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Fix phpstan/phpstan#5952: Allow throwing exceptions from __toString() not detected since level 4 #5405

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Merged
VincentLanglet merged 7 commits into from
Apr 7, 2026
Merged

Fix phpstan/phpstan#5952: Allow throwing exceptions from __toString() not detected since level 4 #5405

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01f336d
Fix phpstan/phpstan#5952: Track __toString() throws in echo statements
VincentLanglet Apr 5, 2026
546a487
Simulate MethodCall instead of calling MethodThrowPointHelper directly
phpstan-bot Apr 5, 2026
a39518e
Remove redundant phpVersion check and add union type tests
phpstan-bot Apr 5, 2026
a85d75b
Generalize __toString() throw point tracking to all implicit call sites
phpstan-bot Apr 5, 2026
879b943
Rename ToStringThrowPointHelper to ImplicitToStringCallHelper and ret…
phpstan-bot Apr 6, 2026
281d039
Use import statement for ImplicitToStringCallHelper instead of fully …
phpstan-bot Apr 6, 2026
0e0de1c
Collect impure points from implicit __toString() in echo handler and …
phpstan-bot Apr 6, 2026
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11 changes: 10 additions & 1 deletion src/Analyser/ExprHandler/AssignOpHandler.php
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,7 @@
use PHPStan\Analyser\ExpressionResult;
use PHPStan\Analyser\ExpressionResultStorage;
use PHPStan\Analyser\ExprHandler;
use PHPStan\Analyser\ExprHandler\Helper\ImplicitToStringCallHelper;
use PHPStan\Analyser\InternalThrowPoint;
use PHPStan\Analyser\MutatingScope;
use PHPStan\Analyser\NodeScopeResolver;
Expand All @@ -22,6 +23,7 @@
use PHPStan\Type\Constant\ConstantIntegerType;
use PHPStan\Type\ObjectType;
use PHPStan\Type\Type;
use function array_merge;
use function get_class;
use function sprintf;

Expand All @@ -35,6 +37,7 @@ final class AssignOpHandler implements ExprHandler
public function __construct(
private AssignHandler $assignHandler,
private InitializerExprTypeResolver $initializerExprTypeResolver,
private ImplicitToStringCallHelper $implicitToStringCallHelper,
)
{
}
Expand Down Expand Up @@ -85,19 +88,25 @@ static function (MutatingScope $scope) use ($stmt, $expr, $nodeCallback, $contex
}
$scope = $assignResult->getScope();
$throwPoints = $assignResult->getThrowPoints();
$impurePoints = $assignResult->getImpurePoints();
if (
($expr instanceof Expr\AssignOp\Div || $expr instanceof Expr\AssignOp\Mod) &&
!$scope->getType($expr->expr)->toNumber()->isSuperTypeOf(new ConstantIntegerType(0))->no()
) {
$throwPoints[] = InternalThrowPoint::createExplicit($scope, new ObjectType(DivisionByZeroError::class), $expr, false);
}
if ($expr instanceof Expr\AssignOp\Concat) {
$toStringResult = $this->implicitToStringCallHelper->processImplicitToStringCall($expr->expr, $scope);
$throwPoints = array_merge($throwPoints, $toStringResult->getThrowPoints());
$impurePoints = array_merge($impurePoints, $toStringResult->getImpurePoints());
}

return new ExpressionResult(
$scope,
hasYield: $assignResult->hasYield(),
isAlwaysTerminating: $assignResult->isAlwaysTerminating(),
throwPoints: $throwPoints,
impurePoints: $assignResult->getImpurePoints(),
impurePoints: $impurePoints,
truthyScopeCallback: static fn (): MutatingScope => $scope->filterByTruthyValue($expr),
falseyScopeCallback: static fn (): MutatingScope => $scope->filterByFalseyValue($expr),
);
Expand Down
11 changes: 10 additions & 1 deletion src/Analyser/ExprHandler/BinaryOpHandler.php
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Expand Up @@ -13,6 +13,7 @@
use PHPStan\Analyser\ExpressionResult;
use PHPStan\Analyser\ExpressionResultStorage;
use PHPStan\Analyser\ExprHandler;
use PHPStan\Analyser\ExprHandler\Helper\ImplicitToStringCallHelper;
use PHPStan\Analyser\InternalThrowPoint;
use PHPStan\Analyser\MutatingScope;
use PHPStan\Analyser\NodeScopeResolver;
Expand Down Expand Up @@ -42,6 +43,7 @@ public function __construct(
private InitializerExprTypeResolver $initializerExprTypeResolver,
private RicherScopeGetTypeHelper $richerScopeGetTypeHelper,
private PhpVersion $phpVersion,
private ImplicitToStringCallHelper $implicitToStringCallHelper,
)
{
}
Expand All @@ -62,20 +64,27 @@ public function processExpr(NodeScopeResolver $nodeScopeResolver, Stmt $stmt, Ex
$leftResult = $nodeScopeResolver->processExprNode($stmt, $expr->left, $scope, $storage, $nodeCallback, $context->enterDeep());
$rightResult = $nodeScopeResolver->processExprNode($stmt, $expr->right, $leftResult->getScope(), $storage, $nodeCallback, $context->enterDeep());
$throwPoints = array_merge($leftResult->getThrowPoints(), $rightResult->getThrowPoints());
$impurePoints = array_merge($leftResult->getImpurePoints(), $rightResult->getImpurePoints());
if (
($expr instanceof BinaryOp\Div || $expr instanceof BinaryOp\Mod) &&
!$leftResult->getScope()->getType($expr->right)->toNumber()->isSuperTypeOf(new ConstantIntegerType(0))->no()
) {
$throwPoints[] = InternalThrowPoint::createExplicit($leftResult->getScope(), new ObjectType(DivisionByZeroError::class), $expr, false);
}
if ($expr instanceof BinaryOp\Concat) {
$leftToStringResult = $this->implicitToStringCallHelper->processImplicitToStringCall($expr->left, $scope);
$rightToStringResult = $this->implicitToStringCallHelper->processImplicitToStringCall($expr->right, $leftResult->getScope());
$throwPoints = array_merge($throwPoints, $leftToStringResult->getThrowPoints(), $rightToStringResult->getThrowPoints());
$impurePoints = array_merge($impurePoints, $leftToStringResult->getImpurePoints(), $rightToStringResult->getImpurePoints());
}
$scope = $rightResult->getScope();

return new ExpressionResult(
$scope,
hasYield: $leftResult->hasYield() || $rightResult->hasYield(),
isAlwaysTerminating: $leftResult->isAlwaysTerminating() || $rightResult->isAlwaysTerminating(),
throwPoints: $throwPoints,
impurePoints: array_merge($leftResult->getImpurePoints(), $rightResult->getImpurePoints()),
impurePoints: $impurePoints,
truthyScopeCallback: static fn (): MutatingScope => $scope->filterByTruthyValue($expr),
falseyScopeCallback: static fn (): MutatingScope => $scope->filterByFalseyValue($expr),
);
Expand Down
38 changes: 6 additions & 32 deletions src/Analyser/ExprHandler/CastStringHandler.php
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Original file line number Diff line number Diff line change
Expand Up @@ -4,21 +4,18 @@

use PhpParser\Node\Expr;
use PhpParser\Node\Expr\Cast;
use PhpParser\Node\Identifier;
use PhpParser\Node\Stmt;
use PHPStan\Analyser\ExpressionContext;
use PHPStan\Analyser\ExpressionResult;
use PHPStan\Analyser\ExpressionResultStorage;
use PHPStan\Analyser\ExprHandler;
use PHPStan\Analyser\ExprHandler\Helper\MethodThrowPointHelper;
use PHPStan\Analyser\ImpurePoint;
use PHPStan\Analyser\ExprHandler\Helper\ImplicitToStringCallHelper;
use PHPStan\Analyser\MutatingScope;
use PHPStan\Analyser\NodeScopeResolver;
use PHPStan\DependencyInjection\AutowiredService;
use PHPStan\Php\PhpVersion;
use PHPStan\Reflection\InitializerExprTypeResolver;
use PHPStan\Type\Type;
use function sprintf;
use function array_merge;

/**
* @implements ExprHandler<Cast\String_>
Expand All @@ -29,8 +26,7 @@ final class CastStringHandler implements ExprHandler

public function __construct(
private InitializerExprTypeResolver $initializerExprTypeResolver,
private PhpVersion $phpVersion,
private MethodThrowPointHelper $methodThrowPointHelper,
private ImplicitToStringCallHelper $implicitToStringCallHelper,
)
{
}
Expand All @@ -46,31 +42,9 @@ public function processExpr(NodeScopeResolver $nodeScopeResolver, Stmt $stmt, Ex
$impurePoints = $exprResult->getImpurePoints();
$throwPoints = $exprResult->getThrowPoints();

$exprType = $scope->getType($expr->expr);
$toStringMethod = $scope->getMethodReflection($exprType, '__toString');
if ($toStringMethod !== null) {
if (!$toStringMethod->hasSideEffects()->no()) {
$impurePoints[] = new ImpurePoint(
$scope,
$expr,
'methodCall',
sprintf('call to method %s::%s()', $toStringMethod->getDeclaringClass()->getDisplayName(), $toStringMethod->getName()),
$toStringMethod->isPure()->no(),
);
}

if ($this->phpVersion->throwsOnStringCast()) {
$throwPoint = $this->methodThrowPointHelper->getThrowPoint(
$toStringMethod,
$toStringMethod->getOnlyVariant(),
new Expr\MethodCall($expr->expr, new Identifier('__toString')),
$scope,
);
if ($throwPoint !== null) {
$throwPoints[] = $throwPoint;
}
}
}
$toStringResult = $this->implicitToStringCallHelper->processImplicitToStringCall($expr->expr, $scope);
$throwPoints = array_merge($throwPoints, $toStringResult->getThrowPoints());
$impurePoints = array_merge($impurePoints, $toStringResult->getImpurePoints());

$scope = $exprResult->getScope();

Expand Down
73 changes: 73 additions & 0 deletions src/Analyser/ExprHandler/Helper/ImplicitToStringCallHelper.php
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@@ -0,0 +1,73 @@
<?php declare(strict_types = 1);

namespace PHPStan\Analyser\ExprHandler\Helper;

use PhpParser\Node\Expr;
use PhpParser\Node\Identifier;
use PHPStan\Analyser\ExpressionResult;
use PHPStan\Analyser\ImpurePoint;
use PHPStan\Analyser\MutatingScope;
use PHPStan\DependencyInjection\AutowiredService;
use PHPStan\Php\PhpVersion;
use function sprintf;

#[AutowiredService]
final class ImplicitToStringCallHelper
{

public function __construct(
private PhpVersion $phpVersion,
private MethodThrowPointHelper $methodThrowPointHelper,
)
{
}

public function processImplicitToStringCall(Expr $expr, MutatingScope $scope): ExpressionResult
{
$throwPoints = [];
$impurePoints = [];

$exprType = $scope->getType($expr);
$toStringMethod = $scope->getMethodReflection($exprType, '__toString');
if ($toStringMethod === null) {
return new ExpressionResult(
$scope,
hasYield: false,
isAlwaysTerminating: false,
throwPoints: [],
impurePoints: [],
);
}

if (!$toStringMethod->hasSideEffects()->no()) {
$impurePoints[] = new ImpurePoint(
$scope,
$expr,
'methodCall',
sprintf('call to method %s::%s()', $toStringMethod->getDeclaringClass()->getDisplayName(), $toStringMethod->getName()),
$toStringMethod->isPure()->no(),
);
}

if ($this->phpVersion->throwsOnStringCast()) {
$throwPoint = $this->methodThrowPointHelper->getThrowPoint(
$toStringMethod,
$toStringMethod->getOnlyVariant(),
new Expr\MethodCall($expr, new Identifier('__toString')),
$scope,
);
if ($throwPoint !== null) {
$throwPoints[] = $throwPoint;
}
}

return new ExpressionResult(
$scope,
hasYield: false,
isAlwaysTerminating: false,
throwPoints: $throwPoints,
impurePoints: $impurePoints,
);
}

}
7 changes: 7 additions & 0 deletions src/Analyser/ExprHandler/InterpolatedStringHandler.php
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,7 @@
use PHPStan\Analyser\ExpressionResult;
use PHPStan\Analyser\ExpressionResultStorage;
use PHPStan\Analyser\ExprHandler;
use PHPStan\Analyser\ExprHandler\Helper\ImplicitToStringCallHelper;
use PHPStan\Analyser\MutatingScope;
use PHPStan\Analyser\NodeScopeResolver;
use PHPStan\DependencyInjection\AutowiredService;
Expand All @@ -27,6 +28,7 @@ final class InterpolatedStringHandler implements ExprHandler

public function __construct(
private InitializerExprTypeResolver $initializerExprTypeResolver,
private ImplicitToStringCallHelper $implicitToStringCallHelper,
)
{
}
Expand All @@ -50,6 +52,11 @@ public function processExpr(NodeScopeResolver $nodeScopeResolver, Stmt $stmt, Ex
$hasYield = $hasYield || $partResult->hasYield();
$throwPoints = array_merge($throwPoints, $partResult->getThrowPoints());
$impurePoints = array_merge($impurePoints, $partResult->getImpurePoints());

$toStringResult = $this->implicitToStringCallHelper->processImplicitToStringCall($part, $scope);
$throwPoints = array_merge($throwPoints, $toStringResult->getThrowPoints());
$impurePoints = array_merge($impurePoints, $toStringResult->getImpurePoints());

$isAlwaysTerminating = $isAlwaysTerminating || $partResult->isAlwaysTerminating();
$scope = $partResult->getScope();
}
Expand Down
18 changes: 16 additions & 2 deletions src/Analyser/ExprHandler/PrintHandler.php
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Expand Up @@ -9,6 +9,7 @@
use PHPStan\Analyser\ExpressionResult;
use PHPStan\Analyser\ExpressionResultStorage;
use PHPStan\Analyser\ExprHandler;
use PHPStan\Analyser\ExprHandler\Helper\ImplicitToStringCallHelper;
use PHPStan\Analyser\ImpurePoint;
use PHPStan\Analyser\MutatingScope;
use PHPStan\Analyser\NodeScopeResolver;
Expand All @@ -24,6 +25,12 @@
final class PrintHandler implements ExprHandler
{

public function __construct(
private ImplicitToStringCallHelper $implicitToStringCallHelper,
)
{
}

public function supports(Expr $expr): bool
{
return $expr instanceof Print_;
Expand All @@ -37,14 +44,21 @@ public function resolveType(MutatingScope $scope, Expr $expr): Type
public function processExpr(NodeScopeResolver $nodeScopeResolver, Stmt $stmt, Expr $expr, MutatingScope $scope, ExpressionResultStorage $storage, callable $nodeCallback, ExpressionContext $context): ExpressionResult
{
$exprResult = $nodeScopeResolver->processExprNode($stmt, $expr->expr, $scope, $storage, $nodeCallback, $context->enterDeep());
$throwPoints = $exprResult->getThrowPoints();
$impurePoints = $exprResult->getImpurePoints();

$toStringResult = $this->implicitToStringCallHelper->processImplicitToStringCall($expr->expr, $scope);
$throwPoints = array_merge($throwPoints, $toStringResult->getThrowPoints());
$impurePoints = array_merge($impurePoints, $toStringResult->getImpurePoints());
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@staabm staabm Apr 6, 2026

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this PR is not only about throw points, but also impure points.

it seems the impurity portion does not have tests

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@phpstan-bot phpstan-bot Apr 6, 2026

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Both background tasks confirmed complete. Everything was already pushed — nothing more needed.


$scope = $exprResult->getScope();

return new ExpressionResult(
$scope,
hasYield: $exprResult->hasYield(),
isAlwaysTerminating: $exprResult->isAlwaysTerminating(),
throwPoints: $exprResult->getThrowPoints(),
impurePoints: array_merge($exprResult->getImpurePoints(), [new ImpurePoint($scope, $expr, 'print', 'print', true)]),
throwPoints: $throwPoints,
impurePoints: array_merge($impurePoints, [new ImpurePoint($scope, $expr, 'print', 'print', true)]),
);
}

Expand Down
11 changes: 8 additions & 3 deletions src/Analyser/NodeScopeResolver.php
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Expand Up @@ -49,6 +49,7 @@
use PhpParser\NodeTraverser;
use PhpParser\NodeVisitorAbstract;
use PHPStan\Analyser\ExprHandler\AssignHandler;
use PHPStan\Analyser\ExprHandler\Helper\ImplicitToStringCallHelper;
use PHPStan\BetterReflection\Reflection\Adapter\ReflectionClass;
use PHPStan\BetterReflection\Reflection\ReflectionEnum;
use PHPStan\BetterReflection\Reflector\Reflector;
Expand Down Expand Up @@ -236,6 +237,7 @@ public function __construct(
private readonly bool $implicitThrows,
#[AutowiredParameter]
private readonly bool $treatPhpDocTypesAsCertain,
private readonly ImplicitToStringCallHelper $implicitToStringCallHelper,
)
{
$earlyTerminatingMethodNames = [];
Expand Down Expand Up @@ -861,19 +863,22 @@ public function processStmtNode(
} elseif ($stmt instanceof Echo_) {
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@staabm staabm Apr 7, 2026

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do we need more changes in NodeScopeResolver to reflect the changes made in ExprHandler classes with this PR?

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@phpstan-bot phpstan-bot Apr 7, 2026

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All 11732 tests pass.

Summary: After analyzing the codebase, no additional changes are needed in NodeScopeResolver.php. Here's why:

  • The echo handler (line 872) already correctly uses ImplicitToStringCallHelper — this was added in this PR
  • All other implicit __toString() call sites are expressions (not statements), so they're handled by their respective ExprHandler classes:
    • PrintHandler — print $obj
    • CastStringHandler — (string) $obj
    • BinaryOpHandler — 'hello' . $obj
    • AssignOpHandler — $x .= $obj
    • InterpolatedStringHandler — "hello $obj"

The ImplicitToStringCallHelper is injected into NodeScopeResolver solely for the echo statement, since echo is a Stmt (not an Expr) and cannot have its own ExprHandler.

I was unable to post this reply as a PR comment due to GitHub token permissions. You may want to reply to staabm's comment manually with this explanation.

$hasYield = false;
$throwPoints = [];
$impurePoints = [];
$isAlwaysTerminating = false;
foreach ($stmt->exprs as $echoExpr) {
$result = $this->processExprNode($stmt, $echoExpr, $scope, $storage, $nodeCallback, ExpressionContext::createDeep());
$throwPoints = array_merge($throwPoints, $result->getThrowPoints());
$impurePoints = array_merge($impurePoints, $result->getImpurePoints());
$toStringResult = $this->implicitToStringCallHelper->processImplicitToStringCall($echoExpr, $scope);
$throwPoints = array_merge($throwPoints, $toStringResult->getThrowPoints());
$impurePoints = array_merge($impurePoints, $toStringResult->getImpurePoints());
$scope = $result->getScope();
$hasYield = $hasYield || $result->hasYield();
$isAlwaysTerminating = $isAlwaysTerminating || $result->isAlwaysTerminating();
}

$throwPoints = $overridingThrowPoints ?? $throwPoints;
$impurePoints = [
new ImpurePoint($scope, $stmt, 'echo', 'echo', true),
];
$impurePoints[] = new ImpurePoint($scope, $stmt, 'echo', 'echo', true);
return new InternalStatementResult($scope, $hasYield, $isAlwaysTerminating, [], $throwPoints, $impurePoints);
} elseif ($stmt instanceof Return_) {
if ($stmt->expr !== null) {
Expand Down
2 changes: 2 additions & 0 deletions src/Testing/RuleTestCase.php
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Expand Up @@ -6,6 +6,7 @@
use PHPStan\Analyser\Analyser;
use PHPStan\Analyser\AnalyserResultFinalizer;
use PHPStan\Analyser\Error;
use PHPStan\Analyser\ExprHandler\Helper\ImplicitToStringCallHelper;
use PHPStan\Analyser\Fiber\FiberNodeScopeResolver;
use PHPStan\Analyser\FileAnalyser;
use PHPStan\Analyser\IgnoreErrorExtensionProvider;
Expand Down Expand Up @@ -116,6 +117,7 @@ protected function createNodeScopeResolver(): NodeScopeResolver
[],
self::getContainer()->getParameter('exceptions')['implicitThrows'],
$this->shouldTreatPhpDocTypesAsCertain(),
self::getContainer()->getByType(ImplicitToStringCallHelper::class),
);
}

Expand Down
2 changes: 2 additions & 0 deletions src/Testing/TypeInferenceTestCase.php
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Expand Up @@ -6,6 +6,7 @@
use PhpParser\Node;
use PhpParser\Node\Expr\StaticCall;
use PhpParser\Node\Name;
use PHPStan\Analyser\ExprHandler\Helper\ImplicitToStringCallHelper;
use PHPStan\Analyser\Fiber\FiberNodeScopeResolver;
use PHPStan\Analyser\MutatingScope;
use PHPStan\Analyser\NodeScopeResolver;
Expand Down Expand Up @@ -91,6 +92,7 @@ protected static function createNodeScopeResolver(): NodeScopeResolver
static::getEarlyTerminatingFunctionCalls(),
$container->getParameter('exceptions')['implicitThrows'],
$container->getParameter('treatPhpDocTypesAsCertain'),
$container->getByType(ImplicitToStringCallHelper::class),
);
}

Expand Down
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