Prevent declaring hooked properties as readonly

Author: jakubtobiasz

Makefile

@@ -88,6 +88,7 @@ lint:
 		--exclude tests/PHPStan/Rules/Properties/data/non-abstract-hooked-properties-in-class.php \
 		--exclude tests/PHPStan/Rules/Properties/data/hooked-properties-in-class.php \
 		--exclude tests/PHPStan/Rules/Properties/data/hooked-properties-without-bodies-in-class.php \
+		--exclude tests/PHPStan/Rules/Properties/data/readonly-property-hooks.php \
 		--exclude tests/PHPStan/Rules/Classes/data/bug-12281.php \
 		--exclude tests/PHPStan/Rules/Traits/data/bug-12281.php \
 		--exclude tests/PHPStan/Rules/Classes/data/invalid-hooked-properties.php \

src/Rules/Properties/PropertyInClassRule.php

@@ -76,6 +76,17 @@ public function processNode(Node $node, Scope $scope): array
 			return [];
 		}
 
+		if ($node->isReadOnly()) {
+			if ($node->hasHooks()) {
+				return [
+					RuleErrorBuilder::message('Hooked properties cannot be readonly.')
+						->nonIgnorable()
+						->identifier('property.hookReadOnly')
+						->build(),
+				];
+			}
+		}
+
 		if (!$this->doAllHooksHaveBody($node)) {
 			return [
 				RuleErrorBuilder::message('Non-abstract properties cannot include hooks without bodies.')

tests/PHPStan/Rules/Properties/PropertyInClassRuleTest.php

@@ -151,4 +151,26 @@ public function testPhp84AndAbstractHookedPropertiesWithBodies(): void
 		]);
 	}
 
+	public function testPhp84AndReadonlyHookedProperties(): void
+	{
+		if (PHP_VERSION_ID < 80400) {
+			$this->markTestSkipped('Test requires PHP 8.4 or later.');
+		}
+
+		$this->analyse([__DIR__ . '/data/readonly-property-hooks.php'], [
+			[
+				'Hooked properties cannot be readonly.',
+				7,
+			],
+			[
+				'Hooked properties cannot be readonly.',
+				12,
+			],
+			[
+				'Hooked properties cannot be readonly.',
+				14,
+			],
+		]);
+	}
+
 }

tests/PHPStan/Rules/Properties/data/readonly-property-hooks.php

@@ -0,0 +1,15 @@
+<?php declare(strict_types=1);
+
+namespace ReadonlyPropertyHooks;
+
+class HelloWorld
+{
+	public readonly string $firstName {
+		get => $this->firstName;
+		set => $this->firstName;
+	}
+
+	public readonly string $middleName { get => $this->middleName; }
+
+	public readonly string $lastName { set => $this->lastName; }
+}