Readonly properties cannot be unset()

Author: staabm

src/Rules/Variables/UnsetRule.php

@@ -69,6 +69,45 @@ private function canBeUnset(Node $node, Scope $scope): ?IdentifierRuleError
 			}
 
 			return $this->canBeUnset($node->var, $scope);
+		} elseif (
+			$node instanceof Node\Expr\PropertyFetch
+			&& $node->name instanceof Node\Identifier
+		) {
+			$type = $scope->getType($node->var);
+			foreach ($type->getObjectClassReflections() as $classReflection) {
+				if ($classReflection->isReadOnly() || $classReflection->isImmutable()) {
+					return RuleErrorBuilder::message(
+						sprintf(
+							'Cannot unset property %s of %s class %s.',
+							$node->name->name,
+							$classReflection->isReadOnly() ? 'readonly' : 'immutable',
+							$type->describe(VerbosityLevel::value()),
+						),
+					)
+						->line($node->getStartLine())
+						->identifier('unset.readonlyClass')
+						->build();
+				}
+
+				if (!$classReflection->hasProperty($node->name->name)) {
+					continue;
+				}
+
+				$propertyReflection = $classReflection->getNativeProperty($node->name->name);
+				if ($propertyReflection->isReadOnly() || $propertyReflection->isReadOnlyByPhpDoc()) {
+					return RuleErrorBuilder::message(
+						sprintf(
+							'Cannot unset %s property %s of %s.',
+							$propertyReflection->isReadOnly() ? 'readonly' : '@readonly',
+							$node->name->name,
+							$type->describe(VerbosityLevel::value()),
+						),
+					)
+						->line($node->getStartLine())
+						->identifier('unset.readonlyProperty')
+						->build();
+				}
+			}
 		}
 
 		return null;

tests/PHPStan/Rules/Variables/UnsetRuleTest.php

@@ -91,4 +91,30 @@ public function testBug4565(): void
 		$this->analyse([__DIR__ . '/../../Analyser/nsrt/bug-4565.php'], []);
 	}
 
+	public function testBug12421(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-12421.php'], [
+			[
+				'Cannot unset property y of readonly class Bug12421\NativeReadonlyClass.',
+				78,
+			],
+			[
+				'Cannot unset readonly property y of Bug12421\NativeReadonlyProperty.',
+				82,
+			],
+			[
+				'Cannot unset property y of immutable class Bug12421\PhpdocReadonlyClass.',
+				86,
+			],
+			[
+				'Cannot unset @readonly property y of Bug12421\PhpdocReadonlyProperty.',
+				90,
+			],
+			[
+				'Cannot unset property y of immutable class Bug12421\PhpdocImmutableClass.',
+				94,
+			],
+		]);
+	}
+
 }

tests/PHPStan/Rules/Variables/data/bug-12421.php

@@ -0,0 +1,97 @@
+<?php // lint >= 8.2
+
+namespace Bug12421;
+
+readonly class NativeReadonlyClass
+{
+	public Y $y;
+
+	public function __construct()
+	{
+		$this->y = new Y();
+	}
+}
+
+class NativeReadonlyProperty
+{
+	public readonly Y $y;
+
+	public function __construct()
+	{
+		$this->y = new Y();
+	}
+}
+
+/** @readonly */
+class PhpdocReadonlyClass
+{
+	public Y $y;
+
+	public function __construct()
+	{
+		$this->y = new Y();
+	}
+}
+
+class PhpdocReadonlyProperty
+{
+	/** @readonly */
+	public Y $y;
+
+	public function __construct()
+	{
+		$this->y = new Y();
+	}
+}
+
+/** @immutable  */
+class PhpdocImmutableClass
+{
+	public Y $y;
+
+	public function __construct()
+	{
+		$this->y = new Y();
+	}
+}
+
+class RegularProperty
+{
+	public Y $y;
+
+	public function __construct()
+	{
+		$this->y = new Y();
+	}
+}
+
+class Y
+{
+}
+
+function doFoo() {
+	$x = new RegularProperty();
+	unset($x->y);
+	var_dump($x->y);
+
+	$x = new NativeReadonlyClass();
+	unset($x->y);
+	var_dump($x->y);
+
+	$x = new NativeReadonlyProperty();
+	unset($x->y);
+	var_dump($x->y);
+
+	$x = new PhpdocReadonlyClass();
+	unset($x->y);
+	var_dump($x->y);
+
+	$x = new PhpdocReadonlyProperty();
+	unset($x->y);
+	var_dump($x->y);
+
+	$x = new PhpdocImmutableClass();
+	unset($x->y);
+	var_dump($x->y);
+}
+