Implement require-extends rules

src/Rules/PhpDoc/RequireExtendsCheck.php

@@ -11,6 +11,7 @@
 use PHPStan\Type\ObjectType;
 use PHPStan\Type\VerbosityLevel;
 use function array_merge;
+use function count;
 use function sprintf;
 
 final class RequireExtendsCheck
@@ -30,6 +31,11 @@ public function __construct(
 	public function checkExtendsTags(Node $node, array $extendsTags): array
 	{
 		$errors = [];
+
+		if (count($extendsTags) > 1) {
+			$errors[] = RuleErrorBuilder::message(sprintf('PHPDoc tag @phpstan-require-extends can only be used once.'))->build();
+		}
+
 		foreach ($extendsTags as $extendsTag) {
 			$type = $extendsTag->getType();
 			if (!$type instanceof ObjectType) {

tests/PHPStan/Rules/PhpDoc/RequireExtendsDefinitionClassRuleTest.php

@@ -73,6 +73,10 @@ public function testRule(): void
 				'PHPDoc tag @phpstan-require-extends contains non-object type IncompatibleRequireExtends\UnresolvableExtendsInterface&stdClass.',
 				135,
 			],
+			[
+				'PHPDoc tag @phpstan-require-extends can only be used once.',
+				178,
+			],
 		]);
 	}
 

tests/PHPStan/Rules/PhpDoc/RequireExtendsDefinitionTraitRuleTest.php

@@ -36,6 +36,10 @@ public function testRule(): void
 				'PHPDoc tag @phpstan-require-extends contains non-object type *NEVER*.',
 				140,
 			],
+			[
+				'PHPDoc tag @phpstan-require-extends can only be used once.',
+				171,
+			],
 		]);
 	}
 

tests/PHPStan/Rules/PhpDoc/data/incompatible-require-extends.php

@@ -163,3 +163,16 @@ trait ValidPsalmTrait {}
 new class {
 	use ValidPsalmTrait;
 };
+
+/**
+ * @phpstan-require-extends SomeClass
+ * @phpstan-require-extends SomeOtherClass
+ */
+trait TooMuchExtends {}
+
+/**
+ * @phpstan-require-extends SomeClass
+ * @phpstan-require-extends SomeOtherClass
+ * @phpstan-require-extends SomeOtherClass
+ */
+interface TooMuchExtendsIface {}