Add test

Author: VincentLanglet

tests/PHPStan/Analyser/nsrt/bug-9456.php

@@ -0,0 +1,71 @@
+<?php declare(strict_types = 1);
+
+namespace Bug9456;
+
+use ArrayAccess;
+
+use function PHPStan\Testing\assertType;
+
+/**
+ * @template TKey of array-key
+ * @template TValue of mixed
+ *
+ * @implements ArrayAccess<TKey, TValue>
+ */
+class Collection implements ArrayAccess {
+	/**
+	 * @param (callable(TValue, TKey): bool)|TValue|string $key
+	 * @param TValue|string|null $operator
+	 * @param TValue|null $value
+	 * @return static<int<0, 1>, static<TKey, TValue>>
+	 */
+	public function partition($key, $operator = null, $value = null) {} // @phpstan-ignore-line
+
+	/**
+	 * @param TKey $key
+	 * @return TValue
+	 */
+	public function offsetGet($key): mixed { return null; } // @phpstan-ignore-line
+
+	/**
+	 * @param TKey $key
+	 * @return bool
+	 */
+	public function offsetExists($key): bool { return true; }
+
+	/**
+	 * @param TKey|null $key
+	 * @param TValue $value
+	 * @return void
+	 */
+	public function offsetSet($key, $value): void {}
+
+	/**
+	 * @param TKey $key
+	 * @return void
+	 */
+	public function offsetUnset($key): void {}
+}
+
+class HelloWorld
+{
+	/**
+	 * @param Collection<int, string> $collection
+	 */
+	public function sayHello(Collection $collection): void
+	{
+		$result = $collection->partition('key');
+
+		assertType(
+			'Collection<int<0, 1>, Collection<int, string>>',
+			$result
+		);
+		assertType('Collection<int, string>', $result[0]);
+		assertType('Collection<int, string>', $result[1]);
+
+		[$one, $two] = $collection->partition('key');
+
+		assertType('Collection<int, string>', $one);
+		assertType('Collection<int, string>', $two);
+	}
+}