ClassConstantRule.php

<?php declare(strict_types = 1);

namespace PHPStan\Rules\Classes;

use PhpParser\Node;
use PhpParser\Node\Expr\ClassConstFetch;
use PHPStan\Analyser\NullsafeOperatorHelper;
use PHPStan\Analyser\Scope;
use PHPStan\Internal\SprintfHelper;
use PHPStan\Php\PhpVersion;
use PHPStan\Reflection\ReflectionProvider;
use PHPStan\Rules\ClassNameCheck;
use PHPStan\Rules\ClassNameNodePair;
use PHPStan\Rules\IdentifierRuleError;
use PHPStan\Rules\Rule;
use PHPStan\Rules\RuleErrorBuilder;
use PHPStan\Rules\RuleLevelHelper;
use PHPStan\Type\ErrorType;
use PHPStan\Type\StringType;
use PHPStan\Type\ThisType;
use PHPStan\Type\Type;
use PHPStan\Type\TypeCombinator;
use PHPStan\Type\VerbosityLevel;
use function array_map;
use function array_merge;
use function in_array;
use function sprintf;
use function strtolower;

/**
 * @implements Rule<Node\Expr\ClassConstFetch>
 */
final class ClassConstantRule implements Rule
{

	public function __construct(
		private ReflectionProvider $reflectionProvider,
		private RuleLevelHelper $ruleLevelHelper,
		private ClassNameCheck $classCheck,
		private PhpVersion $phpVersion,
	)
	{
	}

	public function getNodeType(): string
	{
		return ClassConstFetch::class;
	}

	public function processNode(Node $node, Scope $scope): array
	{
		$errors = [];
		if ($node->name instanceof Node\Identifier) {
			$constantNames = [$node->name->name];
		} else {
			$fetchType = $scope->getType($node->name);
			$constantNames = array_map(static fn ($type): string => $type->getValue(), $fetchType->getConstantStrings());
		}

		foreach ($constantNames as $constantName) {
			$errors = array_merge($errors, $this->processSingleClassConstFetch($scope, $node, $constantName));
		}

		return $errors;
	}

	/**
	 * @return list<IdentifierRuleError>
	 */
	private function processSingleClassConstFetch(Scope $scope, ClassConstFetch $node, string $constantName): array
	{
		$class = $node->class;
		$messages = [];
		if ($class instanceof Node\Name) {
			$className = (string) $class;
			$lowercasedClassName = strtolower($className);
			if (in_array($lowercasedClassName, ['self', 'static'], true)) {
				if (!$scope->isInClass()) {
					return [
						RuleErrorBuilder::message(sprintf('Using %s outside of class scope.', $className))
							->identifier(sprintf('outOfClass.%s', $lowercasedClassName))
							->build(),
					];
				}

				$classType = $scope->resolveTypeByName($class);
			} elseif ($lowercasedClassName === 'parent') {
				if (!$scope->isInClass()) {
					return [
						RuleErrorBuilder::message(sprintf('Using %s outside of class scope.', $className))
							->identifier(sprintf('outOfClass.%s', $lowercasedClassName))
							->build(),
					];
				}
				$currentClassReflection = $scope->getClassReflection();
				if ($currentClassReflection->getParentClass() === null) {
					return [
						RuleErrorBuilder::message(sprintf(
							'Access to parent::%s but %s does not extend any class.',
							$constantName,
							$currentClassReflection->getDisplayName(),
						))->identifier('class.noParent')->build(),
					];
				}
				$classType = $scope->resolveTypeByName($class);
			} else {
				if (!$this->reflectionProvider->hasClass($className)) {
					if ($scope->isInClassExists($className)) {
						return [];
					}

					if (strtolower($constantName) === 'class') {
						return [
							RuleErrorBuilder::message(sprintf('Class %s not found.', $className))
								->identifier('class.notFound')
								->discoveringSymbolsTip()
								->build(),
						];
					}

					return [
						RuleErrorBuilder::message(
							sprintf('Access to constant %s on an unknown class %s.', $constantName, $className),
						)
							->identifier('class.notFound')
							->discoveringSymbolsTip()
							->build(),
					];
				}

				$classType = $scope->resolveTypeByName($class);
				if (strtolower($constantName) !== 'class') {
					foreach ($classType->getObjectClassReflections() as $classTypeReflection) {
						if (!$classTypeReflection->isTrait()) {
							continue;
						}

						return [
							RuleErrorBuilder::message(sprintf(
								'Cannot access constant %s on trait %s.',
								$constantName,
								$classTypeReflection->getDisplayName(),
							))->identifier('classConstant.onTrait')->build(),
						];
					}
				}

				$messages = $this->classCheck->checkClassNames([new ClassNameNodePair($className, $class)]);
			}

			if (strtolower($constantName) === 'class') {
				return $messages;
			}
		} else {
			$classTypeResult = $this->ruleLevelHelper->findTypeToCheck(
				$scope,
				NullsafeOperatorHelper::getNullsafeShortcircuitedExprRespectingScope($scope, $class),
				sprintf('Access to constant %s on an unknown class %%s.', SprintfHelper::escapeFormatString($constantName)),
				static fn (Type $type): bool => $type->canAccessConstants()->yes() && $type->hasConstant($constantName)->yes(),
			);
			$classType = $classTypeResult->getType();
			if ($classType instanceof ErrorType) {
				return $classTypeResult->getUnknownClassErrors();
			}

			if (strtolower($constantName) === 'class') {
				if (!$this->phpVersion->supportsClassConstantOnExpression()) {
					return [
						RuleErrorBuilder::message('Accessing ::class constant on an expression is supported only on PHP 8.0 and later.')
							->identifier('classConstant.notSupported')
							->nonIgnorable()
							->build(),
					];
				}

				if (!$class instanceof Node\Scalar\String_ && $classType->isString()->yes()) {
					return [
						RuleErrorBuilder::message('Accessing ::class constant on a dynamic string is not supported in PHP.')
							->identifier('classConstant.dynamicString')
							->nonIgnorable()
							->build(),
					];
				}
			}
		}

		if ($classType->isString()->yes()) {
			return $messages;
		}

		$typeForDescribe = $classType;
		if ($classType instanceof ThisType) {
			$typeForDescribe = $classType->getStaticObjectType();
		}
		$classType = TypeCombinator::remove($classType, new StringType());

		if (!$classType->canAccessConstants()->yes()) {
			return array_merge($messages, [
				RuleErrorBuilder::message(sprintf(
					'Cannot access constant %s on %s.',
					$constantName,
					$typeForDescribe->describe(VerbosityLevel::typeOnly()),
				))->identifier('classConstant.nonObject')->build(),
			]);
		}

		if (strtolower($constantName) === 'class' || $scope->hasExpressionType($node)->yes()) {
			return $messages;
		}

		if (!$classType->hasConstant($constantName)->yes()) {
			return array_merge($messages, [
				RuleErrorBuilder::message(sprintf(
					'Access to undefined constant %s::%s.',
					$typeForDescribe->describe(VerbosityLevel::typeOnly()),
					$constantName,
				))->identifier('classConstant.notFound')->build(),
			]);
		}

		$constantReflection = $classType->getConstant($constantName);
		if (!$scope->canAccessConstant($constantReflection)) {
			return array_merge($messages, [
				RuleErrorBuilder::message(sprintf(
					'Access to %s constant %s of class %s.',
					$constantReflection->isPrivate() ? 'private' : 'protected',
					$constantName,
					$constantReflection->getDeclaringClass()->getDisplayName(),
				))->identifier(sprintf(
					'classConstant.%s',
					$constantReflection->isPrivate() ? 'private' : 'protected',
				))->build(),
			]);
		}

		return $messages;
	}

}