Regression test

Closes phpstan/phpstan#6861
Closes phpstan/phpstan#5629

Author: ondrejmirtes

tests/PHPStan/Analyser/UnknownMixedTypeOnOlderPhpTest.php

@@ -0,0 +1,42 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Analyser;
+
+use PHPStan\Rules\Methods\ExistingClassesInTypehintsRule;
+use PHPStan\Rules\Rule as TRule;
+use PHPStan\Testing\RuleTestCase;
+use function array_merge;
+
+/**
+ * @extends RuleTestCase<ExistingClassesInTypehintsRule>
+ */
+class UnknownMixedTypeOnOlderPhpTest extends RuleTestCase
+{
+
+	protected function getRule(): TRule
+	{
+		return self::getContainer()->getByType(ExistingClassesInTypehintsRule::class);
+	}
+
+	public function testMixedUnknownType(): void
+	{
+		$this->analyse([__DIR__ . '/data/unknown-mixed-type.php'], [
+			[
+				'Parameter $m of method UnknownMixedType\Foo::doFoo() has invalid type UnknownMixedType\mixed.',
+				8,
+			],
+			[
+				'Method UnknownMixedType\Foo::doFoo() has invalid return type UnknownMixedType\mixed.',
+				8,
+			],
+		]);
+	}
+
+	public static function getAdditionalConfigFiles(): array
+	{
+		return array_merge(parent::getAdditionalConfigFiles(), [
+			__DIR__ . '/unknown-mixed-type.neon',
+		]);
+	}
+
+}

tests/PHPStan/Analyser/data/unknown-mixed-type.php

@@ -0,0 +1,13 @@
+<?php
+
+namespace UnknownMixedType;
+
+class Foo
+{
+
+	public function doFoo(mixed $m): mixed
+	{
+
+	}
+
+}

tests/PHPStan/Analyser/unknown-mixed-type.neon

@@ -0,0 +1,2 @@
+parameters:
+	phpVersion: 70400