Add null to return type of Iterator::current(), Iterator::key(), and Generator::send() with valid() narrowing

src/Type/Php/GeneratorSendReturnTypeExtension.php

@@ -0,0 +1,58 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Type\Php;
+
+use Generator;
+use PhpParser\Node\Expr\MethodCall;
+use PHPStan\Analyser\Scope;
+use PHPStan\DependencyInjection\AutowiredService;
+use PHPStan\Reflection\ExtendedParametersAcceptor;
+use PHPStan\Reflection\MethodReflection;
+use PHPStan\Reflection\ParametersAcceptorSelector;
+use PHPStan\Type\BenevolentUnionType;
+use PHPStan\Type\DynamicMethodReturnTypeExtension;
+use PHPStan\Type\NullType;
+use PHPStan\Type\Type;
+use PHPStan\Type\TypeCombinator;
+use PHPStan\Type\TypeUtils;
+
+#[AutowiredService]
+final class GeneratorSendReturnTypeExtension implements DynamicMethodReturnTypeExtension
+{
+
+	public function getClass(): string
+	{
+		return Generator::class;
+	}
+
+	public function isMethodSupported(MethodReflection $methodReflection): bool
+	{
+		return $methodReflection->getName() === 'send';
+	}
+
+	public function getTypeFromMethodCall(MethodReflection $methodReflection, MethodCall $methodCall, Scope $scope): Type
+	{
+		$parametersAcceptor = ParametersAcceptorSelector::selectFromArgs(
+			$scope,
+			$methodCall->getArgs(),
+			$methodReflection->getVariants(),
+		);
+
+		$returnType = $parametersAcceptor->getReturnType();
+
+		if ($parametersAcceptor instanceof ExtendedParametersAcceptor) {
+			$nativeReturnType = $parametersAcceptor->getNativeReturnType();
+			if ($nativeReturnType->isSuperTypeOf(new NullType())->no()) {
+				return $returnType;
+			}
+		}
+
+		$result = TypeCombinator::addNull($returnType);
+		if ($returnType instanceof BenevolentUnionType && !($result instanceof BenevolentUnionType)) {
+			$result = TypeUtils::toBenevolentUnion($result);
+		}
+
+		return $result;
+	}
+
+}

src/Type/Php/IteratorCurrentReturnTypeExtension.php

@@ -0,0 +1,59 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Type\Php;
+
+use Iterator;
+use PhpParser\Node\Expr\MethodCall;
+use PHPStan\Analyser\Scope;
+use PHPStan\DependencyInjection\AutowiredService;
+use PHPStan\Reflection\ExtendedParametersAcceptor;
+use PHPStan\Reflection\MethodReflection;
+use PHPStan\Reflection\ParametersAcceptorSelector;
+use PHPStan\Type\BenevolentUnionType;
+use PHPStan\Type\DynamicMethodReturnTypeExtension;
+use PHPStan\Type\NullType;
+use PHPStan\Type\Type;
+use PHPStan\Type\TypeCombinator;
+use PHPStan\Type\TypeUtils;
+use function in_array;
+
+#[AutowiredService]
+final class IteratorCurrentReturnTypeExtension implements DynamicMethodReturnTypeExtension
+{
+
+	public function getClass(): string
+	{
+		return Iterator::class;
+	}
+
+	public function isMethodSupported(MethodReflection $methodReflection): bool
+	{
+		return in_array($methodReflection->getName(), ['current', 'key'], true);
+	}
+
+	public function getTypeFromMethodCall(MethodReflection $methodReflection, MethodCall $methodCall, Scope $scope): Type
+	{
+		$parametersAcceptor = ParametersAcceptorSelector::selectFromArgs(
+			$scope,
+			$methodCall->getArgs(),
+			$methodReflection->getVariants(),
+		);
+
+		$returnType = $parametersAcceptor->getReturnType();
+
+		if ($parametersAcceptor instanceof ExtendedParametersAcceptor) {
+			$nativeReturnType = $parametersAcceptor->getNativeReturnType();
+			if ($nativeReturnType->isSuperTypeOf(new NullType())->no()) {
+				return $returnType;
+			}
+		}
+
+		$result = TypeCombinator::addNull($returnType);
+		if ($returnType instanceof BenevolentUnionType && !($result instanceof BenevolentUnionType)) {
+			$result = TypeUtils::toBenevolentUnion($result);
+		}
+
+		return $result;
+	}
+
+}

src/Type/Php/IteratorValidMethodTypeSpecifyingExtension.php

@@ -0,0 +1,72 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Type\Php;
+
+use Iterator;
+use PhpParser\Node\Expr\MethodCall;
+use PhpParser\Node\Identifier;
+use PHPStan\Analyser\Scope;
+use PHPStan\Analyser\SpecifiedTypes;
+use PHPStan\Analyser\TypeSpecifier;
+use PHPStan\Analyser\TypeSpecifierAwareExtension;
+use PHPStan\Analyser\TypeSpecifierContext;
+use PHPStan\DependencyInjection\AutowiredService;
+use PHPStan\Reflection\MethodReflection;
+use PHPStan\Reflection\ParametersAcceptorSelector;
+use PHPStan\Type\MethodTypeSpecifyingExtension;
+
+#[AutowiredService]
+final class IteratorValidMethodTypeSpecifyingExtension implements MethodTypeSpecifyingExtension, TypeSpecifierAwareExtension
+{
+
+	private TypeSpecifier $typeSpecifier;
+
+	public function setTypeSpecifier(TypeSpecifier $typeSpecifier): void
+	{
+		$this->typeSpecifier = $typeSpecifier;
+	}
+
+	public function getClass(): string
+	{
+		return Iterator::class;
+	}
+
+	public function isMethodSupported(MethodReflection $methodReflection, MethodCall $node, TypeSpecifierContext $context): bool
+	{
+		return $methodReflection->getName() === 'valid'
+			&& $context->truthy();
+	}
+
+	public function specifyTypes(MethodReflection $methodReflection, MethodCall $node, Scope $scope, TypeSpecifierContext $context): SpecifiedTypes
+	{
+		$calledOnType = $scope->getType($node->var);
+		$types = new SpecifiedTypes();
+
+		foreach (['current', 'key'] as $methodName) {
+			$methodCallExpr = new MethodCall($node->var, new Identifier($methodName));
+
+			$targetMethodReflection = $scope->getMethodReflection($calledOnType, $methodName);
+			if ($targetMethodReflection === null) {
+				continue;
+			}
+
+			$parametersAcceptor = ParametersAcceptorSelector::selectFromArgs(
+				$scope,
+				[],
+				$targetMethodReflection->getVariants(),
+			);
+
+			$baseReturnType = $parametersAcceptor->getReturnType();
+
+			$types = $types->unionWith($this->typeSpecifier->create(
+				$methodCallExpr,
+				$baseReturnType,
+				TypeSpecifierContext::createTrue(),
+				$scope,
+			));
+		}
+
+		return $types;
+	}
+
+}