Include null in return type of Closure::bindTo() and Closure::bind() dynamic return type extensions

src/Analyser/ExprHandler/Helper/ClosureTypeResolver.php

@@ -220,13 +220,15 @@ static function (Node $node, Scope $scope) use ($arrowScope, &$arrowFunctionImpu
 					usedVariables: $cachedClosureData['usedVariables'],
 					acceptsNamedArguments: TrinaryLogic::createYes(),
 					mustUseReturnValue: $mustUseReturnValue,
+					isStatic: TrinaryLogic::createFromBoolean($expr->static),
 				);
 			}
 			if (self::$resolveClosureTypeDepth >= 2) {
 				return new ClosureType(
 					$parameters,
 					$scope->getFunctionType($expr->returnType, false, false),
 					$isVariadic,
+					isStatic: TrinaryLogic::createFromBoolean($expr->static),
 				);
 			}
 
@@ -446,6 +448,7 @@ static function (Node $node, Scope $scope) use ($arrowScope, &$arrowFunctionImpu
 			usedVariables: $usedVariables,
 			acceptsNamedArguments: TrinaryLogic::createYes(),
 			mustUseReturnValue: $mustUseReturnValue,
+			isStatic: TrinaryLogic::createFromBoolean($expr->static),
 		);
 	}
 

src/Reflection/InitializerExprTypeResolver.php

@@ -263,6 +263,7 @@ public function getType(Expr $expr, InitializerExprContext $context): Type
 				TemplateTypeMap::createEmpty(),
 				TemplateTypeVarianceMap::createEmpty(),
 				acceptsNamedArguments: TrinaryLogic::createYes(),
+				isStatic: TrinaryLogic::createYes(),
 			);
 		}
 		if ($expr instanceof Expr\ArrayDimFetch && $expr->dim !== null) {

src/Type/ClosureType.php

@@ -88,6 +88,8 @@ class ClosureType implements TypeWithClassName, CallableParametersAcceptor
 
 	private Assertions $assertions;
 
+	private TrinaryLogic $isStatic;
+
 	/**
 	 * @api
 	 * @param list<ParameterReflection>|null $parameters
@@ -112,6 +114,7 @@ public function __construct(
 		?TrinaryLogic $acceptsNamedArguments = null,
 		?TrinaryLogic $mustUseReturnValue = null,
 		?Assertions $assertions = null,
+		?TrinaryLogic $isStatic = null,
 	)
 	{
 		if ($acceptsNamedArguments === null) {
@@ -132,6 +135,7 @@ public function __construct(
 		$this->callSiteVarianceMap = $callSiteVarianceMap ?? TemplateTypeVarianceMap::createEmpty();
 		$this->impurePoints = $impurePoints ?? [new SimpleImpurePoint('functionCall', 'call to an unknown Closure', false)];
 		$this->assertions = $assertions ?? Assertions::createEmpty();
+		$this->isStatic = $isStatic ?? TrinaryLogic::createMaybe();
 	}
 
 	public function getAsserts(): Assertions
@@ -302,6 +306,7 @@ function (): string {
 					$this->usedVariables,
 					$this->acceptsNamedArguments,
 					$this->mustUseReturnValue,
+					isStatic: $this->isStatic,
 				);
 
 				return $printer->print($selfWithoutParameterNames->toPhpDocNode());
@@ -461,6 +466,11 @@ public function isCommonCallable(): bool
 		return $this->isCommonCallable;
 	}
 
+	public function isStaticClosure(): TrinaryLogic
+	{
+		return $this->isStatic;
+	}
+
 	public function getCallableParametersAcceptors(ClassMemberAccessAnswerer $scope): array
 	{
 		return [$this];
@@ -709,6 +719,7 @@ public function traverse(callable $cb): Type
 			$this->acceptsNamedArguments,
 			$this->mustUseReturnValue,
 			$this->assertions,
+			$this->isStatic,
 		);
 	}
 
@@ -761,6 +772,7 @@ public function traverseSimultaneously(Type $right, callable $cb): Type
 			$this->acceptsNamedArguments,
 			$this->mustUseReturnValue,
 			$this->assertions,
+			$this->isStatic,
 		);
 	}
 

src/Type/Php/ClosureBindDynamicReturnTypeExtension.php

@@ -7,8 +7,10 @@
 use PHPStan\Analyser\Scope;
 use PHPStan\DependencyInjection\AutowiredService;
 use PHPStan\Reflection\MethodReflection;
+use PHPStan\Type\BenevolentUnionType;
 use PHPStan\Type\ClosureType;
 use PHPStan\Type\DynamicStaticMethodReturnTypeExtension;
+use PHPStan\Type\NullType;
 use PHPStan\Type\Type;
 
 #[AutowiredService]
@@ -27,12 +29,21 @@
 
 	public function getTypeFromStaticMethodCall(MethodReflection $methodReflection, StaticCall $methodCall, Scope $scope): ?Type
 	{
-		$closureType = $scope->getType($methodCall->getArgs()[0]->value);
+		$args = $methodCall->getArgs();
+		$closureType = $scope->getType($args[0]->value);
 		if (!($closureType instanceof ClosureType)) {
 			return null;
 		}
 
-		return $closureType;
+		if ($closureType->isStaticClosure()->no()) {
+			return $closureType;
+		}
+
+		if (isset($args[1]) && $scope->getType($args[1]->value)->isNull()->yes()) {
+			return $closureType;
+		}
+
+		return new BenevolentUnionType([$closureType, new NullType()]);
 	}
 
 }

src/Type/Php/ClosureBindToDynamicReturnTypeExtension.php

@@ -7,8 +7,10 @@
 use PHPStan\Analyser\Scope;
 use PHPStan\DependencyInjection\AutowiredService;
 use PHPStan\Reflection\MethodReflection;
+use PHPStan\Type\BenevolentUnionType;
 use PHPStan\Type\ClosureType;
 use PHPStan\Type\DynamicMethodReturnTypeExtension;
+use PHPStan\Type\NullType;
 use PHPStan\Type\Type;
 
 #[AutowiredService]
@@ -32,7 +34,16 @@ public function getTypeFromMethodCall(MethodReflection $methodReflection, Method
 			return null;
 		}
 
-		return $closureType;
+		if ($closureType->isStaticClosure()->no()) {
+			return $closureType;
+		}
+
+		$args = $methodCall->getArgs();
+		if (isset($args[0]) && $scope->getType($args[0]->value)->isNull()->yes()) {
+			return $closureType;
+		}
+
+		return new BenevolentUnionType([$closureType, new NullType()]);
 	}
 
 }

tests/PHPStan/Analyser/nsrt/bug-5009.php

@@ -0,0 +1,46 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace Bug5009;
+
+use Closure;
+use function PHPStan\Testing\assertType;
+
+$foo = function (): void {};
+$bar = $foo->bindTo(null);
+assertType('Closure(): void', $bar);
+
+$baz = Closure::bind($foo, null);
+assertType('Closure(): void', $baz);
+
+$newThis = new \stdClass();
+$bound = $foo->bindTo($newThis);
+assertType('Closure(): void', $bound);
+
+$staticBound = Closure::bind($foo, $newThis);
+assertType('Closure(): void', $staticBound);
+
+$bound2 = $foo->bindTo($newThis, 'stdClass');
+assertType('Closure(): void', $bound2);
+
+$static = static function (): void {};
+$boundStatic = $static->bindTo($newThis);
+assertType('((Closure(): void)|null)', $boundStatic);
+
+$boundStaticNull = $static->bindTo(null);
+assertType('Closure(): void', $boundStaticNull);
+
+$staticBound2 = Closure::bind($static, $newThis);
+assertType('((Closure(): void)|null)', $staticBound2);
+
+$staticBoundNull = Closure::bind($static, null);
+assertType('Closure(): void', $staticBoundNull);
+
+/** @var \stdClass|null $maybeNull */
+$maybeNull = null;
+$boundMaybe = $foo->bindTo($maybeNull);
+assertType('Closure(): void', $boundMaybe);
+
+$staticBoundMaybe = $static->bindTo($maybeNull);
+assertType('((Closure(): void)|null)', $staticBoundMaybe);

tests/PHPStan/Analyser/nsrt/closure-return-type-extensions.php

@@ -11,13 +11,13 @@
 
 $newThis = new class {};
 $boundClosure = $closure->bindTo($newThis);
-assertType('Closure(object): true', $boundClosure);
+assertType('((Closure(object): true)|null)', $boundClosure);
 
 $staticallyBoundClosure = \Closure::bind($closure, $newThis);
-assertType('Closure(object): true', $staticallyBoundClosure);
+assertType('((Closure(object): true)|null)', $staticallyBoundClosure);
 
 $returnType = $closure->call($newThis, new class {});
 assertType('true', $returnType);
 
 $staticallyBoundClosureCaseInsensitive = \closure::bind($closure, $newThis);
-assertType('Closure(object): true', $staticallyBoundClosureCaseInsensitive);
+assertType('((Closure(object): true)|null)', $staticallyBoundClosureCaseInsensitive);