Regression test

Closes phpstan/phpstan#2723

Author: ondrejmirtes

tests/PHPStan/Rules/Functions/ReturnTypeRuleTest.php

@@ -89,4 +89,15 @@ public function testBug2568(): void
 		$this->analyse([__DIR__ . '/data/bug-2568.php'], []);
 	}
 
+	public function testBug2723(): void
+	{
+		require_once __DIR__ . '/data/bug-2723.php';
+		$this->analyse([__DIR__ . '/data/bug-2723.php'], [
+			[
+				'Function Bug2723\baz() should return Bug2723\Bar<Bug2723\Foo<T4>> but returns Bug2723\BarOfFoo<string>.',
+				55,
+			],
+		]);
+	}
+
 }

tests/PHPStan/Rules/Functions/data/bug-2723.php

@@ -0,0 +1,66 @@
+<?php declare(strict_types=1);
+
+namespace Bug2723;
+
+/**
+ * @template T1
+ */
+class Foo
+{
+	/** @var T1 */
+	public $t;
+
+	/** @param T1 $t */
+	public function __construct($t)
+	{
+		$this->t = $t;
+	}
+}
+
+/**
+ * @template T2
+ */
+class Bar
+{
+	/** @var T2 */
+	public $t;
+
+	/** @param T2 $t */
+	public function __construct($t)
+	{
+		$this->t = $t;
+	}
+}
+
+/**
+ * @template T3
+ * @extends Bar<Foo<T3>>
+ */
+class BarOfFoo extends Bar
+{
+	/** @param T3 $t */
+	public function __construct($t)
+	{
+		parent::__construct(new Foo($t));
+	}
+}
+
+/**
+ * @template T4
+ * @param T4 $t
+ * @return Bar<Foo<T4>>
+ */
+function baz($t)
+{
+	return new BarOfFoo("hello");
+}
+
+/**
+ * @template T4
+ * @param T4 $t
+ * @return Bar<Foo<T4>>
+ */
+function baz2($t)
+{
+	return new BarOfFoo($t);
+}