/Field/PluginSettingsInterface.stub
new file mode 100644
index 00000000..bda09167
--- /dev/null
+++ b/stubs/Drupal/Core/Field/PluginSettingsInterface.stub
@@ -0,0 +1,10 @@
+<?php
+
+namespace Drupal\Core\Field;
+
+use Drupal\Component\Plugin\PluginInspectionInterface;
+use Drupal\Core\Config\Entity\ThirdPartySettingsInterface;
+
+interface PluginSettingsInterface extends PluginInspectionInterface, ThirdPartySettingsInterface {
+
+}
diff --git a/stubs/Drupal/Core/Plugin/ContainerFactoryPluginInterface.stub b/stubs/Drupal/Core/Plugin/ContainerFactoryPluginInterface.stub
new file mode 100644
index 00000000..daffdfd0
--- /dev/null
+++ b/stubs/Drupal/Core/Plugin/ContainerFactoryPluginInterface.stub
@@ -0,0 +1,7 @@
+<?php
+
+namespace Drupal\Core\Plugin;
+
+interface ContainerFactoryPluginInterface {
+
+}
diff --git a/stubs/Drupal/Core/Plugin/PluginBase.stub b/stubs/Drupal/Core/Plugin/PluginBase.stub
new file mode 100644
index 00000000..151d13f7
--- /dev/null
+++ b/stubs/Drupal/Core/Plugin/PluginBase.stub
@@ -0,0 +1,9 @@
+<?php
+
+namespace Drupal\Core\Plugin;
+
+use Drupal\Component\Plugin\PluginBase as ComponentPluginBase;
+
+abstract class PluginBase extends ComponentPluginBase {
+
+}
diff --git a/tests/src/Generics/EntityReferenceFieldItemListGenericTest.php b/tests/src/Generics/EntityReferenceFieldItemListGenericTest.php
new file mode 100644
index 00000000..b40bf540
--- /dev/null
+++ b/tests/src/Generics/EntityReferenceFieldItemListGenericTest.php
@@ -0,0 +1,33 @@
+<?php
+
+declare(strict_types=1);
+
+namespace mglaman\PHPStanDrupal\Tests\Generics;
+
+use mglaman\PHPStanDrupal\Tests\AdditionalConfigFilesTrait;
+use PHPStan\Testing\TypeInferenceTestCase;
+
+final class EntityReferenceFieldItemListGenericTest extends TypeInferenceTestCase
+{
+    use AdditionalConfigFilesTrait;
+
+    public static function dataFileAsserts(): iterable
+    {
+        yield from self::gatherAssertTypes(__DIR__ . '/data/entity-reference-field-item-list.php');
+    }
+
+    /**
+     * @dataProvider dataFileAsserts
+     * @param string $assertType
+     * @param string $file
+     * @param mixed ...$args
+     */
+    public function testFileAsserts(
+        string $assertType,
+        string $file,
+        ...$args
+    ): void
+    {
+        $this->assertFileAsserts($assertType, $file, ...$args);
+    }
+}
diff --git a/tests/src/Generics/EntityReferenceFormatterBaseGenericTest.php b/tests/src/Generics/EntityReferenceFormatterBaseGenericTest.php
new file mode 100644
index 00000000..d39aba3f
--- /dev/null
+++ b/tests/src/Generics/EntityReferenceFormatterBaseGenericTest.php
@@ -0,0 +1,33 @@
+<?php
+
+declare(strict_types=1);
+
+namespace mglaman\PHPStanDrupal\Tests\Generics;
+
+use mglaman\PHPStanDrupal\Tests\AdditionalConfigFilesTrait;
+use PHPStan\Testing\TypeInferenceTestCase;
+
+final class EntityReferenceFormatterBaseGenericTest extends TypeInferenceTestCase
+{
+    use AdditionalConfigFilesTrait;
+
+    public static function dataFileAsserts(): iterable
+    {
+        yield from self::gatherAssertTypes(__DIR__ . '/data/entity-reference-formatter-base.php');
+    }
+
+    /**
+     * @dataProvider dataFileAsserts
+     * @param string $assertType
+     * @param string $file
+     * @param mixed ...$args
+     */
+    public function testFileAsserts(
+        string $assertType,
+        string $file,
+        ...$args
+    ): void
+    {
+        $this->assertFileAsserts($assertType, $file, ...$args);
+    }
+}
diff --git a/tests/src/Generics/EntityReferenceItemGenericTest.php b/tests/src/Generics/EntityReferenceItemGenericTest.php
new file mode 100644
index 00000000..964a5b99
--- /dev/null
+++ b/tests/src/Generics/EntityReferenceItemGenericTest.php
@@ -0,0 +1,33 @@
+<?php
+
+declare(strict_types=1);
+
+namespace mglaman\PHPStanDrupal\Tests\Generics;
+
+use mglaman\PHPStanDrupal\Tests\AdditionalConfigFilesTrait;
+use PHPStan\Testing\TypeInferenceTestCase;
+
+final class EntityReferenceItemGenericTest extends TypeInferenceTestCase
+{
+    use AdditionalConfigFilesTrait;
+
+    public static function dataFileAsserts(): iterable
+    {
+        yield from self::gatherAssertTypes(__DIR__ . '/data/entity-reference-item.php');
+    }
+
+    /**
+     * @dataProvider dataFileAsserts
+     * @param string $assertType
+     * @param string $file
+     * @param mixed ...$args
+     */
+    public function testFileAsserts(
+        string $assertType,
+        string $file,
+        ...$args
+    ): void
+    {
+        $this->assertFileAsserts($assertType, $file, ...$args);
+    }
+}
diff --git a/tests/src/Generics/FormatterBaseGenericTest.php b/tests/src/Generics/FormatterBaseGenericTest.php
new file mode 100644
index 00000000..1536bf9f
--- /dev/null
+++ b/tests/src/Generics/FormatterBaseGenericTest.php
@@ -0,0 +1,33 @@
+<?php
+
+declare(strict_types=1);
+
+namespace mglaman\PHPStanDrupal\Tests\Generics;
+
+use mglaman\PHPStanDrupal\Tests\AdditionalConfigFilesTrait;
+use PHPStan\Testing\TypeInferenceTestCase;
+
+final class FormatterBaseGenericTest extends TypeInferenceTestCase
+{
+    use AdditionalConfigFilesTrait;
+
+    public static function dataFileAsserts(): iterable
+    {
+        yield from self::gatherAssertTypes(__DIR__ . '/data/formatter-base.php');
+    }
+
+    /**
+     * @dataProvider dataFileAsserts
+     * @param string $assertType
+     * @param string $file
+     * @param mixed ...$args
+     */
+    public function testFileAsserts(
+        string $assertType,
+        string $file,
+        ...$args
+    ): void
+    {
+        $this->assertFileAsserts($assertType, $file, ...$args);
+    }
+}
diff --git a/tests/src/Generics/FormatterInterfaceGenericTest.php b/tests/src/Generics/FormatterInterfaceGenericTest.php
new file mode 100644
index 00000000..2e5dacb6
--- /dev/null
+++ b/tests/src/Generics/FormatterInterfaceGenericTest.php
@@ -0,0 +1,33 @@
+<?php
+
+declare(strict_types=1);
+
+namespace mglaman\PHPStanDrupal\Tests\Generics;
+
+use mglaman\PHPStanDrupal\Tests\AdditionalConfigFilesTrait;
+use PHPStan\Testing\TypeInferenceTestCase;
+
+final class FormatterInterfaceGenericTest extends TypeInferenceTestCase
+{
+    use AdditionalConfigFilesTrait;
+
+    public static function dataFileAsserts(): iterable
+    {
+        yield from self::gatherAssertTypes(__DIR__ . '/data/formatter-interface.php');
+    }
+
+    /**
+     * @dataProvider dataFileAsserts
+     * @param string $assertType
+     * @param string $file
+     * @param mixed ...$args
+     */
+    public function testFileAsserts(
+        string $assertType,
+        string $file,
+        ...$args
+    ): void
+    {
+        $this->assertFileAsserts($assertType, $file, ...$args);
+    }
+}
diff --git a/tests/src/Generics/data/entity-reference-field-item-list.php b/tests/src/Generics/data/entity-reference-field-item-list.php
new file mode 100644
index 00000000..bc3bb0ee
--- /dev/null
+++ b/tests/src/Generics/data/entity-reference-field-item-list.php
@@ -0,0 +1,59 @@
+<?php
+
+namespace DrupalEntityReferenceFieldItemListGeneric;
+
+use Drupal\Core\Field\EntityReferenceFieldItemList;
+use Drupal\node\NodeInterface;
+use function PHPStan\Testing\assertType;
+
+function defaultItemList(EntityReferenceFieldItemList $items): void {
+    assertType('Drupal\Core\Field\EntityReferenceFieldItemList', $items);
+    assertType('Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem<Drupal\Core\Entity\EntityInterface>|null', $items->first());
+    assertType('Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem<Drupal\Core\Entity\EntityInterface>|null', $items->get(0));
+    assertType('Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem<Drupal\Core\Entity\EntityInterface>|null', $items->offsetGet(0));
+    foreach ($items as $item) {
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem<Drupal\Core\Entity\EntityInterface>', $item);
+    }
+    assertType('array<int, Drupal\Core\Entity\EntityInterface>', $items->referencedEntities());
+    foreach ($items->referencedEntities() as $entity) {
+        assertType('Drupal\Core\Entity\EntityInterface', $entity);
+    }
+}
+
+/**
+ * @param EntityReferenceFieldItemList<NodeInterface> $items
+ */
+function phpDocOverride(EntityReferenceFieldItemList $items): void {
+    assertType('Drupal\Core\Field\EntityReferenceFieldItemList<Drupal\node\NodeInterface>', $items);
+    assertType('Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem<Drupal\node\NodeInterface>|null', $items->first());
+    assertType('Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem<Drupal\node\NodeInterface>|null', $items->get(0));
+    assertType('Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem<Drupal\node\NodeInterface>|null', $items->offsetGet(0));
+    foreach ($items as $item) {
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem<Drupal\node\NodeInterface>', $item);
+    }
+    assertType('array<int, Drupal\node\NodeInterface>', $items->referencedEntities());
+    foreach ($items->referencedEntities() as $entity) {
+        assertType('Drupal\node\NodeInterface', $entity);
+    }
+}
+
+/**
+ * @extends EntityReferenceFieldItemList<NodeInterface>
+ */
+class ExtendedEntityReferenceFieldItemList extends EntityReferenceFieldItemList {}
+
+function extendedItemList(ExtendedEntityReferenceFieldItemList $items): void {
+    assertType('DrupalEntityReferenceFieldItemListGeneric\ExtendedEntityReferenceFieldItemList', $items);
+    assertType('Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem<Drupal\node\NodeInterface>|null', $items->first());
+    assertType('Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem<Drupal\node\NodeInterface>|null', $items->get(0));
+    assertType('Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem<Drupal\node\NodeInterface>|null', $items->offsetGet(0));
+    foreach ($items as $item) {
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem<Drupal\node\NodeInterface>', $item);
+        assertType('Drupal\node\NodeInterface|null', $item->entity);
+        assertType('int|string|null', $item->target_id);
+    }
+    assertType('array<int, Drupal\node\NodeInterface>', $items->referencedEntities());
+    foreach ($items->referencedEntities() as $entity) {
+        assertType('Drupal\node\NodeInterface', $entity);
+    }
+}
diff --git a/tests/src/Generics/data/entity-reference-formatter-base.php b/tests/src/Generics/data/entity-reference-formatter-base.php
new file mode 100644
index 00000000..6068e69f
--- /dev/null
+++ b/tests/src/Generics/data/entity-reference-formatter-base.php
@@ -0,0 +1,47 @@
+<?php
+
+namespace DrupalEntityReferenceFormatterBaseGeneric;
+
+use Drupal\Core\Field\FieldItemListInterface;
+use Drupal\Core\Field\Plugin\Field\FieldFormatter\EntityReferenceFormatterBase;
+use Drupal\node\NodeInterface;
+use function PHPStan\Testing\assertType;
+
+class InheritedEntityReferenceFormatterBase extends EntityReferenceFormatterBase {
+
+    public function prepareView(array $entities_items): void {
+        assertType('array<Drupal\Core\Field\EntityReferenceFieldItemList<Drupal\Core\Entity\EntityInterface>>', $entities_items);
+        $items = $entities_items[0];
+        assertType('Drupal\Core\Field\EntityReferenceFieldItemList<Drupal\Core\Entity\EntityInterface>', $items);
+    }
+
+    public function view(FieldItemListInterface $items, $langcode = NULL) {
+        assertType('Drupal\Core\Field\EntityReferenceFieldItemList<Drupal\Core\Entity\EntityInterface>', $items);
+    }
+
+    public function viewElements(FieldItemListInterface $items, $langcode) {
+        assertType('Drupal\Core\Field\EntityReferenceFieldItemList<Drupal\Core\Entity\EntityInterface>', $items);
+    }
+
+}
+
+/**
+ * @extends EntityReferenceFormatterBase<NodeInterface>
+ */
+class SpecifiedEntityTypeEntityReferenceFormatterBase extends EntityReferenceFormatterBase {
+
+    public function prepareView(array $entities_items): void {
+        assertType('array<Drupal\Core\Field\EntityReferenceFieldItemList<Drupal\node\NodeInterface>>', $entities_items);
+        $items = $entities_items[0];
+        assertType('Drupal\Core\Field\EntityReferenceFieldItemList<Drupal\node\NodeInterface>', $items);
+    }
+
+    public function view(FieldItemListInterface $items, $langcode = NULL) {
+        assertType('Drupal\Core\Field\EntityReferenceFieldItemList<Drupal\node\NodeInterface>', $items);
+    }
+
+    public function viewElements(FieldItemListInterface $items, $langcode) {
+        assertType('Drupal\Core\Field\EntityReferenceFieldItemList<Drupal\node\NodeInterface>', $items);
+    }
+
+}
diff --git a/tests/src/Generics/data/entity-reference-item.php b/tests/src/Generics/data/entity-reference-item.php
new file mode 100644
index 00000000..b3f49dff
--- /dev/null
+++ b/tests/src/Generics/data/entity-reference-item.php
@@ -0,0 +1,33 @@
+<?php
+
+namespace DrupalEntityReferenceItemGeneric;
+
+use Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem;
+use Drupal\node\NodeInterface;
+use function PHPStan\Testing\assertType;
+
+function defaultItem(EntityReferenceItem $item): void {
+    assertType('Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem', $item);
+    assertType('Drupal\Core\Entity\EntityInterface|null', $item->entity);
+    assertType('int|string|null', $item->target_id);
+}
+
+/**
+ * @param EntityReferenceItem<NodeInterface> $item
+ */
+function phpDocOverride(EntityReferenceItem $item): void {
+    assertType('Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem<Drupal\node\NodeInterface>', $item);
+    assertType('Drupal\node\NodeInterface|null', $item->entity);
+    assertType('int|string|null', $item->target_id);
+}
+
+/**
+ * @extends EntityReferenceItem<NodeInterface>
+ */
+class ExtendedEntityReferenceItem extends EntityReferenceItem {}
+
+function extendedItem(ExtendedEntityReferenceItem $item): void {
+    assertType('DrupalEntityReferenceItemGeneric\ExtendedEntityReferenceItem', $item);
+    assertType('Drupal\node\NodeInterface|null', $item->entity);
+    assertType('int|string|null', $item->target_id);
+}
diff --git a/tests/src/Generics/data/formatter-base.php b/tests/src/Generics/data/formatter-base.php
new file mode 100644
index 00000000..f1eb7102
--- /dev/null
+++ b/tests/src/Generics/data/formatter-base.php
@@ -0,0 +1,95 @@
+<?php
+
+namespace DrupalFormatterBaseGeneric;
+
+use Drupal\Core\Field\FieldItemList;
+use Drupal\Core\Field\FieldItemListInterface;
+use Drupal\Core\Field\FormatterBase;
+use Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem;
+use Drupal\Core\Field\Plugin\Field\FieldType\StringItem;
+use function PHPStan\Testing\assertType;
+
+/**
+ * Provides a custom field item list with concrete FieldItemListInterface<T>.
+ *
+ * @implements FieldItemListInterface<BooleanItem>
+ */
+class BooleanFieldItemList implements FieldItemListInterface {}
+
+/**
+ * @extends FormatterBase<BooleanFieldItemList>
+ */
+class ExtendsBooleanItemFormatter extends FormatterBase {
+
+    public function prepareView(array $entities_items): void {
+        assertType('array<DrupalFormatterBaseGeneric\BooleanFieldItemList>', $entities_items);
+        $items = $entities_items[0];
+        assertType('DrupalFormatterBaseGeneric\BooleanFieldItemList', $items);
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|null', $items->first());
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|null', $items->get(0));
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|null', $items->offsetGet(0));
+        foreach ($items as $item) {
+            assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem', $item);
+        }
+    }
+
+    public function view(FieldItemListInterface $items, $langcode = NULL) {
+        assertType('DrupalFormatterBaseGeneric\BooleanFieldItemList', $items);
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|null', $items->first());
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|null', $items->get(0));
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|null', $items->offsetGet(0));
+        foreach ($items as $item) {
+            assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem', $item);
+        }
+    }
+
+    public function viewElements(FieldItemListInterface $items, $langcode) {
+        assertType('DrupalFormatterBaseGeneric\BooleanFieldItemList', $items);
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|null', $items->first());
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|null', $items->get(0));
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|null', $items->offsetGet(0));
+        foreach ($items as $item) {
+            assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem', $item);
+        }
+    }
+
+}
+
+/**
+ * @extends FormatterBase<FieldItemList<StringItem>>
+ */
+class ExtendedDeepFormatter extends FormatterBase {
+
+    public function prepareView(array $entities_items): void {
+        assertType('array<Drupal\Core\Field\FieldItemList<Drupal\Core\Field\Plugin\Field\FieldType\StringItem>>', $entities_items);
+        $items = $entities_items[0];
+        assertType('Drupal\Core\Field\FieldItemList<Drupal\Core\Field\Plugin\Field\FieldType\StringItem>', $items);
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\StringItem|null', $items->first());
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\StringItem|null', $items->get(0));
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\StringItem|null', $items->offsetGet(0));
+        foreach ($items as $item) {
+            assertType('Drupal\Core\Field\Plugin\Field\FieldType\StringItem', $item);
+        }
+    }
+
+    public function view(FieldItemListInterface $items, $langcode = NULL) {
+        assertType('Drupal\Core\Field\FieldItemList<Drupal\Core\Field\Plugin\Field\FieldType\StringItem>', $items);
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\StringItem|null', $items->first());
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\StringItem|null', $items->get(0));
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\StringItem|null', $items->offsetGet(0));
+        foreach ($items as $item) {
+            assertType('Drupal\Core\Field\Plugin\Field\FieldType\StringItem', $item);
+        }
+    }
+
+    public function viewElements(FieldItemListInterface $items, $langcode) {
+        assertType('Drupal\Core\Field\FieldItemList<Drupal\Core\Field\Plugin\Field\FieldType\StringItem>', $items);
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\StringItem|null', $items->first());
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\StringItem|null', $items->get(0));
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\StringItem|null', $items->offsetGet(0));
+        foreach ($items as $item) {
+            assertType('Drupal\Core\Field\Plugin\Field\FieldType\StringItem', $item);
+        }
+    }
+
+}
diff --git a/tests/src/Generics/data/formatter-interface.php b/tests/src/Generics/data/formatter-interface.php
new file mode 100644
index 00000000..086c265b
--- /dev/null
+++ b/tests/src/Generics/data/formatter-interface.php
@@ -0,0 +1,220 @@
+<?php
+
+namespace DrupalFormatterInterfaceGeneric;
+
+use Drupal\Core\Field\FieldItemList;
+use Drupal\Core\Field\FieldItemListInterface;
+use Drupal\Core\Field\FormatterInterface;
+use Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem;
+use Drupal\Core\Field\Plugin\Field\FieldType\StringItem;
+use function PHPStan\Testing\assertType;
+
+/**
+ * Tests the class which doesn't use generics at all.
+ */
+class EmptyFormatter implements FormatterInterface {
+
+    public function prepareView(array $entities_items): void {
+        assertType('array<Drupal\Core\Field\FieldItemListInterface>', $entities_items);
+        $items = $entities_items[0];
+        assertType('Drupal\Core\Field\FieldItemListInterface', $items);
+        assertType('Drupal\Core\TypedData\TypedDataInterface|null', $items->first());
+        assertType('Drupal\Core\TypedData\TypedDataInterface|null', $items->get(0));
+        assertType('Drupal\Core\TypedData\TypedDataInterface|null', $items->offsetGet(0));
+        foreach ($items as $item) {
+            assertType('mixed', $item);
+        }
+    }
+
+    public function view(FieldItemListInterface $items, $langcode = NULL) {
+        assertType('Drupal\Core\Field\FieldItemListInterface', $items);
+        assertType('Drupal\Core\TypedData\TypedDataInterface|null', $items->first());
+        assertType('Drupal\Core\TypedData\TypedDataInterface|null', $items->get(0));
+        assertType('Drupal\Core\TypedData\TypedDataInterface|null', $items->offsetGet(0));
+        foreach ($items as $item) {
+            assertType('mixed', $item);
+        }
+    }
+
+    public function viewElements(FieldItemListInterface $items, $langcode) {
+        assertType('Drupal\Core\Field\FieldItemListInterface', $items);
+        assertType('Drupal\Core\TypedData\TypedDataInterface|null', $items->first());
+        assertType('Drupal\Core\TypedData\TypedDataInterface|null', $items->get(0));
+        assertType('Drupal\Core\TypedData\TypedDataInterface|null', $items->offsetGet(0));
+        foreach ($items as $item) {
+            assertType('mixed', $item);
+        }
+    }
+
+}
+
+/**
+ * Tests the class which provides TFieldItemList data to generic.
+ *
+ * @implements FormatterInterface<FieldItemList>
+ */
+class FieldItemListFormatter implements FormatterInterface {
+
+    public function prepareView(array $entities_items): void {
+        assertType('array<Drupal\Core\Field\FieldItemList>', $entities_items);
+        $items = $entities_items[0];
+        assertType('Drupal\Core\Field\FieldItemList', $items);
+        assertType('Drupal\Core\Field\FieldItemInterface|null', $items->first());
+        assertType('Drupal\Core\Field\FieldItemInterface|null', $items->get(0));
+        assertType('Drupal\Core\Field\FieldItemInterface|null', $items->offsetGet(0));
+        foreach ($items as $item) {
+            assertType('Drupal\Core\Field\FieldItemInterface', $item);
+        }
+    }
+
+    public function view(FieldItemListInterface $items, $langcode = NULL) {
+        assertType('Drupal\Core\Field\FieldItemList', $items);
+        assertType('Drupal\Core\Field\FieldItemInterface|null', $items->first());
+        assertType('Drupal\Core\Field\FieldItemInterface|null', $items->get(0));
+        assertType('Drupal\Core\Field\FieldItemInterface|null', $items->offsetGet(0));
+        foreach ($items as $item) {
+            assertType('Drupal\Core\Field\FieldItemInterface', $item);
+        }
+    }
+
+    public function viewElements(FieldItemListInterface $items, $langcode) {
+        assertType('Drupal\Core\Field\FieldItemList', $items);
+        assertType('Drupal\Core\Field\FieldItemInterface|null', $items->first());
+        assertType('Drupal\Core\Field\FieldItemInterface|null', $items->get(0));
+        assertType('Drupal\Core\Field\FieldItemInterface|null', $items->offsetGet(0));
+        foreach ($items as $item) {
+            assertType('Drupal\Core\Field\FieldItemInterface', $item);
+        }
+    }
+
+}
+
+/**
+ * Tests hierarchical generics.
+ *
+ * Provides TFieldItemList data to generic with specifying FieldItemList<T>.
+ *
+ * @implements FormatterInterface<FieldItemList<StringItem>>
+ */
+class StringItemFormatter implements FormatterInterface {
+
+    public function prepareView(array $entities_items): void {
+        assertType('array<Drupal\Core\Field\FieldItemList<Drupal\Core\Field\Plugin\Field\FieldType\StringItem>>', $entities_items);
+        $items = $entities_items[0];
+        assertType('Drupal\Core\Field\FieldItemList<Drupal\Core\Field\Plugin\Field\FieldType\StringItem>', $items);
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\StringItem|null', $items->first());
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\StringItem|null', $items->get(0));
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\StringItem|null', $items->offsetGet(0));
+        foreach ($items as $item) {
+            assertType('Drupal\Core\Field\Plugin\Field\FieldType\StringItem', $item);
+        }
+    }
+
+    public function view(FieldItemListInterface $items, $langcode = NULL) {
+        assertType('Drupal\Core\Field\FieldItemList<Drupal\Core\Field\Plugin\Field\FieldType\StringItem>', $items);
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\StringItem|null', $items->first());
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\StringItem|null', $items->get(0));
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\StringItem|null', $items->offsetGet(0));
+        foreach ($items as $item) {
+            assertType('Drupal\Core\Field\Plugin\Field\FieldType\StringItem', $item);
+        }
+    }
+
+    public function viewElements(FieldItemListInterface $items, $langcode) {
+        assertType('Drupal\Core\Field\FieldItemList<Drupal\Core\Field\Plugin\Field\FieldType\StringItem>', $items);
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\StringItem|null', $items->first());
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\StringItem|null', $items->get(0));
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\StringItem|null', $items->offsetGet(0));
+        foreach ($items as $item) {
+            assertType('Drupal\Core\Field\Plugin\Field\FieldType\StringItem', $item);
+        }
+    }
+
+}
+
+/**
+ * Tests providing union types with hierarchical generics.
+ *
+ * @implements FormatterInterface<FieldItemList<StringItem|BooleanItem>>
+ */
+class UnionTypeFormatter implements FormatterInterface {
+
+    public function prepareView(array $entities_items): void {
+        assertType('array<Drupal\Core\Field\FieldItemList<Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|Drupal\Core\Field\Plugin\Field\FieldType\StringItem>>', $entities_items);
+        $items = $entities_items[0];
+        assertType('Drupal\Core\Field\FieldItemList<Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|Drupal\Core\Field\Plugin\Field\FieldType\StringItem>', $items);
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|Drupal\Core\Field\Plugin\Field\FieldType\StringItem|null', $items->first());
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|Drupal\Core\Field\Plugin\Field\FieldType\StringItem|null', $items->get(0));
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|Drupal\Core\Field\Plugin\Field\FieldType\StringItem|null', $items->offsetGet(0));
+        foreach ($items as $item) {
+            assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|Drupal\Core\Field\Plugin\Field\FieldType\StringItem', $item);
+        }
+    }
+
+    public function view(FieldItemListInterface $items, $langcode = NULL) {
+        assertType('Drupal\Core\Field\FieldItemList<Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|Drupal\Core\Field\Plugin\Field\FieldType\StringItem>', $items);
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|Drupal\Core\Field\Plugin\Field\FieldType\StringItem|null', $items->first());
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|Drupal\Core\Field\Plugin\Field\FieldType\StringItem|null', $items->get(0));
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|Drupal\Core\Field\Plugin\Field\FieldType\StringItem|null', $items->offsetGet(0));
+        foreach ($items as $item) {
+            assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|Drupal\Core\Field\Plugin\Field\FieldType\StringItem', $item);
+        }
+    }
+
+    public function viewElements(FieldItemListInterface $items, $langcode) {
+        assertType('Drupal\Core\Field\FieldItemList<Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|Drupal\Core\Field\Plugin\Field\FieldType\StringItem>', $items);
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|Drupal\Core\Field\Plugin\Field\FieldType\StringItem|null', $items->first());
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|Drupal\Core\Field\Plugin\Field\FieldType\StringItem|null', $items->get(0));
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|Drupal\Core\Field\Plugin\Field\FieldType\StringItem|null', $items->offsetGet(0));
+        foreach ($items as $item) {
+            assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|Drupal\Core\Field\Plugin\Field\FieldType\StringItem', $item);
+        }
+    }
+
+}
+
+/**
+ * Provides a custom field item list with concrete FieldItemListInterface<T>.
+ *
+ * @implements FieldItemListInterface<BooleanItem>
+ */
+class BooleanFieldItemList implements FieldItemListInterface {}
+
+/**
+ * @implements FormatterInterface<BooleanFieldItemList>
+ */
+class BooleanItemFormatter implements FormatterInterface {
+
+    public function prepareView(array $entities_items): void {
+        assertType('array<DrupalFormatterInterfaceGeneric\BooleanFieldItemList>', $entities_items);
+        $items = $entities_items[0];
+        assertType('DrupalFormatterInterfaceGeneric\BooleanFieldItemList', $items);
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|null', $items->first());
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|null', $items->get(0));
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|null', $items->offsetGet(0));
+        foreach ($items as $item) {
+            assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem', $item);
+        }
+    }
+
+    public function view(FieldItemListInterface $items, $langcode = NULL) {
+        assertType('DrupalFormatterInterfaceGeneric\BooleanFieldItemList', $items);
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|null', $items->first());
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|null', $items->get(0));
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|null', $items->offsetGet(0));
+        foreach ($items as $item) {
+            assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem', $item);
+        }
+    }
+
+    public function viewElements(FieldItemListInterface $items, $langcode) {
+        assertType('DrupalFormatterInterfaceGeneric\BooleanFieldItemList', $items);
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|null', $items->first());
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|null', $items->get(0));
+        assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem|null', $items->offsetGet(0));
+        foreach ($items as $item) {
+            assertType('Drupal\Core\Field\Plugin\Field\FieldType\BooleanItem', $item);
+        }
+    }
+
+}