FunctionDefinitionCheck.php

<?php declare(strict_types = 1);

namespace PHPStan\Rules;

use PhpParser\Node;
use PhpParser\Node\ComplexType;
use PhpParser\Node\Expr\ConstFetch;
use PhpParser\Node\Expr\Variable;
use PhpParser\Node\FunctionLike;
use PhpParser\Node\Identifier;
use PhpParser\Node\IntersectionType;
use PhpParser\Node\Name;
use PhpParser\Node\NullableType;
use PhpParser\Node\Param;
use PhpParser\Node\Stmt\ClassMethod;
use PhpParser\Node\Stmt\Function_;
use PhpParser\Node\UnionType;
use PHPStan\Analyser\Scope;
use PHPStan\DependencyInjection\AutowiredParameter;
use PHPStan\DependencyInjection\AutowiredService;
use PHPStan\Node\Printer\NodeTypePrinter;
use PHPStan\Php\PhpVersion;
use PHPStan\Reflection\ExtendedParameterReflection;
use PHPStan\Reflection\ExtendedParametersAcceptor;
use PHPStan\Reflection\ParameterReflection;
use PHPStan\Reflection\ParametersAcceptor;
use PHPStan\Reflection\Php\PhpFunctionFromParserNodeReflection;
use PHPStan\Reflection\Php\PhpMethodFromParserNodeReflection;
use PHPStan\Reflection\ReflectionProvider;
use PHPStan\Rules\PhpDoc\UnresolvableTypeHelper;
use PHPStan\ShouldNotHappenException;
use PHPStan\Type\ConditionalTypeForParameter;
use PHPStan\Type\Generic\TemplateType;
use PHPStan\Type\NeverType;
use PHPStan\Type\NonexistentParentClassType;
use PHPStan\Type\ParserNodeTypeToPHPStanType;
use PHPStan\Type\Type;
use PHPStan\Type\TypeTraverser;
use PHPStan\Type\VerbosityLevel;
use function array_filter;
use function array_keys;
use function array_map;
use function array_merge;
use function array_slice;
use function count;
use function implode;
use function in_array;
use function is_string;
use function sprintf;
use function strtolower;

#[AutowiredService]
final class FunctionDefinitionCheck
{

	public function __construct(
		private ReflectionProvider $reflectionProvider,
		private ClassNameCheck $classCheck,
		private UnresolvableTypeHelper $unresolvableTypeHelper,
		private PhpVersion $phpVersion,
		#[AutowiredParameter]
		private bool $checkClassCaseSensitivity,
		#[AutowiredParameter]
		private bool $checkThisOnly,
		#[AutowiredParameter(ref: '%featureToggles.checkImportedClassNameCase%')]
		private bool $checkImportedClassNameCase,
	)
	{
	}

	/**
	 * @return list<IdentifierRuleError>
	 */
	public function checkFunction(
		Scope $scope,
		Function_ $function,
		PhpFunctionFromParserNodeReflection $functionReflection,
		string $parameterMessage,
		string $returnMessage,
		string $unionTypesMessage,
		string $templateTypeMissingInParameterMessage,
		string $unresolvableParameterTypeMessage,
		string $unresolvableReturnTypeMessage,
		string $noDiscardVoidReturnMessage,
	): array
	{
		return $this->checkParametersAcceptor(
			$scope,
			$functionReflection,
			$function,
			$parameterMessage,
			$returnMessage,
			$unionTypesMessage,
			$templateTypeMissingInParameterMessage,
			$unresolvableParameterTypeMessage,
			$unresolvableReturnTypeMessage,
			$noDiscardVoidReturnMessage,
		);
	}

	/**
	 * @param Node\Param[] $parameters
	 * @param Node\Identifier|Node\Name|Node\ComplexType|null $returnTypeNode
	 * @param Node\AttributeGroup[] $attribGroups
	 * @return list<IdentifierRuleError>
	 */
	public function checkAnonymousFunction(
		Scope $scope,
		array $parameters,
		$returnTypeNode,
		array $attribGroups,
		string $parameterMessage,
		string $returnMessage,
		string $unionTypesMessage,
		string $unresolvableParameterTypeMessage,
		string $unresolvableReturnTypeMessage,
		string $noDiscardReturnTypeMessage,
	): array
	{
		$errors = [];
		$unionTypeReported = false;
		foreach ($parameters as $i => $param) {
			if ($param->type === null) {
				continue;
			}
			if (
				!$unionTypeReported
				&& $param->type instanceof UnionType
				&& !$this->phpVersion->supportsNativeUnionTypes()
			) {
				$errors[] = RuleErrorBuilder::message($unionTypesMessage)
					->line($param->getStartLine())
					->identifier('parameter.unionTypeNotSupported')
					->nonIgnorable()
					->build();
				$unionTypeReported = true;
			}

			if (!$param->var instanceof Variable || !is_string($param->var->name)) {
				throw new ShouldNotHappenException();
			}

			$implicitlyNullableTypeError = $this->checkImplicitlyNullableType(
				$param->type,
				$param->default,
				$i + 1,
				$param->getStartLine(),
				$param->var->name,
			);
			if ($implicitlyNullableTypeError !== null) {
				$errors[] = $implicitlyNullableTypeError;
			}

			$type = $scope->getFunctionType($param->type, false, false);
			$unresolvableType = $this->phpVersion->supportsPureIntersectionTypes()
				? $this->unresolvableTypeHelper->getUnresolvableType($type)
				: null;
			if ($unresolvableType !== null) {
				$errorBuilder = RuleErrorBuilder::message(sprintf($unresolvableParameterTypeMessage, $param->var->name))
					->line($param->type->getStartLine())
					->identifier('parameter.unresolvableNativeType')
					->nonIgnorable();
				foreach ($unresolvableType->reasons as $reason) {
					$errorBuilder->addTip($reason);
				}
				$errors[] = $errorBuilder->build();
			}

			foreach ($type->getReferencedClasses() as $class) {
				if (!$this->reflectionProvider->hasClass($class)) {
					$errors[] = RuleErrorBuilder::message(sprintf($parameterMessage, $param->var->name, $class))
					->line($param->type->getStartLine())
					->identifier('class.notFound')
					->build();
					continue;
				}

				$classReflection = $this->reflectionProvider->getClass($class);
				if ($classReflection->isTrait()) {
					$errors[] = RuleErrorBuilder::message(sprintf($parameterMessage, $param->var->name, $class))
						->line($param->type->getStartLine())
						->identifier('parameter.trait')
						->build();
					continue;
				}
			}

			$anonParamOriginalCasePairs = $this->getOriginalClassNamePairsFromTypeNode($param->type);

			$errors = array_merge(
				$errors,
				$this->classCheck->checkClassNames($scope, array_map(static function (string $class) use ($param, $anonParamOriginalCasePairs): ClassNameNodePair {
					$lowerClass = strtolower($class);
					if (isset($anonParamOriginalCasePairs[$lowerClass])) {
						return $anonParamOriginalCasePairs[$lowerClass];
					}
					return new ClassNameNodePair($class, $param->type);
				}, $type->getReferencedClasses()), ClassNameUsageLocation::from(ClassNameUsageLocation::PARAMETER_TYPE, [
					'parameterName' => $param->var->name,
					'isInAnonymousFunction' => true,
				]), $this->checkClassCaseSensitivity),
			);
		}

		if ($this->phpVersion->deprecatesRequiredParameterAfterOptional()) {
			$errors = array_merge($errors, $this->checkRequiredParameterAfterOptional($parameters));
		}

		if ($returnTypeNode === null) {
			return $errors;
		}
		if (
			$returnTypeNode instanceof Identifier
			&& in_array($returnTypeNode->toLowerString(), ['void', 'never'], true)
		) {
			foreach ($attribGroups as $attribGroup) {
				foreach ($attribGroup->attrs as $attrib) {
					if (strtolower($attrib->name->name) === 'nodiscard') {
						$errors[] = RuleErrorBuilder::message(sprintf($noDiscardReturnTypeMessage, $returnTypeNode->toString()))
							->line($returnTypeNode->getStartLine())
							->identifier('attribute.target')
							->build();
						break 2;
					}
				}
			}
		}

		if (
			!$unionTypeReported
			&& $returnTypeNode instanceof UnionType
			&& !$this->phpVersion->supportsNativeUnionTypes()
		) {
			$errors[] = RuleErrorBuilder::message($unionTypesMessage)
				->line($returnTypeNode->getStartLine())
				->identifier('return.unionTypeNotSupported')
				->nonIgnorable()
				->build();
		}

		$returnType = $scope->getFunctionType($returnTypeNode, false, false);
		$unresolvableReturnType = $this->phpVersion->supportsPureIntersectionTypes()
			? $this->unresolvableTypeHelper->getUnresolvableType($returnType)
			: null;
		if ($unresolvableReturnType !== null) {
			$errorBuilder = RuleErrorBuilder::message($unresolvableReturnTypeMessage)
				->line($returnTypeNode->getStartLine())
				->identifier('return.unresolvableNativeType')
				->nonIgnorable();
			foreach ($unresolvableReturnType->reasons as $reason) {
				$errorBuilder->addTip($reason);
			}
			$errors[] = $errorBuilder->build();
		}

		foreach ($returnType->getReferencedClasses() as $returnTypeClass) {
			if (!$this->reflectionProvider->hasClass($returnTypeClass)) {
				$errors[] = RuleErrorBuilder::message(sprintf($returnMessage, $returnTypeClass))
					->line($returnTypeNode->getStartLine())
					->identifier('class.notFound')
					->build();
				continue;
			}

			if ($this->reflectionProvider->getClass($returnTypeClass)->isTrait()) {
				$errors[] = RuleErrorBuilder::message(sprintf($returnMessage, $returnTypeClass))
					->line($returnTypeNode->getStartLine())
					->identifier('return.trait')
					->build();
				continue;
			}
		}

		$anonReturnOriginalCasePairs = $this->getOriginalClassNamePairsFromTypeNode($returnTypeNode);

		$errors = array_merge(
			$errors,
			$this->classCheck->checkClassNames($scope, array_map(static function (string $class) use ($returnTypeNode, $anonReturnOriginalCasePairs): ClassNameNodePair {
				$lowerClass = strtolower($class);
				if (isset($anonReturnOriginalCasePairs[$lowerClass])) {
					return $anonReturnOriginalCasePairs[$lowerClass];
				}
				return new ClassNameNodePair($class, $returnTypeNode);
			}, $returnType->getReferencedClasses()), ClassNameUsageLocation::from(ClassNameUsageLocation::RETURN_TYPE, [
				'isInAnonymousFunction' => true,
			]), $this->checkClassCaseSensitivity),
		);

		return $errors;
	}

	/**
	 * @return list<IdentifierRuleError>
	 */
	public function checkClassMethod(
		Scope $scope,
		PhpMethodFromParserNodeReflection $methodReflection,
		ClassMethod|Node\PropertyHook $methodNode,
		string $parameterMessage,
		string $returnMessage,
		string $unionTypesMessage,
		string $templateTypeMissingInParameterMessage,
		string $unresolvableParameterTypeMessage,
		string $unresolvableReturnTypeMessage,
		string $selfOutMessage,
		string $noDiscardVoidReturnMessage,
	): array
	{
		$errors = $this->checkParametersAcceptor(
			$scope,
			$methodReflection,
			$methodNode,
			$parameterMessage,
			$returnMessage,
			$unionTypesMessage,
			$templateTypeMissingInParameterMessage,
			$unresolvableParameterTypeMessage,
			$unresolvableReturnTypeMessage,
			$noDiscardVoidReturnMessage,
		);

		$selfOutType = $methodReflection->getSelfOutType();
		if ($selfOutType !== null) {
			$selfOutTypeReferencedClasses = $selfOutType->getReferencedClasses();

			foreach ($selfOutTypeReferencedClasses as $class) {
				if (!$this->reflectionProvider->hasClass($class)) {
					$errors[] = RuleErrorBuilder::message(sprintf($selfOutMessage, $class))
						->line($methodNode->getStartLine())
						->identifier('class.notFound')
						->build();
					continue;
				}
				if (!$this->reflectionProvider->getClass($class)->isTrait()) {
					continue;
				}

				$errors[] = RuleErrorBuilder::message(sprintf($selfOutMessage, $class))
					->line($methodNode->getStartLine())
					->identifier('selfOut.trait')
					->build();
			}

			$errors = array_merge(
				$errors,
				$this->classCheck->checkClassNames(
					$scope,
					array_map(static fn (string $class): ClassNameNodePair => new ClassNameNodePair($class, $methodNode), $selfOutTypeReferencedClasses),
					ClassNameUsageLocation::from(ClassNameUsageLocation::PHPDOC_TAG_SELF_OUT),
					$this->checkClassCaseSensitivity,
				),
			);
		}

		return $errors;
	}

	/**
	 * @return list<IdentifierRuleError>
	 */
	private function checkParametersAcceptor(
		Scope $scope,
		PhpMethodFromParserNodeReflection|PhpFunctionFromParserNodeReflection $parametersAcceptor,
		FunctionLike $functionNode,
		string $parameterMessage,
		string $returnMessage,
		string $unionTypesMessage,
		string $templateTypeMissingInParameterMessage,
		string $unresolvableParameterTypeMessage,
		string $unresolvableReturnTypeMessage,
		string $noDiscardReturnTypeMessage,
	): array
	{
		$errors = [];
		$parameterNodes = $functionNode->getParams();
		if (!$this->phpVersion->supportsNativeUnionTypes()) {
			$unionTypeReported = false;
			foreach ($parameterNodes as $parameterNode) {
				if (!$parameterNode->type instanceof UnionType) {
					continue;
				}

				$errors[] = RuleErrorBuilder::message($unionTypesMessage)
					->line($parameterNode->getStartLine())
					->identifier('parameter.unionTypeNotSupported')
					->nonIgnorable()
					->build();
				$unionTypeReported = true;
				break;
			}

			if (!$unionTypeReported && $functionNode->getReturnType() instanceof UnionType) {
				$errors[] = RuleErrorBuilder::message($unionTypesMessage)
					->line($functionNode->getReturnType()->getStartLine())
					->identifier('return.unionTypeNotSupported')
					->nonIgnorable()
					->build();
			}
		}

		foreach ($parameterNodes as $i => $parameterNode) {
			if (!$parameterNode->var instanceof Variable || !is_string($parameterNode->var->name)) {
				throw new ShouldNotHappenException();
			}
			$implicitlyNullableTypeError = $this->checkImplicitlyNullableType($parameterNode->type, $parameterNode->default, $i + 1, $parameterNode->getStartLine(), $parameterNode->var->name);
			if ($implicitlyNullableTypeError === null) {
				continue;
			}

			$errors[] = $implicitlyNullableTypeError;
		}

		if ($this->phpVersion->deprecatesRequiredParameterAfterOptional()) {
			$errors = array_merge($errors, $this->checkRequiredParameterAfterOptional($parameterNodes));
		}

		$returnTypeNode = $functionNode->getReturnType() ?? $functionNode;
		foreach ($parametersAcceptor->getParameters() as $parameter) {
			$referencedClasses = $this->getParameterReferencedClasses($parameter);
			$parameterNode = null;
			$parameterNodeCallback = function () use ($parameter, $parameterNodes, &$parameterNode): Param {
				if ($parameterNode === null) {
					$parameterNode = $this->getParameterNode($parameter->getName(), $parameterNodes);
				}

				return $parameterNode;
			};
			$parameterVar = $parameterNodeCallback()->var;
			if (!$parameterVar instanceof Variable || !is_string($parameterVar->name)) {
				throw new ShouldNotHappenException();
			}
			$unresolvableType = $this->phpVersion->supportsPureIntersectionTypes()
				? $this->unresolvableTypeHelper->getUnresolvableType($parameter->getNativeType())
				: null;
			if ($unresolvableType !== null) {
				$errorBuilder = RuleErrorBuilder::message(sprintf($unresolvableParameterTypeMessage, $parameterVar->name))
					->line($parameterNodeCallback()->getStartLine())
					->identifier('parameter.unresolvableNativeType')
					->nonIgnorable();
				foreach ($unresolvableType->reasons as $reason) {
					$errorBuilder->addTip($reason);
				}
				$errors[] = $errorBuilder->build();
			}
			foreach ($referencedClasses as $class) {
				if (!$this->reflectionProvider->hasClass($class)) {
					$errors[] = RuleErrorBuilder::message(sprintf(
						$parameterMessage,
						$parameter->getName(),
						$class,
					))
						->line($parameterNodeCallback()->getStartLine())
						->identifier('class.notFound')
						->build();
					continue;
				}
				if (!$this->reflectionProvider->getClass($class)->isTrait()) {
					continue;
				}

				$errors[] = RuleErrorBuilder::message(sprintf(
					$parameterMessage,
					$parameter->getName(),
					$class,
				))
					->line($parameterNodeCallback()->getStartLine())
					->identifier('parameter.trait')
					->build();
			}

			$locationData = [
				'parameterName' => $parameter->getName(),
			];
			if ($parametersAcceptor instanceof PhpMethodFromParserNodeReflection) {
				$locationData['method'] = $parametersAcceptor;
				if (!$parametersAcceptor->getDeclaringClass()->isAnonymous()) {
					$locationData['currentClassName'] = $parametersAcceptor->getDeclaringClass()->getName();
				}
			} else {
				$locationData['function'] = $parametersAcceptor;
			}

			$originalCasePairs = $this->getOriginalClassNamePairsFromTypeNode($parameterNodeCallback()->type);

			$errors = array_merge(
				$errors,
				$this->classCheck->checkClassNames(
					$scope,
					array_map(static function (string $class) use ($parameterNodeCallback, $originalCasePairs): ClassNameNodePair {
						$lowerClass = strtolower($class);
						if (isset($originalCasePairs[$lowerClass])) {
							return $originalCasePairs[$lowerClass];
						}
						return new ClassNameNodePair($class, $parameterNodeCallback());
					}, $referencedClasses),
					ClassNameUsageLocation::from(ClassNameUsageLocation::PARAMETER_TYPE, $locationData),
					$this->checkClassCaseSensitivity,
				),
			);
			if (!($parameter->getType() instanceof NonexistentParentClassType)) {
				continue;
			}

			$errors[] = RuleErrorBuilder::message(sprintf($parameterMessage, $parameter->getName(), $parameter->getType()->describe(VerbosityLevel::typeOnly())))
				->line($parameterNodeCallback()->getStartLine())
				->identifier('parameter.noParent')
				->build();
		}

		if ($this->phpVersion->supportsPureIntersectionTypes() && $functionNode->getReturnType() !== null) {
			$nativeReturnType = ParserNodeTypeToPHPStanType::resolve($functionNode->getReturnType(), $scope->isInClass() ? $scope->getClassReflection() : null);
			$unresolvableType = $this->unresolvableTypeHelper->getUnresolvableType($nativeReturnType);
			if ($unresolvableType !== null) {
				$errorBuilder = RuleErrorBuilder::message($unresolvableReturnTypeMessage)
					->nonIgnorable()
					->line($returnTypeNode->getStartLine())
					->identifier('return.unresolvableNativeType');
				foreach ($unresolvableType->reasons as $reason) {
					$errorBuilder->addTip($reason);
				}
				$errors[] = $errorBuilder->build();
			}
		}
		if ($parametersAcceptor->mustUseReturnValue()->yes()) {
			$returnType = $parametersAcceptor->getReturnType();
			if (
				$returnType->isVoid()->yes()
				|| ($returnType instanceof NeverType && $returnType->isExplicit())
			) {
				$errors[] = RuleErrorBuilder::message(sprintf($noDiscardReturnTypeMessage, $returnType->describe(VerbosityLevel::typeOnly())))
					->line($returnTypeNode->getStartLine())
					->identifier('attribute.target')
					->build();
			}
		}

		$returnTypeReferencedClasses = $this->getReturnTypeReferencedClasses($parametersAcceptor);

		foreach ($returnTypeReferencedClasses as $class) {
			if (!$this->reflectionProvider->hasClass($class)) {
				$errors[] = RuleErrorBuilder::message(sprintf($returnMessage, $class))
					->line($returnTypeNode->getStartLine())
					->identifier('class.notFound')
					->build();
				continue;
			}
			if (!$this->reflectionProvider->getClass($class)->isTrait()) {
				continue;
			}

			$errors[] = RuleErrorBuilder::message(sprintf($returnMessage, $class))
				->line($returnTypeNode->getStartLine())
				->identifier('return.trait')
				->build();
		}

		$locationData = [];
		if ($parametersAcceptor instanceof PhpMethodFromParserNodeReflection) {
			$locationData['method'] = $parametersAcceptor;
			if (!$parametersAcceptor->getDeclaringClass()->isAnonymous()) {
				$locationData['currentClassName'] = $parametersAcceptor->getDeclaringClass()->getName();
			}
		} else {
			$locationData['function'] = $parametersAcceptor;
		}

		$returnOriginalCasePairs = $this->getOriginalClassNamePairsFromTypeNode($functionNode->getReturnType());

		$errors = array_merge(
			$errors,
			$this->classCheck->checkClassNames(
				$scope,
				array_map(static function (string $class) use ($returnTypeNode, $returnOriginalCasePairs): ClassNameNodePair {
					$lowerClass = strtolower($class);
					if (isset($returnOriginalCasePairs[$lowerClass])) {
						return $returnOriginalCasePairs[$lowerClass];
					}
					return new ClassNameNodePair($class, $returnTypeNode);
				}, $returnTypeReferencedClasses),
				ClassNameUsageLocation::from(ClassNameUsageLocation::RETURN_TYPE, $locationData),
				$this->checkClassCaseSensitivity,
			),
		);
		if ($parametersAcceptor->getReturnType() instanceof NonexistentParentClassType) {
			$errors[] = RuleErrorBuilder::message(sprintf($returnMessage, $parametersAcceptor->getReturnType()->describe(VerbosityLevel::typeOnly())))
				->line($returnTypeNode->getStartLine())
				->identifier('return.noParent')
				->build();
		}

		$templateTypeMap = $parametersAcceptor->getTemplateTypeMap();
		$templateTypes = $templateTypeMap->getTypes();
		if (count($templateTypes) > 0) {
			foreach ($parametersAcceptor->getParameters() as $parameter) {
				TypeTraverser::map($parameter->getType(), static function (Type $type, callable $traverse) use (&$templateTypes): Type {
					if ($type instanceof TemplateType) {
						unset($templateTypes[$type->getName()]);
						return $traverse($type);
					}

					return $traverse($type);
				});
			}

			$returnType = $parametersAcceptor->getReturnType();
			if ($returnType instanceof ConditionalTypeForParameter && !$returnType->isNegated()) {
				TypeTraverser::map($returnType, static function (Type $type, callable $traverse) use (&$templateTypes): Type {
					if ($type instanceof TemplateType) {
						unset($templateTypes[$type->getName()]);
						return $traverse($type);
					}

					return $traverse($type);
				});
			}

			foreach (array_keys($templateTypes) as $templateTypeName) {
				$errors[] = RuleErrorBuilder::message(sprintf($templateTypeMissingInParameterMessage, $templateTypeName))
					->identifier('method.templateTypeNotInParameter')
					->build();
			}
		}

		return $errors;
	}

	/**
	 * @param Param[] $parameterNodes
	 * @return list<IdentifierRuleError>
	 */
	private function checkRequiredParameterAfterOptional(array $parameterNodes): array
	{
		/** @var string|null $optionalParameter */
		$optionalParameter = null;
		$errors = [];
		$targetPhpVersion = null;
		foreach ($parameterNodes as $parameterNode) {
			if (!$parameterNode->var instanceof Variable) {
				throw new ShouldNotHappenException();
			}
			if (!is_string($parameterNode->var->name)) {
				throw new ShouldNotHappenException();
			}
			$parameterName = $parameterNode->var->name;
			if ($optionalParameter !== null && $parameterNode->default === null && !$parameterNode->variadic) {
				$errors[] = RuleErrorBuilder::message(
					sprintf(
						'Deprecated in PHP %s: Required parameter $%s follows optional parameter $%s.',
						$targetPhpVersion ?? '8.0',
						$parameterName,
						$optionalParameter,
					),
				)->line($parameterNode->getStartLine())
					->identifier('parameter.requiredAfterOptional')
					->build();
				$targetPhpVersion = null;
				continue;
			}
			if ($parameterNode->default === null) {
				continue;
			}
			if ($parameterNode->type === null) {
				$optionalParameter = $parameterName;
				continue;
			}

			$defaultValue = $parameterNode->default;
			if (!$defaultValue instanceof ConstFetch) {
				$optionalParameter = $parameterName;
				continue;
			}

			$constantName = $defaultValue->name->toLowerString();
			if ($constantName === 'null') {
				if (!$this->phpVersion->deprecatesRequiredParameterAfterOptionalNullableAndDefaultNull()) {
					continue;
				}

				$parameterNodeType = $parameterNode->type;

				if ($parameterNodeType instanceof NullableType) {
					$targetPhpVersion = '8.1';
				}

				if ($this->phpVersion->deprecatesRequiredParameterAfterOptionalUnionOrMixed()) {
					$types = [];

					if ($parameterNodeType instanceof UnionType) {
						$types = $parameterNodeType->types;
					} elseif ($parameterNodeType instanceof Identifier) {
						$types = [$parameterNodeType];
					}

					$nullOrMixed = array_filter($types, static fn (Identifier|Name|IntersectionType $type): bool => $type instanceof Identifier && (in_array($type->name, ['null', 'mixed'], true)));

					if (0 < count($nullOrMixed)) {
						$targetPhpVersion = '8.3';
					}
				}

				if ($targetPhpVersion === null) {
					continue;
				}
			}

			$optionalParameter = $parameterName;
		}

		return $errors;
	}

	/**
	 * @param Param[] $parameterNodes
	 */
	private function getParameterNode(
		string $parameterName,
		array $parameterNodes,
	): Param
	{
		foreach ($parameterNodes as $param) {
			if ($param->var instanceof Node\Expr\Error) {
				continue;
			}

			if (!is_string($param->var->name)) {
				continue;
			}

			if ($param->var->name === $parameterName) {
				return $param;
			}
		}

		throw new ShouldNotHappenException(sprintf('Parameter %s not found.', $parameterName));
	}

	/**
	 * @return non-empty-string[]
	 */
	private function getParameterReferencedClasses(ParameterReflection $parameter): array
	{
		if (!$parameter instanceof ExtendedParameterReflection) {
			return $parameter->getType()->getReferencedClasses();
		}

		if ($this->checkThisOnly) {
			return $parameter->getNativeType()->getReferencedClasses();
		}

		$moreClasses = [];
		if ($parameter->getOutType() !== null) {
			$moreClasses = array_merge($moreClasses, $parameter->getOutType()->getReferencedClasses());
		}
		if ($parameter->getClosureThisType() !== null) {
			$moreClasses = array_merge($moreClasses, $parameter->getClosureThisType()->getReferencedClasses());
		}

		return array_merge(
			$parameter->getNativeType()->getReferencedClasses(),
			$parameter->getPhpDocType()->getReferencedClasses(),
			$moreClasses,
		);
	}

	/**
	 * @return non-empty-string[]
	 */
	private function getReturnTypeReferencedClasses(ParametersAcceptor $parametersAcceptor): array
	{
		if (!$parametersAcceptor instanceof ExtendedParametersAcceptor) {
			return $parametersAcceptor->getReturnType()->getReferencedClasses();
		}

		if ($this->checkThisOnly) {
			return $parametersAcceptor->getNativeReturnType()->getReferencedClasses();
		}

		return array_merge(
			$parametersAcceptor->getNativeReturnType()->getReferencedClasses(),
			$parametersAcceptor->getPhpDocReturnType()->getReferencedClasses(),
		);
	}

	private function checkImplicitlyNullableType(
		Identifier|Name|ComplexType|null $type,
		?Node\Expr $default,
		int $order,
		int $line,
		string $name,
	): ?IdentifierRuleError
	{
		if (!$default instanceof ConstFetch) {
			return null;
		}

		if ($default->name->toLowerString() !== 'null') {
			return null;
		}

		if ($type === null) {
			return null;
		}

		if ($type instanceof NullableType || $type instanceof IntersectionType) {
			return null;
		}

		if (!$this->phpVersion->deprecatesImplicitlyNullableParameterTypes()) {
			return null;
		}

		if ($type instanceof Identifier && strtolower($type->name) === 'mixed') {
			return null;
		}

		if ($type instanceof Identifier && strtolower($type->name) === 'null') {
			return null;
		}
		if ($type instanceof Name && $type->toLowerString() === 'null') {
			return null;
		}

		if ($type instanceof UnionType) {
			foreach ($type->types as $innerType) {
				if ($innerType instanceof Identifier && strtolower($innerType->name) === 'null') {
					return null;
				}
			}
		}

		return RuleErrorBuilder::message(sprintf(
			'Deprecated in PHP 8.4: Parameter #%d $%s (%s) is implicitly nullable via default value null.',
			$order,
			$name,
			NodeTypePrinter::printType($type),
		))->line($line)
			->identifier('parameter.implicitlyNullable')
			->build();
	}

	/**
	 * @return array<string, ClassNameNodePair>
	 */
	private function getOriginalClassNamePairsFromTypeNode(Identifier|Name|ComplexType|null $typeNode): array
	{
		if ($typeNode === null) {
			return [];
		}

		if ($typeNode instanceof Name) {
			$resolvedName = $typeNode->toString();
			if ($this->checkImportedClassNameCase) {
				$nameAsWritten = ClassCaseSensitivityCheck::getNameAsWritten($typeNode);
				if ($nameAsWritten === $resolvedName) {
					return [];
				}

				return [strtolower($resolvedName) => new ClassNameNodePair($nameAsWritten, $typeNode)];
			}

			$originalName = $typeNode->getAttribute('originalName');
			if (!$originalName instanceof Name) {
				return [];
			}

			$originalPartsCount = count($originalName->getParts());
			$resolvedParts = $typeNode->getParts();
			$resolvedPartsCount = count($resolvedParts);

			// the original name takes over the last parts of the resolved name,
			// the parts it does not cover stay as resolved
			$prefixParts = $originalPartsCount <= $resolvedPartsCount
				? array_slice($resolvedParts, 0, $resolvedPartsCount - $originalPartsCount)
				: [];
			$prefix = $prefixParts === [] ? '' : implode('\\', $prefixParts) . '\\';
			$originalCaseClassName = $prefix . $originalName->toString();

			if ($originalCaseClassName === $resolvedName) {
				return [];
			}

			return [strtolower($resolvedName) => new ClassNameNodePair($originalCaseClassName, $typeNode)];
		}

		if ($typeNode instanceof NullableType) {
			return $this->getOriginalClassNamePairsFromTypeNode($typeNode->type);
		}

		if ($typeNode instanceof UnionType || $typeNode instanceof IntersectionType) {
			$pairs = [];
			foreach ($typeNode->types as $innerType) {
				$pairs += $this->getOriginalClassNamePairsFromTypeNode($innerType);
			}
			return $pairs;
		}

		return [];
	}

}