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multiply by zero is always zero #974

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merged 3 commits into from Feb 6, 2022
Merged

multiply by zero is always zero #974

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9f941cc
multiply by zero is always zero
clxmstaab Feb 1, 2022
66a70ab
fix floats
staabm Feb 1, 2022
4716eb7
cover bool false
staabm Feb 1, 2022
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18 changes: 18 additions & 0 deletions src/Analyser/MutatingScope.php
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Expand Up @@ -1040,6 +1040,24 @@ private function resolveType(Expr $node): Type
return new StringType();
}

if (
$node instanceof Node\Expr\BinaryOp\Mul
|| $node instanceof Node\Expr\AssignOp\Mul
) {
if ($node instanceof Node\Expr\AssignOp) {
$leftType = null;
$rightType = $this->getType($node->expr);
} else {
$leftType = $this->getType($node->left);
$rightType = $this->getType($node->right);
}

if ($leftType instanceof ConstantIntegerType && $leftType->getValue() === 0 ||
$rightType instanceof ConstantIntegerType && $rightType->getValue() === 0) {
return new ConstantIntegerType(0);
}
}

if (
$node instanceof Node\Expr\BinaryOp\Div
|| $node instanceof Node\Expr\AssignOp\Div
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22 changes: 22 additions & 0 deletions tests/PHPStan/Analyser/data/math.php
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Expand Up @@ -109,4 +109,26 @@ public function doSit(int $i, int $j): void
assertType('int', $i - $j);
}

/**
* @param int<-5, 5> $range
*/
public function multiplyZero(int $i, float $f, $range): void
{
assertType('0', $i * 0);
assertType('0', $f * 0);
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Float multiplied by zero is a float: https://3v4l.org/u6dA6

It also works for strings: https://3v4l.org/Ksheh

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good catch. fixed

assertType('0', $range * 0);

assertType('0', 0 * $i);
assertType('0', 0 * $f);
assertType('0', 0 * $range);

$i *= 0;
$f *= 0;
$range *= 0;
assertType('0', $i);
assertType('0', $f);
assertType('0', $range);

}

}