Regression test

Author: ondrejmirtes

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -10339,6 +10339,7 @@ public function dataFileAsserts(): iterable
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-4700.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/phpdoc-in-closure-bind.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/multi-assign.php');
+		yield from $this->gatherAssertTypes(__DIR__ . '/data/generics-reduce-types-first.php');
 	}
 
 	/**

tests/PHPStan/Analyser/data/generics-reduce-types-first.php

@@ -0,0 +1,35 @@
+<?php
+
+// inspired by: https://github.com/microsoft/TypeScript/pull/5738
+
+namespace GenericsReduceTypesFirst;
+
+use function PHPStan\Analyser\assertType;
+
+class Foo
+{
+
+	/**
+	 * @template T
+	 * @param T|string $p
+	 * @return T
+	 */
+	public function doFoo($p)
+	{
+
+	}
+
+	/**
+	 * @param string[]|string $a
+	 * @param string|string[] $b
+	 * @param string[] $c
+	 */
+	public function doBar($a, $b, $c, string $d)
+	{
+		assertType('array<string>', $this->doFoo($a));
+		assertType('array<string>', $this->doFoo($b));
+		assertType('array<string>', $this->doFoo($c));
+		assertType('string', $this->doFoo($d));
+	}
+
+}