Add stringable access check to AccessPropertiesCheck

src/Rules/Properties/AccessPropertiesCheck.php

@@ -40,6 +40,8 @@ public function __construct(
 		private bool $reportMagicProperties,
 		#[AutowiredParameter]
 		private bool $checkDynamicProperties,
+		#[AutowiredParameter(ref: '%featureToggles.checkNonStringableDynamicAccess%')]
+		private bool $checkNonStringableDynamicAccess,
 	)
 	{
 	}
@@ -49,13 +51,30 @@ public function __construct(
 	 */
 	public function check(PropertyFetch $node, Scope $scope, bool $write): array
 	{
+		$errors = [];
 		if ($node->name instanceof Identifier) {
 			$names = [$node->name->name];
 		} else {
 			$names = array_map(static fn (ConstantStringType $type): string => $type->getValue(), $scope->getType($node->name)->getConstantStrings());
+
+			if (!$write && $this->checkNonStringableDynamicAccess) {
+				$nameTypeResult = $this->ruleLevelHelper->findTypeToCheck(
+					$scope,
+					$node->name,
+					'',
+					static fn (Type $type) => $type->toString()->isString()->yes(),
+				);
+				$nameType = $nameTypeResult->getType();
+				if ($nameType instanceof ErrorType || $nameType->toString() instanceof ErrorType || !$nameType->toString()->isString()->yes()) {
+					$originalNameType = $scope->getType($node->name);
+					$className = $scope->getType($node->var)->describe(VerbosityLevel::typeOnly());
+					$errors[] = RuleErrorBuilder::message(sprintf('Property name for %s must be a string, but %s was given.', $className, $originalNameType->describe(VerbosityLevel::precise())))
+						->identifier('property.nameNotString')
+						->build();
+				}
+			}
 		}
 
-		$errors = [];
 		foreach ($names as $name) {
 			$errors = array_merge($errors, $this->processSingleProperty($scope, $node, $name, $write));
 		}

tests/PHPStan/Rules/Properties/AccessPropertiesInAssignRuleTest.php

@@ -19,7 +19,7 @@ protected function getRule(): Rule
 	{
 		$reflectionProvider = self::createReflectionProvider();
 		return new AccessPropertiesInAssignRule(
-			new AccessPropertiesCheck($reflectionProvider, new RuleLevelHelper($reflectionProvider, true, false, true, false, false, false, true), new PhpVersion(PHP_VERSION_ID), true, true),
+			new AccessPropertiesCheck($reflectionProvider, new RuleLevelHelper($reflectionProvider, true, false, true, false, false, false, true), new PhpVersion(PHP_VERSION_ID), true, true, true),
 		);
 	}
 
@@ -96,6 +96,21 @@ public function testBug4492(): void
 		$this->analyse([__DIR__ . '/data/bug-4492.php'], []);
 	}
 
+	public function testDynamicStringableAccess(): void
+	{
+		// All warnings are reported by the AccessPropertiesRule.
+		// The AccessPropertiesInAssignRule does not report any warnings.
+		$this->analyse([__DIR__ . '/data/dynamic-stringable-access.php'], []);
+	}
+
+	#[RequiresPhp('>= 8.0')]
+	public function testDynamicStringableNullsafeAccess(): void
+	{
+		// All warnings are reported by the AccessPropertiesRule.
+		// The AccessPropertiesInAssignRule does not report any warnings.
+		$this->analyse([__DIR__ . '/data/dynamic-stringable-nullsafe-access.php'], []);
+	}
+
 	public function testObjectShapes(): void
 	{
 		$tipText = 'Learn more: <fg=cyan>https://phpstan.org/blog/solving-phpstan-access-to-undefined-property</>';

tests/PHPStan/Rules/Properties/AccessPropertiesRuleTest.php

@@ -26,7 +26,7 @@ class AccessPropertiesRuleTest extends RuleTestCase
 	protected function getRule(): Rule
 	{
 		$reflectionProvider = self::createReflectionProvider();
-		return new AccessPropertiesRule(new AccessPropertiesCheck($reflectionProvider, new RuleLevelHelper($reflectionProvider, true, $this->checkThisOnly, $this->checkUnionTypes, false, false, false, true), new PhpVersion(PHP_VERSION_ID), true, $this->checkDynamicProperties));
+		return new AccessPropertiesRule(new AccessPropertiesCheck($reflectionProvider, new RuleLevelHelper($reflectionProvider, true, $this->checkThisOnly, $this->checkUnionTypes, false, false, false, true), new PhpVersion(PHP_VERSION_ID), true, $this->checkDynamicProperties, true));
 	}
 
 	public function testAccessProperties(): void
@@ -973,6 +973,84 @@ public function testBug8629(): void
 		$this->analyse([__DIR__ . '/data/bug-8629.php'], []);
 	}
 
+	public function testDynamicStringableAccess(): void
+	{
+		$this->checkThisOnly = false;
+		$this->checkUnionTypes = false;
+		$this->checkDynamicProperties = false;
+		$this->analyse([__DIR__ . '/data/dynamic-stringable-access.php'], [
+			// DynamicStringableAccess\Foo::testProperties()
+			[
+				'Property name for $this(DynamicStringableAccess\Foo) must be a string, but $this(DynamicStringableAccess\Foo) was given.',
+				13,
+			],
+			[
+				'Property name for DynamicStringableAccess\Foo must be a string, but $this(DynamicStringableAccess\Foo) was given.',
+				14,
+			],
+			[
+				'Property name for $this(DynamicStringableAccess\Foo) must be a string, but $this(DynamicStringableAccess\Foo) was given.',
+				15,
+			],
+			[
+				'Property name for $this(DynamicStringableAccess\Foo) must be a string, but $this(DynamicStringableAccess\Foo) was given.',
+				16,
+			],
+			[
+				'Property name for $this(DynamicStringableAccess\Foo) must be a string, but object was given.',
+				17,
+			],
+			[
+				'Property name for $this(DynamicStringableAccess\Foo) must be a string, but array was given.',
+				18,
+			],
+			// DynamicStringableAccess\Foo::testPropertyAssignments()
+			[
+				'Property name for $this(DynamicStringableAccess\Foo) must be a string, but $this(DynamicStringableAccess\Foo) was given.',
+				30,
+			],
+			[
+				'Property name for DynamicStringableAccess\Foo must be a string, but $this(DynamicStringableAccess\Foo) was given.',
+				31,
+			],
+			[
+				'Property name for $this(DynamicStringableAccess\Foo) must be a string, but object was given.',
+				32,
+			],
+		]);
+	}
+
+	#[RequiresPhp('>= 8.0')]
+	public function testDynamicStringableNullsafeAccess(): void
+	{
+		$this->checkThisOnly = false;
+		$this->checkUnionTypes = false;
+		$this->checkDynamicProperties = false;
+		$this->analyse([__DIR__ . '/data/dynamic-stringable-nullsafe-access.php'], [
+			// DynamicStringableNullsafeAccess\Foo::testNullsafePropertyFetch()
+			[
+				'Property name for $this(DynamicStringableNullsafeAccess\Foo) must be a string, but $this(DynamicStringableNullsafeAccess\Foo) was given.',
+				13,
+			],
+			[
+				'Property name for DynamicStringableNullsafeAccess\Foo must be a string, but $this(DynamicStringableNullsafeAccess\Foo) was given.',
+				14,
+			],
+			[
+				'Property name for $this(DynamicStringableNullsafeAccess\Foo) must be a string, but $this(DynamicStringableNullsafeAccess\Foo) was given.',
+				15,
+			],
+			[
+				'Property name for $this(DynamicStringableNullsafeAccess\Foo) must be a string, but $this(DynamicStringableNullsafeAccess\Foo) was given.',
+				16,
+			],
+			[
+				'Property name for $this(DynamicStringableNullsafeAccess\Foo) must be a string, but object was given.',
+				17,
+			],
+		]);
+	}
+
 	#[RequiresPhp('>= 8.0')]
 	public function testBug9694(): void
 	{

tests/PHPStan/Rules/Properties/data/dynamic-stringable-access.php

@@ -0,0 +1,42 @@
+<?php declare(strict_types = 1);
+
+namespace DynamicStringableAccess;
+
+use Stringable;
+
+final class Foo
+{
+	private self $var;
+
+	public function testProperties(string $name, Stringable $stringable, object $object, array $array): void
+	{
+		echo $this->{$this}->name;
+		echo $this->var->$this;
+		echo $this->$this->$name;
+		echo $this->$this->name;
+		echo $this->$object;
+		echo $this->$array;
+
+		echo $this->$name; // valid
+		echo $this->$stringable; // valid
+		echo $this->{1111}; // valid
+		echo $this->{true}; // valid
+		echo $this->{false}; // valid
+		echo $this->{null}; // valid
+	}
+
+	public function testPropertyAssignments(string $name, Stringable $stringable, object $object): void
+	{
+		$this->{$this} = $name;
+		$this->var->{$this} = $name;
+		$this->$object = $name;
+
+		$this->$name = $name; // valid
+		$this->$stringable = $name; // valid
+		$this->{1111} = $name; // valid
+		$this->{true} = $name; // valid
+		$this->{false} = $name; // valid
+		$this->{null} = $name; // valid
+	}
+
+}

tests/PHPStan/Rules/Properties/data/dynamic-stringable-nullsafe-access.php

@@ -0,0 +1,27 @@
+<?php declare(strict_types = 1); // lint >= 8.0
+
+namespace DynamicStringableNullsafeAccess;
+
+use Stringable;
+
+final class Foo
+{
+	private self $var;
+
+	public function testNullsafePropertyFetch(string $name, Stringable $stringable, object $object): void
+	{
+		echo $this?->{$this}?->name;
+		echo $this?->var?->$this;
+		echo $this?->$this?->$name;
+		echo $this?->$this?->name;
+		echo $this?->$object;
+
+		echo $this?->$name; // valid
+		echo $this?->$stringable; // valid
+		echo $this?->{1111}; // valid
+		echo $this?->{true}; // valid
+		echo $this?->{false}; // valid
+		echo $this?->{null}; // valid
+	}
+
+}