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Fix phpstan/phpstan#14211: incorrect type inference with dependent types #5092

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Fix phpstan/phpstan#14211: incorrect type inference with dependent types #5092

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10 changes: 9 additions & 1 deletion src/Analyser/MutatingScope.php
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Original file line number Diff line number Diff line change
Expand Up @@ -3833,7 +3833,15 @@ public function filterBySpecifiedTypes(SpecifiedTypes $specifiedTypes): self
}

$conditions[$conditionalExprString][] = $conditionalExpression;
$specifiedExpressions[$conditionalExprString] = $conditionalExpression->getTypeHolder();
$newTypeHolder = $conditionalExpression->getTypeHolder();
if (array_key_exists($conditionalExprString, $specifiedExpressions) && $specifiedExpressions[$conditionalExprString]->getCertainty()->yes() && $newTypeHolder->getCertainty()->yes()) {
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@VincentLanglet VincentLanglet Feb 28, 2026

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It's unclear to me why we're only concerned about Yes & Yes.

Looking at this code, the last newTypeHolder override all the previous one if there is some Maybe certainty in the game.

Is this condition clear to you @staabm ?

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@VincentLanglet VincentLanglet Mar 1, 2026

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Updating the code to

if (array_key_exists($conditionalExprString, $specifiedExpressions)) {

does not creates any failure. I feel like we're lacking of coverage. But I never worked with ExpressionTypeHolder...

$specifiedExpressions[$conditionalExprString] = ExpressionTypeHolder::createYes(
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@VincentLanglet VincentLanglet Mar 1, 2026

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ExpressionTypeHolder has a method and

public function and(self $other): self
	{
		if ($this->type === $other->type || $this->type->equals($other->type)) {
			if ($this->certainty->and($other->certainty)->yes()) {
				return $this;
			}

			if ($this->certainty->maybe()) {
				return $this;
			}

			return $other;
		}

		return new self(
			$this->expr,
			TypeCombinator::union($this->type, $other->type),
			$this->certainty->and($other->certainty),
		);
	}

Should we introduce a new method for ExpressionTypeHolder which does the intersect ?

$newTypeHolder->getExpr(),
TypeCombinator::intersect($specifiedExpressions[$conditionalExprString]->getType(), $newTypeHolder->getType()),
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@VincentLanglet VincentLanglet Feb 28, 2026

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This might add a lot of possibly useless intersect calls.

For instance if the next newTypeHolder does not have a certainty of Yes. we will override the value.

Might be better to check it first by computing all the newTypeHolder and

  • if they all have a yes certainty we intersect them
  • if not, we take the last one

WDYT @staabm ?

);
} else {
$specifiedExpressions[$conditionalExprString] = $newTypeHolder;
}
}
}
}
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25 changes: 25 additions & 0 deletions tests/PHPStan/Analyser/nsrt/bug-14211.php
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Original file line number Diff line number Diff line change
@@ -0,0 +1,25 @@
<?php declare(strict_types=1);

namespace Bug14211;

use function PHPStan\Testing\assertType;

/** @param array<mixed> $data */
function doSomething(array $data): bool {

if (!isset($data['x']))
return false;

$m = isset($data['y']);

if ($m) {
assertType('true', $m);
}
assertType('bool', $m);

if ($m) {
assertType('true', $m);
}

return true;
}
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