Add compatibility rule

Author: rvanvelzen

conf/config.level2.neon

@@ -35,6 +35,7 @@ rules:
 	- PHPStan\Rules\PhpDoc\MethodConditionalReturnTypeRule
 	- PHPStan\Rules\PhpDoc\FunctionAssertRule
 	- PHPStan\Rules\PhpDoc\MethodAssertRule
+	- PHPStan\Rules\PhpDoc\IncompatibleSelfOutTypeRule
 	- PHPStan\Rules\PhpDoc\IncompatibleClassConstantPhpDocTypeRule
 	- PHPStan\Rules\PhpDoc\IncompatiblePhpDocTypeRule
 	- PHPStan\Rules\PhpDoc\IncompatiblePropertyPhpDocTypeRule

src/Rules/PhpDoc/IncompatibleSelfOutTypeRule.php

@@ -0,0 +1,53 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\PhpDoc;
+
+use PhpParser\Node;
+use PHPStan\Analyser\Scope;
+use PHPStan\Node\InClassMethodNode;
+use PHPStan\Rules\Rule;
+use PHPStan\Rules\RuleErrorBuilder;
+use PHPStan\ShouldNotHappenException;
+use PHPStan\Type\ObjectType;
+use PHPStan\Type\VerbosityLevel;
+
+/**
+ * @implements Rule<InClassMethodNode>
+ */
+class IncompatibleSelfOutTypeRule implements Rule
+{
+
+	public function getNodeType(): string
+	{
+		return InClassMethodNode::class;
+	}
+
+	public function processNode(Node $node, Scope $scope): array
+	{
+		$method = $scope->getFunction();
+		if ($method === null) {
+			throw new ShouldNotHappenException();
+		}
+
+		$selfOutType = $method->getSelfOutType();
+		if ($selfOutType === null) {
+			return [];
+		}
+
+		$classReflection = $method->getDeclaringClass();
+		$classType = new ObjectType($classReflection->getName(), null, $classReflection);
+
+		if (!$classType->isSuperTypeOf($selfOutType)->no()) {
+			return [];
+		}
+
+		return [
+			RuleErrorBuilder::message(sprintf(
+				'Out type %s is not compatible with %s.',
+				$selfOutType->describe(VerbosityLevel::precise()),
+				$classType->describe(VerbosityLevel::precise()),
+			))->build(),
+		];
+	}
+
+}

tests/PHPStan/Rules/PhpDoc/IncompatibleSelfOutTypeRuleTest.php

@@ -0,0 +1,29 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\PhpDoc;
+
+use PHPStan\Rules\Rule;
+use PHPStan\Testing\RuleTestCase;
+
+/**
+ * @extends RuleTestCase<IncompatibleSelfOutTypeRule>
+ */
+class IncompatibleSelfOutTypeRuleTest extends RuleTestCase
+{
+
+	protected function getRule(): Rule
+	{
+		return new IncompatibleSelfOutTypeRule();
+	}
+
+	public function testRule(): void
+	{
+		$this->analyse([__DIR__ . '/data/incompatible-self-out-type.php'], [
+			[
+				'Out type int is not compatible with IncompatibleSelfOutType\A.',
+				23,
+			],
+		]);
+	}
+
+}

tests/PHPStan/Rules/PhpDoc/data/incompatible-self-out-type.php

@@ -0,0 +1,24 @@
+<?php
+
+namespace IncompatibleSelfOutType;
+
+/**
+ * @template T
+ */
+interface A
+{
+	/** @phpstan-self-out self */
+	public function one();
+
+	/**
+	 * @template NewT
+	 * @param NewT $param
+	 * @phpstan-self-out self<NewT>
+	 */
+	public function two($param);
+
+	/**
+	 * @phpstan-self-out int
+	 */
+	public function three();
+}