is_a(): add some more type-specifier tests

Author: jiripudil

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -9981,6 +9981,11 @@ public function dataIsNumeric(): array
 		return $this->gatherAssertTypes(__DIR__ . '/data/is-numeric.php');
 	}
 
+	public function dataIsA(): array
+	{
+		return $this->gatherAssertTypes(__DIR__ . '/data/is-a.php');
+	}
+
 	public function dataBug3142(): array
 	{
 		return $this->gatherAssertTypes(__DIR__ . '/data/bug-3142.php');
@@ -10537,6 +10542,7 @@ private function gatherAssertTypes(string $file): array
 	 * @dataProvider dataExtDs
 	 * @dataProvider dataArrowFunctionReturnTypeInference
 	 * @dataProvider dataIsNumeric
+	 * @dataProvider dataIsA
 	 * @dataProvider dataBug3142
 	 * @dataProvider dataArrayShapeKeysStrings
 	 * @dataProvider dataBug1216

tests/PHPStan/Analyser/data/is-a.php

@@ -0,0 +1,28 @@
+<?php
+
+function (object $foo) {
+	if (is_a($foo, Foo::class)) {
+		\PHPStan\Analyser\assertType('Foo', $foo);
+	}
+};
+
+function (object $foo) {
+	/** @var class-string<Foo> $fooClassString */
+	$fooClassString = 'Foo';
+
+	if (is_a($foo, $fooClassString)) {
+		\PHPStan\Analyser\assertType('Foo', $foo);
+	}
+};
+
+function (string $foo) {
+	if (is_a($foo, Foo::class, true)) {
+		\PHPStan\Analyser\assertType('class-string<Foo>', $foo);
+	}
+};
+
+function (string $foo, string $someString) {
+	if (is_a($foo, $someString, true)) {
+		\PHPStan\Analyser\assertType('class-string<object>', $foo);
+	}
+};