Add FilterIterator stub

Author: jdecool

conf/config.neon

@@ -24,6 +24,7 @@ parameters:
 disableRuntimeReflectionProvider: false
 skipCheckGenericClasses:
 - DatePeriod
+- FilterIterator
 fileExtensions:
 - php
 checkAdvancedIsset: false

stubs/iterable.stub

@@ -193,6 +193,18 @@ class IteratorIterator implements OuterIterator {
  public function __construct(Traversable $iterator) {}
 }
 
+/**
+ * @template-covariant TKey
+ * @template-covariant TValue
+ * @template TIterator as Traversable<TKey, TValue>
+ *
+ * @template-extends IteratorIterator<TKey, TValue, TIterator>
+ */
+class FilterIterator extends IteratorIterator
+{
+
+}
+
 /**
  * @template TKey of array-key
  * @template TValue