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Fix incorrect type inference for @phpstan-assert-if-true on $this with union types #4246

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Fix incorrect type inference for @phpstan-assert-if-true on $this with union types #4246

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ab74f12
test: reproduce #13358 (assert-if-true on $this lost via union)
potet Aug 17, 2025
1f1e916
fix(reflection): merge assertions in UnionTypeMethodReflection::getAs…
potet Aug 17, 2025
31b55ac
Move bug-13358 test to nsrt/ and remove obsolete test class
potet Aug 19, 2025
6ca93cf
Add regression test for #11441 (assert on UnionType)
yt-catpaw Aug 21, 2025
65ac9e0
Consistent variable name in getAsserts()
yt-catpaw Aug 21, 2025
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8 changes: 7 additions & 1 deletion src/Reflection/Type/UnionTypeMethodReflection.php
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Original file line number Diff line number Diff line change
Expand Up @@ -177,7 +177,13 @@ public function getDocComment(): ?string

public function getAsserts(): Assertions
{
return Assertions::createEmpty();
$assertions = Assertions::createEmpty();

foreach ($this->methods as $method) {
$assertions = $assertions->intersectWith($method->getAsserts());
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This will merge assertions from both types. Which is a wrong operation. (The method has a misleading name but it's used in IntersectionTypeMethodReflection where it's appropriate.)

In a union type what needs to be done is we need to look at assertions from all places and do some kind of intersection, figure out the common assertions.

Let's say we have Foo|Bar and we call a method that's on both types.

One method does some kind of assertion and the other method does a different assertion. The correct performed assertion on the union is none because they have nothing in common.

So we need to look at on which expression the assertion is performed (in this case $this->getParam()) and if all involved methods on the union are doing an assertion on the same expression.

Then we need to take a look at the asserted type and also take it into account only if it's the same. (It's possible that they don't have to be the same but we'd have to figure out the right operation that we can be sure about.)

}

return $assertions;
}

public function acceptsNamedArguments(): TrinaryLogic
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39 changes: 39 additions & 0 deletions tests/PHPStan/Analyser/nsrt/bug-11441.php
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@@ -0,0 +1,39 @@
<?php declare(strict_types=1);

namespace Bug11441;

use function PHPStan\Testing\assertType;

class Foo {
public function getParam(): ?string {
return 'foo';
}

/** @phpstan-assert !null $this->getParam() */
public function checkNotNull(): void {
if ($this->getParam() === null) {
throw new \Exception();
}
}
}

class Bar {
public function getParam(): ?int {
return 1;
}

/** @phpstan-assert !null $this->getParam() */
public function checkNotNull(): void {
if ($this->getParam() === null) {
throw new \Exception();
}
}
}

function test(Foo|Bar $obj): void {
assertType('int|string|null', $obj->getParam());

$obj->checkNotNull();

assertType('int|string', $obj->getParam());
}
40 changes: 40 additions & 0 deletions tests/PHPStan/Analyser/nsrt/bug-13358.php
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@@ -0,0 +1,40 @@
<?php declare(strict_types=1);

namespace Bug13358;

use function PHPStan\Testing\assertType;

/**
* @phpstan-sealed SystemActor|AnonymousVisitorActor
*/
abstract class Actor
{
/**
* @phpstan-assert-if-true SystemActor $this
*/
public function isSystem(): bool
{
return $this instanceof SystemActor;
}

/**
* @phpstan-assert-if-true AnonymousVisitorActor $this
*/
public function isAnonymousVisitor(): bool
{
return $this instanceof AnonymousVisitorActor;
}
}

class SystemActor extends Actor {}
class AnonymousVisitorActor extends Actor {}

function test(AnonymousVisitorActor|SystemActor $actor): void {
assertType('Bug13358\AnonymousVisitorActor|Bug13358\SystemActor', $actor);

if ($actor->isSystem()) {
assertType('Bug13358\SystemActor', $actor);
} else {
assertType('Bug13358\AnonymousVisitorActor', $actor);
}
}
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