Fix php-ds/ext-ds#44

Author: simPod

src/Sequence.php

@@ -70,11 +70,11 @@ function contains(...$values): bool;
     function filter(callable $callback = null): Sequence;
 
     /**
-     * Returns the index of a given value, or false if it could not be found.
+     * Returns the index of a given value, or null if it could not be found.
      *
      * @param mixed $value
      *
-     * @return int|false
+     * @return int|null
      *
      * @psalm-param TValue $value
      */

src/Traits/GenericSequence.php

@@ -80,7 +80,7 @@ public function count(): int
     public function contains(...$values): bool
     {
         foreach ($values as $value) {
-            if ($this->find($value) === false) {
+            if ($this->find($value) === null) {
                 return false;
             }
         }
@@ -101,7 +101,9 @@ public function filter(callable $callback = null): Sequence
      */
     public function find($value)
     {
-        return array_search($value, $this->array, true);
+        $offset = array_search($value, $this->array, true);
+
+        return $offset === false ? null : $offset;
     }
 
     /**